6713442 ceramic-arts-handbook


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6713442 ceramic-arts-handbook

  1. 1. Ceramic Arts Handbook by Vince Pitelkawww.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society
  2. 2. Ta b l e o f C o n t e n t s Preface..........................................................................................   1 1 Clay and Claybodies. .............................................................   3 . The Nature of Clay.................................................................................  3 Claybodies ..............................................................................................  4 2 Handbuilding.........................................................................  5 . Wedging the Clay..................................................................................  6 Handbuilding: General Guidelines and Suggestions..................................................................................  6 Making Pinch Forms..............................................................................  9 Coil Construction................................................................................   11 Slab Construction. ..............................................................................   14 . Making Tiles........................................................................................   17 3 Throwing..............................................................................  19 Critical Points in Throwing.................................................................   19 Skill Development with Cylinders......................................................   21 Throwing Bowls..................................................................................   22 Drying Your Pots.................................................................................   26 Finishing the Bottoms of Your Pots...................................................   27 4 Surface Decoration on Greenware.....................................  29 . Decorative Effects during Forming....................................................   29 Impressed Decoration. .......................................................................   29 . Subtractive Methods. .........................................................................   31 . Additive Methods...............................................................................   32 . 5 Glazes and Glazing..............................................................  33 Introduction to Glazing......................................................................   33 Glaze-Firing Ranges............................................................................   34 Glazing Methods. ...............................................................................   34 . Glaze Faults.........................................................................................   36 6 Kilns and Firing....................................................................  38 General Kiln and Firing Practices.......................................................   38 Preparing and Loading Kilns..............................................................   39 Determining Appropriate Firing and Cooling Ramps. ................................................................................   41 . Kiln Firing Chart..................................................................................   43 7 Studio Safety........................................................................  44 Studio Safety Checklist.......................................................................   44 Toxic and Hazardous Materials..........................................................   45 Dust/Dirt Management......................................................................   45 Skin Care .............................................................................................   45 Equipment Safety................................................................................   46www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  3. 3. Preface This Ceramic Arts Handbook is an abridged version of Vince Pitelka’s best selling Clay: A Studio Handbook (The American Ceramic Society, 2001). His book has sold thousands of copies and is used both as a textbook and refer- ence resource in thousands of ceramics studios in art schools, community art centers, colleges, universities, and homes. While the book authoritatively explores each topic in great detail, we’ve extracted some of the basic essen- tials you need to get you started on your clay adventure. In his introduction, Vince writes “Through 30 years of experience as a studio potter, welder/fabricator/mechanic, and university educator, I have been collecting and disseminating information about ceramics. This book is a compilation of what I feel will be most valuable to ceramics students, studio artists, and educators, regardless of the particular direction of their ceramic work or teaching. I hope it will provide a convenient reference to help you through most of the steps in skill development, studio setup, and operations. It is my intent to offer answers and stimulate ideas.” Working in clay is one of the most rewarding activities. It’s suitable for all age groups and personalities and provides challenges for every skill level. We believe that this Handbook will provide you with a deeper understand- ing and appreciation of this medium, and hope that you’ll be able to spend many joyful hours ahead with your hands in clay. Bill Jones Ceramic Arts Book Manager Clay: A Studio Handbook by Vince Pitelka The American Ceramic Society, 2001www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  4. 4. Clay and Claybodies Chapter 1 The Nature of Clay We who work and play in clay have chosen well. Clay is among the most abundant and inexpensive materials on earth. The natural processes that weather and decay igneous rocks have been generous in providing us with extensive clay deposits in a variety of forms. Clay is abundantly available almost everywhere on earth, awaiting our need, often requiring little processing. Clay is a remarkable material for so many reasons. There is no other art or craft ­material that has the versatility and possibility of clay. We can cast it, throw it, extrude it, model it, roll it, pinch it, press it, slump it, stamp it, pull it, and push it. We can use it to create any form or shape, tiny or monumental, organic or rectilinear, thin and ­fragile, or thick and heavy. It is the most malleable and forgiving of art materials. It asks little of us, but with commitment and respect on our part, it rewards us generously. When subjected to a simple firing process, clay is transformed to hard, impermeable stone, and what was once so malleable and impermanent might now remain stable and unchanged for millennia. As if the mere workability and fired permanence of clay were not enough, we can also apply an unending variety of mineral coatings that fuse into glassy glaze surfaces of unlimited color and texture. When you place a lump of clay in anyone’s hand, the response is automatic. The hand closes and squeezes the clay, and a unique sculptural form is produced, subtly different from any other before. Few of us stop at that point, for the clay encourages us to apply different forces, responding to every push and pull. Until the clay begins to stiffen, there are no rules, and no externally imposed finality. We can undo what we have done, and we can immediately return any form or shape to a simple lump and begin anew. We do not know what we can do until we find out what we cannot do, and in order to fully discover the possibilities, we must take chances and experience lots of failure and mistakes. When in doubt, make something. Never allow frustration or failure to drive you from this medium. Do not ever stop experimenting and exploring. Do not be satisfied with a single direction in your work. Do not become smug with any aspect of the medium, no matter how well you think you know it. The clay will catch you off guard and will throw you for a loop every time. But as long as you maintain a spirit of discovery and curiosity, the clay will reward you frequently and generously.www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  5. 5. Clay and Claybodies • Chapter 1What Is Clay? and bisque strength, and yet it mini- Porcelain claybodies include Clay results from the natural mizes the water content and result- gritless high-fire bodies that firedecomposition of certain igneous ing shrinkage. close to pure white. Under cer-rocks—primarily granite and feld- tain circumstances, fired porce-spar. The end result of the decom- Claybodies lain can be translucent. True boneposition of granite and feldspar pro- Clay­bodies are mixtures of clay china (traditional translucent por-duces microscopic flat clay crystals and other materials designed to celain) is so-titled due to thecalled platelets. accomplish specific goals like addition of bone ash (calcium When microscopic clay platelets plasticity in throwing, stability in phosphate). Bone china bodies areare wet, they tend to stick together large-scale work, thermal shock very prone to warpage unless firedand slide smoothly against one resistance, dry and fired strength, on flat shelves with no hot spotsanother. The most plastic clays are or vitrification and density. in the firing. Actually, any reason-those with the smallest particle size. Earthenware claybodies remain ably well-fluxed cone 10 porcelain Different clays behave differently porous at low-fire, and yet at thrown very thin will give somedepending on the range and dis- higher temperatures will likely translucence without the disad-tribution of particle size and the deform and bloat before vitrifica- vantages of bone china.p­ resence of non-clay contaminants, tion. Traditional earthenware bod- Stoneware claybodies use naturalprimarily organic materials and ies are usually red or buff, a blend stoneware clay and/or fireclay asnonplastic minerals. of iron-rich surface clay plus sand a base, with additions of ball clay, or grog to give structure and often kao­lin, flint, fluxes, and/or grog orHow Does Particle Size with fireclay or stoneware clay to sand. Whiteness is rarely an issue,Affect Drying and Firing? increase firing temperature and so the materials are selected for The size and shape of clay par- reduce the chances of deformation desirable performance in form-ticles help determine plasticity, but and bloating. Modern low-fire ing and firing, regardless of color.they also have profound effects in bodies are often white, composed Natural stone­ware clays and plasticdry­­ing and firing the clay. The evap- of 50-50 ball clay and talc, and are fireclays with the addition of balloration of the water layer existing actually very similar to ones used clay produce an extremely plasticbe­tween each particle in the plastic by the Egyptians 5000 years ago. throwing body. Ad­ding sand orstate is what causes drying shrink- A low-temperature firing pro- grog gives tooth or structure in theage. The finer the particle size, the cess does not necessarily mean plastic state and reduces slumpingmore water layers are present, and an earthenware or whiteware during throwing or handbuilding,there­fore the greater the water con- clay—the raku and bonfire pro- allows thinner, taller wares withtent, and the greater the drying cesses often use highly refractory greater horizontal extension, andshrinkage. But at the same time, stoneware bodies that are simply reduces drying shrinkage. •the finer the particle size, the morecontact points between particles in underfired at low-fire tempera-the dry state, which gives greater tures and are therefore very porousdry strength in greenware and more and open, giving high thermalbonding surfaces in the early stages shock resistance. Low firing isof the firing. The ideal condition is especially appropriate for largeto have a mixture of sizes of clay par- sculptural work, as there is littleticles. This creates as much contact or no shrinkage in low firing, andsurface as possible between particles, common problems with crackinggiving good plasticity, dry strength, and warpage are minimized. www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  6. 6. Handbuilding Chapter 2 With handbuilding, the full scope of sculptural form and expression is available to the potter and the sculptor. It offers innumerable possibilities in structure and surface that are impossible or impractical on the wheel. With handbuilding processes, one can construct almost any imaginable shape. These processes are divided into three main categories: pinch, coil, and slab construction. Pinch and coil construction are the prevalent forming meth- ods in all ancient and tribal cultures. Slab construction was widely used in Meso-American pre-Columbian cultures, but otherwise is rarely found until modern times. Pinch construction is by far the simplest of these pro- cesses and provides the ideal introduction to all other ceramics construction methods. Pinch forms are usually confined to less than six inches in diam- eter, although there are exceptions to this. Pinch forms can be made either very thin and delicate or thick and substantial. There is something quite remarkable about an eggshell-thin pinched form, sanded and burnished, and blackware bonfired to a satin black luster. Coil constructed forms can take almost any shape imaginable. Coiling is the only method where novices can quickly learn to make very large ves- sels or sculpture, and the experience can rapidly increase their confidence in clayworking. Coiling is especially appropriate for organic forms, large volumetric vessels, and figurative sculpture. Clay slabs can be worked in either the soft-slab or stiff-slab method, indicating the condition of the slab while it is being worked. The soft- slab method is appropriate for slumped, draped, or soft-formed vessels, for clay masks, or for draping onto forms to make components to be stiffened and assembled. It is also ideal for making a wide variety of curvilinear and organic forms. The stiff slab technique is more appropriate for rectilinear and architectural forms, although the two approaches can be combined. Even for hard-edged geometric forms, many sculptors and vessel makers slump-mold curved components and assemble them leather-hard along with flat, stiff-slab components.www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  7. 7. Handbuilding • Chapter 2Wedging the Clay homogenizing any irregularities in Forming Method: Use the The wedging process is important composition or moisture content, method appropriate for the formsin all ceramic construction tech- and more importantly, eliminating you wish to make—for organicniques, as poorly wedged clay sim- air bubbles. Remember not to push shapes use coil, pinch, or soft slab,ply does not respond well. Wedging down from above, flattening the for geometric shapes use coil ormixes and homogenizes the clay and lump, and be sure not to push so stiff slab.eliminates air bubbles. Do not ever hard on each stroke that you smear Awareness of Surface Effects:settle for clay that is too wet or too the ball out too flat, because when With an appropriate forming methoddry—it simply isn’t worth it. With you stand it up and push again it and sensitivity to the surface createdclay that is too wet it is a simple will fold over on itself, trapping air during initial con­struction, subse-matter to wedge it on a dry plaster instead of eliminating it. Each push quent surface finishing may not beslab, or to slice it, stand the slices should just smear the bottom of the necessary. The forming or assemblyvertically and allow them to stiffen lump over a little, without ever trap- process itself can often create patternsup. Any clay that is too dry can be ping more air in the clay. or marks that are very pleasing.sliced, wetted down, and left in a Generally a minute or so of wedg- Concentration of Pressurebag or barrel overnight to absorb ing is enough, but, if you are blend- Points: All stages of manipulatingthe moisture. If you stiffen or soften ing different clays or working dry the clay depend on concentrationyour clay by these methods, be sure material into overly wet clay, it may of pressure points, giving you muchto wedge it very thoroughly before take considerably more wedging. If greater control than with a broadusing it. the clay lump begins to elongate to application of pressure over a large When first learning to wedge, either side, slap your palms against it area. EVERY part of your hand iscylinder wedging is usually the easi- to narrow it. useful. Remember that for everyest approach to master. Start with a action there is a reaction. Keep inball of clay that you can comfortably Handbuilding: mind the consequences of everystretch your fingers around (like a General Guidelines type of pressure that you apply tolarge orange). Set the ball on a flat and Suggestions the clay.surface, preferably a canvas-covered The following guidelines and sug- Wall Thickness: Make pieces onlytable. Hold both hands as you would gestions apply to all clayworking, as thick as is necessary. Extra thick-to shake hands with someone, and but especially to handbuilding. If ness does not necessarily increasegrab the ball firmly with your hands you familiarize yourself thoroughly structural integrity. In tall pieces youwrapped around either side, as indi- with these guidelines, the learning may wish to make the lower wallscated in Fig. 2.1. Applying pressure curve will be accelerated. slightly thicker, but otherwise main-downwards against the table, push Commanding Approach: Clay tain uniform thickness. For mostthe ball away from you slightly, mov- appreciates a vigorous, command- sculpture and vessels, even a verying it two or three inches so that the ing approach with an economy of large piece should not be more thanbottom smears forcibly against the motion. Whatever you do, do it for I to 1 thick anywhere.table. Roll the ball back up towards a specific reason. With an aggres- Base Support and Bottom:you (standing it up on the smeared sive, adventurous approach, you will Always construct large forms on a“extension”), grab again on either learn much faster than with a weak, sturdy movable board, with severalside as before, and push down and tentative approach. layers of newspaper under the clayaway as before. Repeat this at least Clay Consistency: Always start to prevent sticking and to allow for20 times for each lump of clay. with well-wedged clay of an appro- contraction of the piece during dry-This process creates a spiral twist- priate stiffness or softness for the ing shrinkage. On coil or slab work,ing and stretching within the lump, desired project. always build on top of a bottom slab www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  8. 8. Handbuilding • Chapter 2 of clay. Whenever possible, haveFigure 2.1 Cylinder Wedging a single continuous base that supports all parts of a piece. For example, if you are building an animal form with delicate legs, incorporate a base as part of the piece, thereby supporting and protecting the legs. Closed Spaces: Never create completely closed spaces, as they will trap steam pressure and may explode in the kiln. Always make breather holes. Tiny pinholes are adequate, but make several in casePlace hands on either side of the lump in Lean into the lump. one becomes clogged. Wheneverhandshaking position. possible, ALWAYS leave larger breather holes. Never apply addi- tions or appliques in such a way that air is trapped beneath them. Joining: Always join clay aggressively and firmly in a way that is appropriate for the con- sistency of the clay. NEVER press clay straight together with- out proper preparation, as this will result in the alignment of particles in a fracture plane. Soft clay may be joined with-Continue leaning into the lump, smear- Roll the top of the lump directly uping the lower portion against the wedg- towards you and grasp the sides. out scoring or slurry, especiallying table. in coil construction, as long as the pieces are smeared thor- oughly together, blending the seams inside and out to ensure thorough interlocking of the particles. In all other circum- stances, when joining parts or adding soft clay or appliques to a surface, score thoroughly with a fork or toothed rib, be sure to use enough slurry to force out all air bubbles, and press the parts in place firmly to eject allLean into the lump again, roll it back C ontinue until the lump is well blended excess slurry. With leather-hardtowards you, and repeat. and shows this appearance. clay, always fit the pieces well, www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  9. 9. Handbuilding • Chapter 2score thoroughly, use a generous metal tool, the surface feels scratchy, the clay’s ability to support itself.amount of slurry, and immediately and the displaced material falls away With large pieces, cover the surfacesjoin the pieces with firm pressure. freely as small particles. Many peo- where more parts are to be joined,In joining component parts or slabs, ple like to carve the clay at this and allow the rest of the piece towhenever possible score the inside stage, although a point between stiffen before continuing (or accel-of the joint and press in a small coil medium and hard leather-hard is erate stiffening with a hair dryer orof soft clay along the seam. Ideally, usually more desirable. This stage is propane torch).pieces to be joined together should appropriate for thin surface paint- Structure: At all stages, considerbe the same consistency and stiffness. ing, but not for thick slip techniques the structural integrity of the clayHowever, this is not always possible, like slip-trailing. Once the clay has (in both wet and dry stages) and itsand when joining pieces of dissimilar begun to bleach (lighten in color ability to support the upper por-moisture content, cover the assem- from drying) it has passed beyond tions of the piece. With large sculp-bled form and allow the moisture the leather-hard stages. tural forms, cross brace the interior.content to equalize before allowing Assembly: Regardless of forming Always support horizontal protru-the form to dry. Do not attempt to method, it is often advantageous sions or extensions with a tempo-join pieces that have dried beyond to build large pieces in sections to rary prop until they are firm enoughmedium leather-hard, except when be joined when soft or medium to support themselves. Do not over-using paper clay techniques. leather-hard or to be fired separately. look the possibility of using waddedStages of Leather-Hard: After the fire, they may be stacked newspaper as an interior support to Soft leather-hard is the stage loose, assembled on an armature, or maintain the shape of closed formswhere you can easily pick up a small cemented together with epoxy or or to support relief forms such asor medium-size piece without dis- silicone adhesive. masks. It may be left in place andtorting it, but the surface is still a bit Avoid Using Water: Do not use will burn away in the firing.tacky. When trimmed with a trim- water to smooth or finish a piece as Controlled Drying: Always care-ming tool, the trimmings tend to you work on it—it will just soften fully control the rate and degreeball up and stick under the tool, and the clay, removing structural integ- of drying. When time constraintsthe form is easily distorted or dam- rity and making it harder to work. demand it, large pieces may be stiff-aged. This is an ideal stage for joining Do not use water in place of slurry ened with a heat gun, hair dryer,parts, as long as they can be handled when joining pieces, except perhaps or propane torch before continu-without serious damage. with very soft clay. Other­wise, it ing with construction, but this can Medium leather-hard is the stage may just lubricate the clay surface result in uneven stresses on the clay.when all surface tackiness is gone, and encourage the formation of When necessary during construc-and plastic clay will not stick easily fracture planes. You may, of course, tion, pieces may be moistened withwhen pressed against the clay. When use water (applied with a sponge, a spray bottle to retard drying. Anythe surface is incised with a model- brush, or spray bottle) to slow down large pieces to be left covered withing tool, the displaced clay rises in the drying process when­ever it is plastic should first be draped withattached ridges along the groove. proceeding too ­rapidly. a large cloth (old towels or bedWhen trimmed, the trimmings fall Working in Stages: Each part sheet) to absorb and dissipate mois-freely away, and will not stick to the of the process should be done at ture. Otherwise, condensation undersurface or the trimming tool. the appropriate stage of softness or the plastic can run back onto the Hard leather-hard is the stage hardness. When constructing large piece in concentrated areas, possiblywhere the color is still “damp,” but shapes consider the clay’s ability causing collapse. Large complicatedthe clay is too stiff for easy trimming. to support higher sections. Do not pieces should be kept covered andWhen incised with a wooden or attempt to keep working beyond allowed to dry very slowly. Small www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  10. 10. Handbuilding • Chapter 2parts that protrude from a form thick­ness and the strength and resil- and thinning only the clay in themust be protected from quick dry- iency of the clay. Through pinch- lower portion of the pot, withouting, especially if they attach in two ing, we become extremely sensitive expanding the opening and theor more separate places. The easiest to the use of touch rather than upper rim.solution to this problem is to coat sight in determining and control- When you have made one passthose parts with wax resist. This will ling ceramic form. With practice, around the bottom, or when thecause the moisture to wick into the pinch construction can become area you are pinching has reachedbody of the piece, so that everything a viable method of creating small a suitable thickness (no more thandries at the same rate. In general, be vessels very quickly without the G), begin moving up the wall,sure to complete each part of the imposed mechanical precision of pinching in a very gradual spiral,process at the appropriate stage of the potter’s wheel. thinning the wall as you go. Thedryness. Do not attempt to bring a As you work through these outside surface may develop shallowpiece that is too dry back to a work- instructions, refer to the accom- surface cracks, but these are not aable moisture content. panying series of images in Fig. problem as long as the clay doesn’t Finish the Bottom: This is one 2.2.To begin, wedge a softball-size get too dry while you are still work-of the most frequently neglected lump of clay thoroughly. Divide ing it. You can smooth these cracksareas in ceramics. Whether a non- the clay into 2-diameter balls, and with your fingernail or a rib, but, iffunctional sculptural form or a loosely wrap all but one in plas- left, these shallow cracks can formfunctional vessel, a sloppily fin- tic to protect from drying. Place a very attractive surface texture notished bottom or lower edge can a ball in your cupped hand and unlike aged leather. Deep cracksruin the appearance and feel of with the thumb of that hand, begin are another story, especially if theyotherwise good work. In general, penetrating the center of the ball. are forming in the rim. As you area sharp edge is a mistake, as the With a rhythmic series of motions, expanding the pot and workingform seems to blend into or grow alternate between pressing your your way up the walls, if the sur-out of the surface on which it sits. thumb into the clay and rotating f ­ace begins to crack badly or if theUnless this is your intention, cre- the ball around your thumb with rim begins to crack at all, you mustate a slight undercut at the base the fingers of the other hand, keep- tend to it right away. Have a smallto create that all-important line of ing the ball resting in your cupped container of slurry handy, and atshadow that sets the piece off from hand the whole time. Keep this up the first indication of a bad surfacethe surface beneath. until you can feel the pressure of crack or a rim crack, put a very small your thumb through the bottom amount of slurry on the crack andMaking Pinch Forms of the ball, but stop before it actu- work it back together with your fin- No matter what one’s intended ally breaks through the surface. You ger or a modeling tool. Other­wisegoals or present skill level in ceram- have now established what will be do not use any water on the surfaceics, the pinch construction method is the center of the bottom of the pot. of the pot while it is underway, asan excellent exercise and an exciting At this point, instead of pressing water will soften the clay and inter-way to make small vessels. Whether straight down into the lump, begin fere with your progress.you are handbuilding or working on pressing the tip of your thumb to As you work your way up thethe wheel, the actions of the hand in the side to widen the bottom of the walls of the pot, the rim may inevi-squeezing and manipulating the clay pot, again alternating with rotating tably expand more than you want.and the relationship between the the pot (press, rotate, press, rotate, If this happens, cup your handinside and outside of the vessel are press, rotate, etc.). With your thumb over the rim and gently squeeze,of critical importance. Pinch con- bent, pressing only with the tip of rotate, squeeze, rotate until you havestruction teaches sensitivity to wall the thumb, you will be spreading reduced the rim to the desired www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society |
  11. 11. Handbuilding • Chapter 2Figure 2.2Pinch Construction a. egin pinch construction with a 2 B b. radling and rotating the lump C diameter ball of clay. in one hand, penetrate it with your thumb.c. otate continuously as you R d. top when your thumb pressure S e. inch to the side to begin P penetrate the lump. forms a dimple on the bottom. forming the walls.f. otate continuously, working up the walls. R g. inch to the final thickness and P h. ith a finger inside, smear the clay W resolve the surface. inwards to reduce the opening. www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 10
  12. 12. Handbuilding • Chapter 2diameter. Another good method for been the method known as coil and the personality of the makerreducing the rim diameter is to construction. This is still the stan- throughout its form. Altogether tooreverse the position of your fingers, dard method in all tribal pottery often, these qualities are erased onwith a finger on the inside under traditions, such as those currently wheel-thrown forms.the rim and your thumb on the active in Africa and the Americas. In general, a smooth-turningoutside smearing the clay inwards We must avoid any assumption that banding wheel offers tremendoustowards the center of the opening. coil construction is in any way advantages in most coil construc-Rotate the pot continuously as you inferior or primitive. The form and tion. If a kick wheel is available, it isdo this, and with practice you can surface of a coil pot is controlled by great to be able to rotate the formclose the rim to a very small open- the potter from start to finish with- with your feet while both hands areing, or even close it completely to out the influence of any mechani- busy adding coils and smearing themcreate an enclosed form. cal devices, and the expressive and together or in modifying the form. Finish the rim however you wish. imaginative possibilities are endless. Coil vessels are constructed by anSome pinch-potters like to leave a Even the most uniform and sym- additive process of building up thethicker rim, whereas others like to metrical coiled pot expresses the walls with long ropelike coils of claypinch the rim to a sharp edge. Some beautiful imperfection of humanity (or other repeating modules, suchpinchers like to keep a symmetrical,even pot and/or rim; others pre-fer an asymmetrical pot and/or anuneven rim. Each to his or her own. Figure 2.3 Rolling Coils for ConstructionIf you want to have an even, circularopening, let the pot get leather-hard, and then trim the rim. If youare going to sand the pot when dry,wait until then to resolve the shapeof the opening. When the pot is completed, youof course have numerous optionssuch as the application of tripodfeet, a pedestal base, small hanginglugs, handles, or other appendages. Ifyou wish to make spherical shapes,it is possible with a single lump, butyou also may wish to pinch twohemispheres and join them whenleather-hard. Pinch construction isonly practical for vessels up to fouror five inches in diameter, so theaddition of ornamental or func-tional elements can greatly increasethe visual impact.Coil Construction Throughout history the prevalenthandbuilding approach has always www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 11
  13. 13. Handbuilding • Chapter 2as small pancakes). Always start off the coil, bringing both hands back and press a single course of coils inwith a good supply of well-wedged to the center, moving then outwards place, working it well to force outclay—keep your clay supply cov- again, and repeating the process until excess slurry. As long as you areered with plastic so it doesn’t dry you achieve the desired length and using coils of soft clay, you need notout while you are working. This is diameter of coil. Do not attempt to score and slurry further as long ascritical, as the coils should be very roll coils with stiff clay. Use soft clay, you proceed with adding coils. Iftacky when joined. You must make and make sure the rolling surface you leave the form for a period ofthe choice of hand-rolled coils or, if is well dampened. If the coil starts time and the walls begin to stiffen atthe equipment is available, extruded to go oval, purposefully restore it all, then you should score and slurrycoils. You can roll long, uniform to round before continuing with before adding the next coil.coils very quickly by hand, without your rolling. With a little practice, When adding each successive coil,the mechanical precision and shape you will be able to roll uniform drape the coil from one hand so thatimposed by the extruder (Fig.2.3). coils of whatever size you wish as the coil end lays on the vessel wall on If you wish to make a ­ flat-bot- quickly as they can be produced with the far side of the form. With yourtomed form, select an appropriate an extruder. thumb on the inside and fingers onwooden board or bat and cover it For a small coil pot (8–12 diam- the outside, aggressively smear thewith several thicknesses of newspa- eter) the coils should be K to 1 in coil downwards on the inside withper. Make a flat slab of clay for the diameter, depending on how aggres- the thumb and upwards on the out-base—this need not be precisely sively you thin out the walls as you side with your fingers, as shown inrolled out—you can simply slap a join the coils. For a larger coil pot, Fig. 2.4e. Rotate the vessel (or movelump of clay between your hands the coils can be I to 1H or more around it) and slowly lower the coilor pound it out on a flat surface to in diameter. There are several con- onto the wall, smearing it in place asform a slab of an appropriate thick- siderations here. Once you become you go. Some coilers prefer to applyness for the intended form. Usually accustomed to coil construction, you single-level courses of coils one-by-it’s best to start with a slab larger will be able to anticipate how much one, whereas others tend to coil in athan the desired base and trim it you thin the coils during the join- continuous slow spiral. It will greatlyback after the lower portion of the ing process. Some tribal potters use help in this process if your coil potpot is complete. This also ensures coils that are several inches thick, but is sitting on a banding wheel orthat you always begin coiling the during the joining process the wall a kick-wheel. Tribal potters oftenwalls on top of the base, rather than is thinned to less than K. Also, once build their coil pots on the groundby laying the first coils next to it. the basic form is roughed out, you or on a low pedestal and walkThis will give a much stronger joint can come back and thin and form around the pot backwards as theybetween the slab base and the coiled it with the paddle-and-anvil or rib- add the coils and work the form. Ifwalls (Fig. 2.5). and-hand methods described below. you want the form to expand in size A very thick cylindrical coil form as the walls rise, you can reverse theCoiling the Walls may be thinned and shaped to a broad smearing movements, smearing up Roll out (or extrude) a supply of volumetric jar. It is essential that you on the inside and down on the out-coils. For the best coils, roll them anticipate these things in determining side on the side closest to you. Withon a well-moistened porous or the size of coils to be used. practice you can cause the diametercanvas-covered table. When rolling Don’t roll out too many coils to increase or decrease at will bycoils, spread your fingers apart (see ahead of time, because if they stiffen altering these movements. Do notFig. 2.4) and, as you roll forwards up at all they will not join satisfac- worry about cosmetic surface dur-and backwards, quickly move your torily. Score and slurry the desired ing this process. If you are smearinghands outwards towards the ends of attachment point on your base slab, aggressively, you will leave a rather www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 12
  14. 14. Handbuilding • Chapter 2Figure 2.4Coil Construction a. esuming coil construction on an in-prog- R b. Apply a coil and gently paddle in place. ress vessel: Score and slurry the edge.c. mear the soft coil downwards inside S d. s the next coil is lowered into place, A e. dd additional coils. A and out over the stiffened edge. smear it aggressively onto the previ- ous one.f. fter every three or four courses, A g. mear additional coils inwards to S h. o further close the rim T smear the coils together with diago- reduce the opening. opening, smear inwards nal strokes. with a rib. www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 13
  15. 15. Handbuilding • Chapter 2ragged surface appearance, but this Meso-American, and South­west convolutions and formed or assem-is evidence of well-joined coils. It is Native American cultures all feature bled immediately. With the stiff-slaba simple matter to stop periodically extraordinary design and technique method, the slabs are allowed to dryand smear the surface smooth with in coil construction. to leather-hard and are then cut toyour fingers or a rib. size and joined together. Be careful when increasing or Closing the Mouthdecreasing the diameter of your coil of a Coil Form Rolled Slabs andform to any radical degree, because When you wish to narrow the “Memory”the clay must have the structural neck or mouth of a coil vessel you When clay is formed by applica-integrity to support itself. Any time can simply apply the coils to the tion of pressure, the clay mass isa clay wall veers away from the verti- inner surface of the rim and smear compressed and the platelets arecal, gravity will make it tend to lean inwards on the outside of the vessel. pushed around in currents, depend-or collapse. If you are contemplat- As a refinement of this, support the ing on the type and direction ofing a radical expansion or reduction inside of the rim with your fingers pressure applied. The clay retains ain diameter, you must either allow and smear inwards over the top sur- memory of the compression and thethe clay to harden sufficiently as face of the rim with a rib, rotating currents, and it will shrink accord-you proceed, or you must provide a the form continuously. As long as ingly during the drying and firing.physical support for the clay. there is sufficient thickness in the This is true with all forming meth- If you leave your vessel for any rim, you can close the opening as ods, but it is rarely a problem. In slabtime, always cover the top coil with much as you want by this method. If construction, however, it must bedamp paper towels to keep it moist the rim is not thick enough to allow taken seriously. When rolling slabsand wrap the whole pot in plastic. this, stop and add another coil, and with a slabroller or rolling pin, if youWhen you resume work, if the then proceed with this method. roll only in one direction, you aretop coil has stiffened at all, always setting up a grain structure similar toscore and slurry before proceeding, Slab Construction a wooden board. Both a board andand paddle the first coil in place to Of the primary ceramic form- a unidirectionally rolled slab haveensure a good joint (see Fig. 2.4b). ing techniques, slab construction is greater strength along the lengthIf there seems to be a lot of con- the most modern. The technique than across the width, but will shrinkdensation inside the plastic in your of constructing with clay slabs is more across the width than alongstudio environment, drape a cloth or suitable for a wide variety of forms the length. If you assemble a largesheets of newspaper over the form and is the ideal method for achiev- slab form from these slabs, with thebefore covering it with plastic. This ing flat-sided geometric and archi- grain structures intersecting at angles,diffuses any moisture, which evapo- tectural forms. Historically, such the piece will likely pull itself apartrates and recondenses where the forms were generally built by the because of differential shrinkage inplastic touches the form. Without coil method, and except for the the drying and/or firing, especiallythis precaution, the condensation remarkable ­ slab-constructions of with high-­shrinkage claybodies, andcan concentrate and cause the clay pre-Columbian Meso-America, in high-fired work. This is the mostform to collapse. there is little evidence worldwide common problem area in slab con- The possibilities of coil construc- of slab con­struction before the struction. There are several solu-tion are unlimited, so almost any twentieth century. tions. If your slab­roller has a wideobject or form can serve as inspira- There are two primary kinds of enough bed, initially roll the slabtion. The ancient and tribal tradi- slab construction.With soft-slab con- thicker than you want, turn the slabtions of East Asian, Middle Eastern, struction, the slabs are manipulated 90 degrees, reset for a thinner rollerMediterranean, African, Peruvian, while still soft to form curves and height, and roll the slab again. With www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 14
  16. 16. Handbuilding • Chapter 2hand-rolled slabs, simply change the laying across the table pointing away degrees, and reroll until you get therolling direction frequently. In either from you, with the clay between the size, shape, and thickness you want.case, this will equalize the compres- two slats, and with the ends of the For greatest accuracy, measure thesion and currents, minimizing subse- rolling pin resting on the two slats, thickness in several places with aquent problems. you can roll slabs to an exact thick- needle tool, just as you would mea- All slabs are subject to this ness. However, with practice you sure the bottom of a pot.p­ roblem, whether you are mak- can roll slabs very uniformly with-ing slumped dinnerware, geometric out using the slats, and you are then Soft-Slab Constructionboxes, or tiles. In all cases, memory able to make use of the full width Soft-slab construction is the pre-of improper rolling can ruin the of the rolling pin. In either case, be ferred method for a wide variety offinished product. sure to turn the slab 90 degrees sev- vessel and sculptural approaches. It is eral times while rolling to equalize ideal for any form that may be cre-Rolling Out Slabs the compression. ated by wrapping or draping slabs on Commercial slabrollers are a Pound your clay into a rough slab, slump or drape molds, or by simplywonderful innovation, and if your place it on an appropriate sheet of manipulating a soft slab by hand. Thework calls for quantities of large canvas (depending on the size you following is a range of very simpleuniform slabs, you should consider want) on a sturdy table, and start projects that will serve as a goodthis major investment. If you do not rolling it, changing directions fre- introduction to soft-slab construc-have a commercial slabroller at your quently.Very soon the clay will stick tion and should provide a foundationdisposal you can easily roll out your to the canvas and won’t expand any for more ambitious soft-slab work.slabs by hand with a rolling pin. As more. Lay another sheet of canvaslong as you don’t need really huge on top, grab both sheets and the Soft-Slab Cylindersslabs, this is not a disadvantage, as slab, using the broad surface of your A wide variety of cylindrical orwith practice you will be able to fingers to minimize distortion of cone-shaped vessels may be maderoll out slabs by hand almost as the slab, and flip the whole work free-form out of soft slabs. Cups orfast and just as uniform as with a over. Pull off the top (formerly bot- mugs provide an excellent soft-slabslab­roller. Even if you are using a tom) sheet, pull the wrinkles out of project, and for these you should useslab­roller, keep in mind also that the the bottom sheet, turn the slab 90 slabs no more than G thick. Cut aroller tends to stretch slabs only in degrees, and roll some more. Roll strip of slab as wide as the desiredthe direction of travel. In order to out from the center, and minimize height of the cup and as long as theavoid irregular shrinkage or serious pressure as you approach the outer desired circumference. Score andwarping, these slabs should really edges, because it is very easy to get slurry the ends of the strip and joinbe aggressively hand-rolled on both the slab very thin at this point. Roll them together to form a cylinder.sides at 90 degrees to the original along the edges as well, but when You can either butt-join them (enddirection of travel. doing so, apply much more pressure to end) or you can overlap the ends. against the end of the roller that is Set the cylinder on a flat piece ofRolling Slabs by Hand on the slab than that hanging over slab and, with your needle tool, Using an extra-long rolling pin the edge. With practice, you will mark lightly around the bottomwith bearing-mounted handles, you find that by rolling outwards from circumference. Remove the cylin-can quickly roll out very large uni- the center and along the edges in der and score and slurry inside thisform slabs. If you need absolutely specific directions, you will be able circle, then press the cylinder gentlyuniform thickness, make a series of to control the way the slab expands into place. Cut away the excess basepairs of long wooden slats in gradu- and thus control the finished shape. slab, turn the cup over, and gentlyated thicknesses. With a set of slats Continue to flip the slab, turn it 90 tap the bottom slab around the www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 15
  17. 17. Handbuilding • Chapter 2edges to join it more firmly to the This is an excellent technique to molds made from plywood or foamcylinder. Finish the cup however use if consistency and uniformity of insulating board have become veryyou wish. An alternate approach is size and shape are desired, because popular. When these are set on ato use bisque stamps or a sheet of all the vessels made from one mold flat table surface, clay slabs may betextured material to create a pattern can be very similar in size and shape. slumped into these forms to createor texture in the flat slab before Professional potters make their flat-­bottom plates and trays. Similarly,making it into a cup. molds out of plaster, bisque-fired simple hump forms of plaster, wood, If you want uniform, evenly clay, plywood, or foam insulating or foam board provide excellentmatching cups, you may wish to board, but almost anything of the hump molds, and when slabs areform your cups around a removable desired shape will work as a mold. slumped facedown over such molds,core such as an empty soda can. Cut See Figs. 2.5 and 2.6. the edge may be trimmed and a foota strip of G-thick slab and wrap it You can make bowls and plates ring added immediately, minimizingaround the soda can to determine by simply slumping slabs inside an later finishing.the length of strip needed, then lay existing bowl or plate. Whenever For improvised slump-molds, shal-the strip back down on the table and the “mold” is a nonporous material, low forms work best, where a singlecut it to length. Wrap an appropriate be sure to use several layers of news- slab can usually be gently pressedwidth and length of dry newspaper paper strips beneath the slumped or into place. If you use a deep bowlaround the can (or other cylindrical draped clay to keep it from stick- as a mold you will have to apply theform). Don’t try to do this without ing to the mold. With slump molds slab in several pieces, scoring, slur-the layer of dry newspaper, as you made of plaster, bisque-fired clay, rying, and vigorously connectingwill be unable to slide the form out plywood, or foam board, no news- the joints. After the bowl stiffens upof the cylinder. Score and slurry paper layer is required. Open-center a bit, invert it on a board, removethe ends of the slab-strip, wrap itaround the newspaper-covered can,and join the ends together. Whilethe clay strip is still wrapped aroundthe can, if you wish you may press Figure 2.5 Foam Slump Moldsbisque stamps or textured materi-als into the surface for decoration. After you have joined the ends ofthe slab strip and added any addi-tional stamped decoration, hold thecylinder carefully cradled in onehand, push out the can, and removethe newspaper. Proceed with addingthe bottom as explained above.Slump-Molds In the current world of functionaland decorative ceramics, slump- ordrape-molded bowls and platters a. sing a foam slump mold: Drape U b. ently drop the mold repeatedly Ghave become extremely popular. to settle the slab into the mold. a slab over the mold.This method simply involves slump-ing a soft slab inside or over a mold. www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 16
  18. 18. Handbuilding • Chapter 2the mold or form, and use a wooden the added advantage of allowing you to the subject. There are a number ofrib or modeling tool to smear together to add a raised foot-ring to the base if ways to make tiles. The simplest is toany wrinkles or gaps on the outside you wish. However, if you try to slump roll out uniform slabs with a slabrollersurface. Or, as a decorative option, a deep-dished form on the outside sur- or by using a large rolling pin withmake sure to smear the inside connec- face of a rigid mold, you must remove a set of wooden slats as previouslytions very well and leave the outside it while still very damp, as any drying described. Let the slab stiffen to softseams visible. shrinkage could cause it to crack. leather-hard, and then carefully cut As mentioned, you can slump inside your tiles using a razor knife and aor outside of a mold or form. If you Making Tiles straightedge, taking into consider-slump a very shallow platter or bowl There are some excellent books on ation drying and firing shrinkage.over a convex form, you may be able the market about tile making, and this Be sure to consult the section onto allow it to dry in place, and this has will be only a very short introduction “Rolled Slabs and Memory.” If you Figure 2.10 Foam Hump Molds a. sing a foam hump mold: Place U b. ently drop the board repeatedly G the mold on a board and drape to settle the slab over the mold. the slab over it. c. core and slurry the back to accept S d. lace a coiled foot ring and gently P e. lean off excess slurry with a C a foot ring. paddle it level. damp sponge. www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 17
  19. 19. Handbuilding • Chapter 2make tiles from improperly made slabs, then this method will not work. Inthe clay memory will cause them to this case, the best solution is to simplywarp during drying and/or firing. make sure that the tiles are mobile Some production tile makers extrude (they are not stuck to the surface) andtheir tiles from a pugmill, using a spe- ensure that they dry slowly and evenlycial extrusion die with a thin horizontal under plastic or in a controlled humid-opening, producing a long continuous ity environment like a damp/dry box.ribbon of clay that can be cut to any Whatever method you use for mak-desired length. For small quantities of ing tiles, if your intention is to glazetiles, a similar extrusion die on a stan- them, all your efforts will be wasteddard clay extruder works quite well. unless you use a glaze that is a perfect Drying tiles is always a challenge, in match to the claybody. This is espe-order to produce perfectly flat tiles. cially true in high-fired tiles, where theOne good approach is to sandwich the clay becomes very pyroplastic. If thetiles between 24 squares of 1⁄ 2 dry- firing shrinkage of the glaze is greaterwall (sheetrock) until completely dry. than the clay, the tile will becomeFor economical use of space, you can concave during the glaze firing. If thestack up to six layers of drywall and firing shrinkage of the glaze is less thantiles. Obviously, this method works the clay, the tile will become convex.only for tiles that are of absolutely You can do simple tests ahead of timeuniform thickness, are completely to determine which glazes are appro-flat, or have only shallow incised or priate for your tiles. When necessary,impressed decoration. you can adjust the formula of a glaze If the upper surface of the tile is not to correct thermal expansion and makeflat, or if the thicknesses are irregular, it fit your claybody. •www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 18
  20. 20. Throwing Chapter 3 Of the various ceramic construction methods, throwing on the potter’s wheel is the most common in Western, European-based culture. For producing large quantities of individually handmade functional wares it is the most efficient method. A traditional approach to throwing involves completion of the pot upon the wheel so that very little needs to be done afterwards to finish the form.This is especially true of certain jar, vase, bottle, and bowl forms. Even if a trimmed foot or a knob is needed, we often use the wheel for those tasks as well. It is a joy to use the wheel in this way, but consider also that the wheel is an extremely versatile tool for making com- ponent parts to be assembled off-wheel into vessels or sculpture. The wheel excels for making hemispheres, spheres, ovoids, flat disks, cylinders, cones, tubes, and myriad other shapes. All of these components can be assembled in an unlimited number of ways. If you do not explore these possibilities, you are missing one of the best things that the wheel can do. Critical Points in Throwing The following review is designed to help beginning clayworkers become familiar with the most important points in throwing. There are lots of steps to keep track of, and it will help greatly to go over this list frequently and commit it to memory. Prepare Clay Properly. Wedge the clay thoroughly before using. This is especially important for wheel-thrown work. Don’t waste time on clay that is too wet or too dry. If clay is too wet, let it sit out until stiffened adequately and rewedge, or wedge it on a dry plaster surface, or wedge in some dry material (although this decreases plasticity). Don’t try to reuse clay from a previous pot that didn’t work out—let it stiffen up and rewedge it before using again. Prepare Plenty of Clay. With only one or two balls of clay in reserve, it is easy to develop an attitude of preciousness about each pot and a despera- tion to make each one work. Always prepare at least a dozen balls, and if a pot is not working, remove it immediately and start another one.www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 19
  21. 21. Throwing • Chapter 3 Clean and Dampen the for any shaping task. If you want and finishing small vessels. Use slowWheelhead. The ideal surface for to smooth or flatten a broad area, speed for large vessels.receiving the clay is slightly damp use a rib. Action→Reaction. For everybut not wet. Use a rubber rib to Centering: Full Body Con­ action there is a reaction. Keep insqueegee off all remaining slurry trol. Centering and wheel wedg- mind the consequences of everyfrom the previous pot, and if any ing depend on full body control. type of pressure that you apply tosurface moisture remains, remove it The work is not done by your arm the clay, and, when lifting or shap-with an old towel (Fig. 3.1). muscles, but rather by the full force ing a vessel, apply corresponding Slap Center. Before applying of your upper torso when you roll pressure both inside and outside thewater, slap center a ball of prop- your hips forward on the chair or form. Avoid expanding the diametererly prepared clay on the wheel- bench (Fig. 3.3). of a form without pressure fromhead or bat, and seal down the Work on the Right-Hand both sides, unless you are very sureedges thoroughly (Fig. 3.2). Side of the Wheel. After center- of the anticipated outcome. Avoid Touching the Clay ing, always work at the right-hand Lubrication. While throwing,When the Wheel Isn’t Turning. side of the wheel where the clay keep the clay lubricated adequatelyExcept for slap centering, always is moving away from your hands at all times. Excess friction is yourstart the wheel before applying (assuming you are throwing counter­ enemy. But remember that water ispressure, and always remove pressure clockwise). continuously absorbed into the clay,before stopping the wheel. Work at the Correct Speed. decreasing structural stability. As you Aggressive Commanding Use full speed for centering, wheel practice throwing, try to work fast.Approach. Clay appreciates a wedging, and penetrating the lump Remove Excess Water. Removevigorous commanding approach of clay. Use medium speed for wid- excess water whenever possible andwith an economy of motion. Be ening the bottom, lifting the walls, as soon as possible. If you workclear about the specific reason forwhat- ever you do, and rememberthat with an aggressive, adventur-ous approach you will learn very Figure 3.1 Throwing Positionquickly. Take risks. Concentration of PressurePoints. All stages of manipulatingthe clay depend on concentrationof pressure points. Concentratingforce on a small area of the claywill give much greater controlthan broad application of pres-sure over a large area. Centeringprimarily involves pressure withthe base of the right hand. Liftingthe walls involves pressure withslightly bent fingertips rather thanthe flats of the fingers or the hand.Once the clay has taken the formof a basic vessel, you should never Proper seating position when throwing.use the broad surface of your hand www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 20
  22. 22. Throwing • Chapter 3slowly and a piece begins to soften, inwards before cutting the pot off in throwing is to keep the outsideyou may remove excess water and the wheel. When cutting off pots, profile and inside profile as similar asslurry with sponges and ribs. When hold the cutoff wire very taut. possible. In other words, if the wallsyou reach an approximation of the When cutting off large flat shapes, are of uniform thickness, then thedesired shape you may remove all always do so with the wheel turn- outside and inside will be very closeexcess water and do the final shap- ing to keep the cutoff wire from to the same contour, whereas if theing with fingers, damp sponges, climbing up into the base of the pot. lower wall is very thick, the outsidethrowing stick (jug finger), or rub- Trim or otherwise finish the bottom and inside will be very different inber, metal, or wooden ribs. carefully, and make sure that there shape. Start off with a series of six When Throwing, Use the is a line of shadow around the base, or eight small cylinders, workingBest Tool for the Job. Usually separating it from the surface upon up to about 4 or 5 in height. Trywe throw with our fingers, but which it sits. to achieve walls that are no morethat is not always the best choice. than K thick at the bottom and GWhen throwing porcelain, it often Skill Development just below the rim, with a smoothlyworks very well to throw with a with Cylinders tapering wall in between. The bot-sponge on one side and a rubber or One of the best ways to develop tom thickness is not so crucial, butmetal rib on the other, or even with your ability on the wheel is to throw remember that if you wish to trimtwo rubber or metal ribs, especially lots of cylinders (Fig. 3.4). As you the bottom it should be K to H orwhen making broad, voluminous complete each one, cut it in half more thick (this will give you ampleforms. When making a tall form vertically with your cut-off wire thickness for trimming a raised foot-with a narrow rim, it makes sense to to observe the cross-section pro- ring), and make sure that the bot-neck in the rim immediately upon file. Don’t try to do this with other tom is flat and level, with a distinctachieving the desired height, and shapes, because they will collapse as rounded corner where the bottomthen use a jug-finger to broaden the soon as you cut them, whereas half ends and the wall begins. Later youbody of the vessel. of a cylinder will still stand up. When may wish to throw forms with a Attention to Rims. When lift­ you view the cut cylinder there curved bottom, but for skill develop-ing walls, always stop just short of are several important things to look ment it really helps to become famil-the rim. Compress rim regularly, and for. First of all, a primary objective iar with flat-bottom cylinders.on cylinder-based forms keep rimdiameter smaller than base diameteruntil wall height is established. Synchronize Movements. Figure 3.2 Slap CenteringWhen lifting or wheel wedging,synchronize the movement of yourhands with the speed of the wheelso as not to leave deep spiral groovesor marks. Much of the problemsin learning to throw are caused bylifting too fast in proportion to thespeed of the wheel. Cutting off the Pot and Fin­ishing the Bottom. These can Seal the lump down with the lower edge of your hands while the wheel ismake or break an otherwise good turning slowly.pot. Always bevel the lower edge www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 21
  23. 23. Throwing • Chapter 3 When you cut each cylinder in mentioned earlier, centrifugal force not attempt to repair it. If there ishalf remember to carefully observe tends to force the clay outward from sufficient clay below the crack youthe uniformity of the walls, the the center, and in making bowls may cut away the damaged portionsmoothness and thickness of the you can take advantage of this force and proceed with what is left.bottom, and the uniformity and rather than having to counteract As a general rule, in the early stagethickness of the rim. There should it. When lifting the walls, simply of throwing any form it is wise tobe very little variation in thickness lift outward and allow the form avoid radical horizontal orientationof the walls from bottom to top, to expand. Be especially careful to of the clay. In other words, in lift-and the lower inside corner should compress the rim with every lift, ing and widening a bowl form dobe quite square, as indicated in Fig. because the rapid expansion of the not widen the bottom too much3.5g. With each successive cylinder, diameter can easily cause the rim to initially so that it hangs over thetry to respond to the problems or crack. If the rim does crack badly do foot. Instead, raise the walls so thatfaults in the previous ones, so thatyou are continuously experimentingand developing your technique. Figure 3.6 Throwing a Bowl If you find yourself frustrated withthe ordinary cylinder, try doingtimed cylinders. Sit down at thewheel with 20 or 30 small balls ofclay, and have someone time you.This is a great exercise to do in aclassroom situation. Start with five-minute cylinders, with 30 secondsin between to scrape off the previ-ous one and put a new ball of clayon the wheel. When time is called,immediately stop the cylinder youare working on and scrape it off the a. hrowing a bowl: Lift outwards. T b. ift repeatedly, maintaining Lwheel. After two or three of these, straight walls.reduce the time to four minutes,then three, two, and finally one-min-ute cylinders. You will be absolutelyamazed at the progress you can makethrough several of these sessions.Throwing Bowls Generally, most bowls are thrownon bats. In making bowls, penetratethe lump and widen the bottomjust as in forming cylindrical forms,but there is no need to undercutwhen widening to keep the opening c. rim away excess clay from base. T d. esolve shape with rib, fingers, or Rnarrow. This will result in a wider, sponge.lower doughnut-stage (Fig. 3.6). As www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 22
  24. 24. Throwing • Chapter 3Figure 3.3 Centeringa. entering and wheel wedging: C b. rofile of properly centered lump. P c. ontinue the side pressure while C Initially center the clay with firm hinging hands together, causing side pressure. clay to rise.d. ross section showing intermedi- C e. aise the lump to a rounded peak. R f. ross section showing maximum C ate stage of wheel-wedging. rise, with heel of thumb poised to press clay back down.g. ith continuing side pressure to W h. ontinue pressing downwards as C i. inalize centered form after F prevent mushrooming, press clay lump widens. repeated wheel-wedging. back down. www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 23
  25. 25. Throwing • Chapter 3Figure 3.4 Throwinga. asic throwing: After centering B b. enetrate the lump to create a P c. iden the bottom using the “claw” W and wheel-wedging, form a dim- V-shaped opening. motion, and compress the bottom. ple and apply water.d. egin lifting the walls. B e. aintain firm, even pressure and M f. top lifting just shy of the rim. S steady upwards movement.g. ompress the rim. C h. egin second lift, pressing into B i. ontinue lifting slowly and steadily C the clay at the base. up to the rim.j. epeat with the third lift. R k. egin shaping the vessel as you B l. hink about the shape as you fol- T lift. low through. www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 24
  26. 26. Throwing • Chapter 3Figure 3.5 Throwing Cross Sectionsa. ross sections of basic thrown C b. enetrating the centered lump. P c. idening the bottom. W form: Creating the dimple.d. he initial lift. T e. top just shy of the rim. S f. econd lift, pressing into the base. Sg. roper position during lifting, P h. inal lift. F i. esolving the shape. R with inside fingers slightly ahead of outside fingers. www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 25
  27. 27. Throwing • Chapter 3they are straight or slightly convex shape you desire. For small bowls the open, depending on tempera-(like the flare of a trumpet) rather it is generally best to finish the ture, humidity, and air movement. Ifthan concave (like a hemisphere), shape with your fingers, but for you won’t be able to get back to itand make sure that initially the larger bowls it usually works best until the next day or later, you mustwalls flare out at no more than a to use a sponge or a curved rib to cover it with plastic sheeting. The45º angle from the bottom. This is establish the inside profile. With best material to use for this is a dry-an extremely stable form that will the wheel rotating at low-medium cleaner bag or trash bag cut open toallow you to achieve the desired speed (medium for a small bowl, form a rectangular sheet. Wrap theheight, diameter, and wall thickness. low for a large one) work the fin- plastic under the edges of the bat Before proceeding further, always gers, sponge, or rib up from the or ware board to prevent air cur-trim away excess clay from the out- bottom of the bowl, curving the rents from drying the pot. In veryside base, (Fig. 3.7) because it will be clay outward a little with each pass dry weather, especially in the wintervery difficult to get access to this area from bottom to top. With your right when a forced-air heater is running,when the curvature of the bowl is hand, always follow the position of a pot may dry out in a day or twocomplete. If you are planning to trim the rib with gentle sponge or finger even when well wrapped. Checkthe bowl, then you need only trim pressure on the outside of the bowl. your pots frequently, and if they areaway excess clay and create a slight Repeat these passes until the bowl drying too much, spray them lightlyundercut to facilitate cutoff. If you takes the desired shape. When using with a household spray bottle filledare not planning to trim the bottom, a rib to shape a bowl be sure to with water. If you anticipate havingyou can undercut the edge with a incline it so that it slides smoothly to leave them for several days andwooden rib, applying gentle pressure over the clay rather than scraping or are concerned about excessive dry-with a sponge to the outside base, cutting into it. ing, you can drape dampened paperand create a very pleasing “foot.” towels or rags over your pots or sim- For small bowls you may use your Drying Your Pots ply place several wads of wet paperfingers, a sponge, or a curved rib to It is possible to throw some shapes towels on the ware board next to,bring the walls out to the desired so that they have a perfectly accept- but not touching, the pots and wrapcurvature. On large bowls it is a able base straight off the wheel, with them securely in plastic. Even ingood idea to remove all slurry and very little finish work (Fig. 3.7). In very dry weather, this should keepwater from the inside and outside most cases, however, you will need them at the leather-hard stage for atsurfaces before final shaping. You to trim the bottoms of your pots. least a week.can accomplish this with a sharp- After finishing the pots and plac- Pay very close attention to theedged rib, like the standard stain- ing them on ware boards you must drying process. It is much easierless steel kidney-shaped rib. You anticipate when you will be able to trim a pot or add handles withcan also squeeze all water out of to work on them next and pro- good results when you do it at thetwo sponges and, with the wheel tect them appropriately from exces- proper soft-to-medium leather-hardat slow-medium speed, use them to sive drying. All trimming, attaching stage. Checking pots frequently toremove water and slurry from the of handles, slip painting, appliquesurface. Either of these techniques work, and most decorative carvingwill in effect “wring” water out of must be completed at the leather-the clay, firming it up structurally so hard stage, when the clay is stiffit is less likely to distort or collapse enough to handle but still damp.as you proceed. Upon completing a pot, if you Final shaping can be done with a plan to trim it later that same dayvariety of tools, depending on the you may be able to leave it out in www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 26
  28. 28. Throwing • Chapter 3monitor drying is simply part of the forth, until the four lumps are equally surface and to the trimming tool. Ifprocess. If a pot dries beyond proper spaced around the pot. Maintain pres- the clay is too dry, it will feel verytrimming stage before you trim it, sure with your hand against the center hard and scratchy when trimming.don’t waste time on it—recycle it. of the pot throughout this process, Do not continue with trimming if so that it doesn’t shift on the wheel- the clay is too wet or too dry.Finishing the Bottoms head. For a low bowl, plate, or cup After the bottom is completely shape, very small lumps are adequate. level, begin trimming off all excessof Your Pots For taller mug and jar shapes, larger clay from the outer edges of the Place the pot upside down in the lumps will be necessary. The lumps base. If the lower walls are thickcenter of the clean wheelhead. Start should never be pressed hard against you may trim some clay off them,the wheel at slow speed, and hold the clay form, but they always must but try not to rely on this any moreone finger near the edge of the pot. be smeared down thoroughly against than necessary. As much as possible,Slowly move it in towards the pot the wheelhead. trim the excess clay off the loweruntil your finger touches the edge When selecting trimming tools, walls while the pot is still wet onof the pot once on each rotation. you will have the greatest control the wheel.This is the point where the pot with a very small trimming sur- When trimming a leather-hard pot,is farthest off center. On the next face. The corners of a square-ended remember that the objective is torotation when the pot touches your band-loop trimming tool give you make the outside profile (except forfinger, stop the wheel right at that the best option. Hold the handle of the foot ring) as much as possible likepoint. Move the pot slightly towards the tool in your right or left hand the inside profile, and trimming excessthe center of the wheel and repeat just as you would a pen or pencil, wall thickness is perfectly acceptable.the process until the pot seems on with the square end pointing down. Use the flat cutting edge to refinecenter. When you get good at this, Brace it firmly near the tip with the trimmed area and to blend it intoyou may wish to try the tap-center the fingers of your other hand and the untrimmed part of the wall. Usemethod, where you gauge whether with the cutting edge of one corner the curved end of a trimming tool tothe pot is on center as describedabove, but then, without stopping begin trimming the pot—remember trim any convex areas.the wheel, tap the form to move concentration of pressure points. If the bottom of the pot was quiteit further on center. Many profes- Bring the wheel up to medium thin to begin with, you may notsional potters use this method and speed, start at the center, and trim a be able to trim a raised foot ring,can center a pot almost instantly. If slow overlapping spiral all the way in which case the trimming pro-you are not accustomed to it, it may to the outer edge. If the bottom is at cess is finished at this point. If youseem all but impossible. all irregular in height, then you will really want to find out how good When the pot is centered, form need to take repeated passes to trim a job you’re doing, you may havefour small lumps of clay, each the size it down to level. Hold the tool very to sacrifice a few trimmed pots byof your thumb. While gently applying firmly close to the tip with both cutting or breaking them in half todownwards pressure against the center hands during this process to over- observe the cross-section profile ofof the bottom with one hand, press come any irregularity in the bottom. the trimmed bottom.one lump in place, gently nestling If the clay is the proper medium If there is enough thickness tothe lump against the pot and apply- leather-hard, then it will trim very trim a raised foot ring, after you haveing primary force to smear the lump easily and evenly, and the trimmings leveled the bottom and trimmed offdown against the wheelhead. Avoid can be easily brushed off the surface any excess clay from outer edgesapplying excessive pressure against the with a soft brush or with your fin- and lower walls, examine the profilepot. Rotate the wheel and pot 90º, gers. If the clay is too wet, the trim- of the pot and decide what kind ofpress another lump in place, and so mings will ball up and stick to the foot ring you want. In some cases www.ceramicartshandbook.com | Copyright © 2001, 2007 The American Ceramic Society | 27