Plaster of Paris (POP) is a white or yellowish powder made primarily of calcium sulfate hemihydrate, which hardens when mixed with water and is widely used in construction and decoration. Its historical usage dates back to ancient times, particularly in sculpting, with production involving gypsum heated at specific temperatures. While it offers advantages such as resistance to cracking and ease of application, it is not suitable for moist conditions and requires skilled labor for application.

2. Plaster of paris (pop)

3. Introduction
• Calcium is the fifth element and the
third most abundant metal in the
earth’s crust. The calcium compounds
account for 3.64% of the earth’s crust.
This element is essential for the life of
plants and animals, for it is present in
the animal’s skeleton, in tooth, in the
egg’s shell, in the coral and in many
soils. Seawater contains 0.15% of
calcium chloride.
• Calcium cannot be found alone in
nature. Calcium is found mostly as
limestone, gypsum and fluorite.
Stalagmites and stalactites contain
calcium carbonate.
Calcium
Calcium
Limestone
Gypsum
Fluorite

4. Introduction
Definition
• Plaster of paris appears as white or yellowish, finely divided, orodless
powder consisting mostly or entirely of calcium sulfate hemihydrate,
CaSO4*1/2H2O. Forms a paste when it is mixed with water that soon
hardens into a solid. Used in making casts, molds, and sculpture.
Generally non-toxic.

5. Introduction
History
• The term plaster of Paris was first used
in the 17th century due to large quarry
deposits of gypsum located in
Montmartre, a district of Paris. They
mostly use them for sculpturing,
decoration and surface for painting.
• But researcher has found plaster wall
and artifacts for interior of Great
Pyramids. This prove usage of plaster
has been since ancient times.
• Invention of plaster bandage can be
attributed to Arabicdoctor in 1000 C.E.
(Al-Tasrif). But POP bandageswere first
used by Matthysen, a Dutch military
surgeonin 1952.

6. Manufacture
• Plaster of Paris is prepared by heating calcium sulfate dihydrate,
or gypsum, to 120–180 °C (248–356 °F). With an additive to retard the set,
it is called wall, or hard wall, plaster, which can provide passive fire
protection for interior surfaces.
• For the production of Plaster of Paris, gypsum is the vital role material.
• The process of making Plaster of Paris includes motor, attribution disc,
rotary cylinder, drum calciner, reactor, dryer, boiler, thermometer, jar and
furnace.
• Firstly, the impurities from gypsum is removed by washing them. Then, it is
dried in direct sunlight. Further, using pulveriser gypsum is pulverized.
• Then gypsum powder is calcined in a rotary drum calcinatory using some
sort of fuel. Then the final product is ready.
Plaster of Paris making process

7. Manufacture
Plaster of Paris making process
Raw gypsum Washing down impurities Drying of gypsum in direct
sunlight
Pulverization of gypsum
Calcination of gypsum powder
Final product

8. Types
Types of Plaster of Paris
Plaster of
paris
Cement
plaster
Lime
plaster
Mud
plaster
Stucco
plaster

9. Types
Lime plaster
• When lime is used as the binding materials, it is called lime plaster.
• Lime plaster is type of plaster composed of hydrated lime, sand and water.
• Lime plaster is similar to Lime mortar, the main difference is the based on use
rather than composition.
• Mortar for lime plaster is usually prepared by mixing sand and lime in equal
proportions. Cement is small quantity added to the mixture to improve its strength.

10. Types
Cement plaster
• When cement is used as the binding materials, it is called cement plaster. It is
especially suited for damp condition.
• Cement plaster is usually applied in one coat.
• The thickness of coat can be 12mm, 15mm or 20mm depending upon the site
conditions and type of building. When the thickness of plaster is more than 15mm.
6 MM thickness of cement plaster and cement mortar 1:3 or 1:4 is recommended
for cement plastering on RCC surfaces.

11. Types
Mud plaster
• The surface to be plastered is prepared exactly in the same manner as that
for lime or cement plaster.
• Mud plaster is generally applied in two coats, the first coat being 18mm thick
while the thickness of the second coat is kept 6mm.

12. Stucco plaster
Types
• Stucco is the name given to a decorative type of plaster which gives an excellent
finish.
• Stucco plaster can be used for interior as well as exterior surfaces.
• It is usually laid in three coats making the total thickness of the plaster to about
25mm the first coat is called the scratch coat; the second a finer coat, also known
as the brown coat, and the third is called white coat or finishing coat.

13. Properties
Properties of good Plaster
• It should be hard and durable.
• It should be possible to apply it during all weather conditions.
• It should adhere to the background and should remain adhered during all
climatic changes.
• It should be cheap and economical.
• It should offer good insulation against sound and high resistance against fire.
• It should effectively check the penetration of moisture from the surfaces.

14. Characteristic
s Characteristics
• Plaster of Paris is easy to spread and level.
• It is fire resistant highly.
• It forms a thick surface to resist normal knocks after drying.
• It expands very slightly on the setting.
• It does not cause cracking of surfaces. It gives a decorative interior finish. It
mixes up easily with water.

15. Application
Methods of Application
• The plaster may be applied in one or more coats, but the thickness of a
single coat should not exceed 12 mm.
• In the case of inferior or cheaper type of construction, the plaster may
usually be one coat. For ordinary type of construction, the plaster is
usually applied in two coats, whereas for superior type of works it is
applied in three coats.
• The final setting coat should not be applied until the previous coat is
almost dry.
• The previous surface should be scratched or roughened before applying
the next coat of plaster.
• In plastering, the plaster mix is either applied by throwing it with great
force against the walls or by pressing it on the surface.

16. Application
Tools using for Application
1. GAUGING TROWEL :
• A gauging trowel is used for gauging small quantities of
materials and for applying mortar to mouldings, corners
etc.
• The end of the trowel blade may be either pointed or bull-
nosed.
2. Float :
• A float is used for applying and spreading mortar on the
surface.
• There are two types of float
a. Metal float
b. Wooden float

17. Application
Tools using for Application
a. Metal float :
• Metal float is made of thin tempered steel is known as
laying trowel.
• Laying trowel is used for laying the plaster material and
trowel ling so as to get desired finish.
• There are two types of plate in which stiff plate is used for
applying and trowel ling the plaster and thin plate is used
for finishing coat.
b. Wooden float :
• The wooden float is commonly known as skimming float is
used for the finishing coat of plaster.

18. Application
Tools using for Application
3. Floating rule :
• It is used for checking the level of the
plastered surface between successive
screeds.
4. Plumb bob :
• This tool is used in forming the screeds
perfectly in a vertical plane.

19. Application
Tools using for Application
5. Miscellaneous tools :
a. Spirit level
b. Scratchers
c. Set square
a. b.
c.

20. Finishings
Types of Finishing
1. Smooth cast :
• It is a finish which presents levelled
and smooth surface.
• The mortar for the finish is made by
mixing cement and fine sand in ratio
of 1:3.
2. Rough cast :
• It is a finish in which the mortar for the
final coat contains a proportion of
fairly big size coarse aggregates.
• The mortar for the finish is made by
mixing cement fine sand & coarse
aggregates in the ratio of 1: ½:3.

21. Finishings
Types of Finishing
3. Pebble dash :
• It is a finish in which small pebbles or
crushed stones of suitable size are thrown on
to a freshly applied final coat of mortar and
left exposed.
• Ratio:- cement: coarse sand = 1:3
4. Textured finish :
• In this finish, ornamental patterns or textured
surfaces are produced by working with
various tools on the freshly applied final coat.

22. Defects
Defects in plaster work
1. Cracking :
2. Efflorescence :
• It is solvable salt are present in
bricks or the mortar they absorb
moisture.
3. Falling out of plaster :
4. Blowing of plaster :

23. Prevention
Prevention methods
1. Cracking - Continuous damping of plaster, in order to slow down any rapid
drying, to prevent cracking from happening.
2. Blistering - Usually caused by uneven mixing of plaster, which could be
prevented by ensuring a sufficient mixing between cement and its
components to form plaster.
3. Falling out of plaster - Thermal variation could be minimized my the means
of water sprinkling method on the surface of the wall to reduce excessive
thermal differences. For the case of inadequate bonding, it can be prevented
by ensuring the plaster are plastic enough (workable) to stick into the wall.
Imperfect adhesion could be minimized by the act of good
workmanship/carpentership.
• Ensure to apply enough pressure to the plaster while plastering, to ensure the
plaster mortar goes into any deep irregular surface, and cover any holes as
much as possible.

24. ADV /
DISADV Advantages and disadvantages
Advantages Disadvantages
• It does not shrink while setting.
• Therefore, it does not develop cracks on
heating or setting.
• It forms a thick surface to resist normal
knocks after drying.
• It mixes up easily with water and is easy
to spread and level.
• It gives a firm surface on which the
colours can settle.
• It has no appreciable chemical action on
paint and does not cause alkali attack.
• Plaster of Paris gives a decorative interior
finish. Its gypsum content provides it a lot
of shine and smoothness.
• It can easily be moulded into any shape.
• Gypsum plaster is not suitable for exterior
finish as it is slightly soluble in water.
• It is more expensive than cement or
cement lime plaster.
• It cannot be used in moist situations.
• Skilled labour is required for precise
application and thus labour cost for
applying plaster of Paris is high.

25. Forms
Market forms of pop
Market form Information Image
1. Powder form
It is available in 1
kg/ ₹15, 3 kg/ ₹40
and 5 kg/ ₹70 of
packages.
2. Bandage form
It is available in 10
cm/ ₹65 and 15
cm/ ₹140 of
bandage rolls.