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Restoring the Lions' Roar: Documenting and Replicating Limestone Sculptures through Laser Scanning, 3D Modeling, & CNC Machining
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Restoring the Lions' Roar: Documenting and Replicating Limestone Sculptures through Laser Scanning, 3D Modeling, & CNC Machining

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The report is the written version of the presentation given at the 3D Digital Documentation Summit, at the Presidio of San Francisco, in San Francisco, CA on July 11, 2012.

The report is the written version of the presentation given at the 3D Digital Documentation Summit, at the Presidio of San Francisco, in San Francisco, CA on July 11, 2012.

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Restoring the Lions' Roar: Documenting and Replicating Limestone Sculptures through Laser Scanning, 3D Modeling, & CNC Machining Document Transcript

  • 1. KREILICK CONSERVATION, LLC ARCHITECTURE • SCULPTURE • OBJECTS RESTORING THE LIONS’ ROAR: D OCUMENTING AND R EPLICATING L IMESTONE S CULPTURES THROUGH L ASER S CANNING , 3D M ODELING , & CNC M ACHINING 3D D IGITAL D OCUMENTATION S UMMIT T HE P RESIDIO OF S AN F RANCISCO S AN F RANCISCO , CA J ULY 11, 2012 519 TOLL ROAD • ORELAND, PA 19075 • 215-572-6616 www.kreilickconservation.com
  • 2. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 RESTORING THE LIONS’ ROAR: DOCUMENTING AND REPLICATING LIMESTONE SCULPTURES THROUGH LASER SCANNING, 3D MODELING, & CNC MACHINING 3D DIGITAL DOCUMENTATION SUMMIT THE PRESIDIO OF SAN FRANCISCO SAN FRANCISCO, CA JULY 11, 2012 AUTHORS: CAITLIN SMITH, PROJECT CONSERVATOR, KREILICK CONSERVATION, LLC T. SCOTT KREILICK, PRESIDENT/CEO/PRINCIPAL CONSERVATOR, KREILICK CONSERVATION, LLC HARRY ABRAMSON, PROJECT MANAGER, DIRECT DIMENSIONS, INC. GLENN WOODBURN, TECHNICAL PROJECT MANAGER, DIRECT DIMENSIONS, INC. JON LASH, PRESIDENT/CEO, DIGITAL ATELIER, LLC ii
  • 3. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 TABLE OF CONTENTS Table of Contents ................................................................................................................ 1 List of Figures ..................................................................................................................... 2 Biographies ......................................................................................................................... 3 Key Issues, Topics, & Concepts ......................................................................................... 5 Introduction ......................................................................................................................... 5 The Lions ............................................................................................................................ 7 Restoration, Data Collection, and Replication.................................................................. 10 Laser Scanning .................................................................................................................. 11 CNC Machining ................................................................................................................ 15 Conclusions ....................................................................................................................... 17 1
  • 4. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 LIST OF FIGURES (All images are the property of Kreilick Conservation, LLC unless otherwise stated.)Figure 1: Karl Bitter (Karl Theodore Francis Bitter Papers, Archives of American Art, Smithsonian Institute) ............................................................................................................. 5Figure 2: Entrance to the First Prudential Building in Newark, New Jersey (Prudential).............. 6Figure 3: Prudential Lions in Branch Brook Park before treatment in Newark, New Jersey. ........ 7Figure 4: Prudential Lion exhibiting staining, biological growth, gypsum crusts, graffiti, mechanical damage, spalling, and erosion of details. ............................................................. 8Figure 5: Graffiti paint revealed after paint removal. ..................................................................... 9Figure 6: Graffiti and missing tail................................................................................................... 9Figure 7: Treatments (clockwise from top): paint removal, misting, poulticing, laser cleaning, & Dutchman. ............................................................................................................................. 10Figure 8: Sculptor making clay repairs. ........................................................................................ 12Figure 9: Clay repairs of lost details. ............................................................................................ 12Figure 10: Direct Dimensions laser scanning lion statue.............................................................. 13Figure 11: Direct Dimensions laser scanning lion statue.............................................................. 14Figure 12: Polygonal computer model created from laser scanning............................................. 14Figure 13: CNC machine at the Digital Atelier milling foam lions. ............................................. 15Figure 14: Foam model, after compiling pieces and before painting. .......................................... 16Figure 15: Metropoles mold making process. .............................................................................. 16Figure 16: South lion, Pat, before treatment. ................................................................................ 18Figure 17: South lion, Pat, precast concrete replica...................................................................... 18Figure 18: South lion, Pat, before treatment. ................................................................................ 19Figure 19: South lion, Pat, precast concrete replica...................................................................... 19Figure 20: Replicas in place in Branch Brook Park. ..................................................................... 19Figure 21: Original limestone lion after treatment. ...................................................................... 20Figure 22: South lion, Pat, precast concrete replica...................................................................... 20 2
  • 5. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012BIOGRAPHIESCaitlin Smith - Project ConservatorCaitlin Smith is an architectural and sculptural conservator for Kreilick Conservation, LLC. Shereceived a Master of Science in Historic Preservation from the University of Pennsylvania, andundergraduate degrees in Historic Preservation and Political Science from the University ofMary Washington. Her graduate thesis, Cleaning Methods for the Removal of Limewash fromPainted Plaster Surfaces: Utilizing Ion Exchange Resins on the Interior Architectural Finishes ofthe Capilla de Nuestra Señora del Rosario in Iglesia San José in San Juan, Puerto Rico, waspresented at the IIC 2010 Congress and the APT 2009 Conference. She has worked with theArchitectural Conservation Laboratory at the University of Pennsylvania, the Fairmount ParkHistoric Preservation Trust, the Jekyll Island Historic Preservation Internship Program, KenmoreMansion, and the US/ICOMOS International Exchange Program.T. Scott Kreilick - Principal Conservator & Project ManagerT. Scott Kreilick is President, CEO, and Principal Conservator of Kreilick Conservation, LLClocated in Oreland, PA. Scott is a Professional Associate of the American Institute forConservation of Historic and Artistic Works (AIC). Scott earned his MS in Historic Preservationwith a Specialization in Architectural Conservation from the University of Pennsylvania; and hisBA in the History and Sociology of Science, also from the University of Pennsylvania.Established in 1996, Kreilick Conservation, LLC provides condition assessments, laboratory andfield analysis of materials, emergency response and stabilization, treatment, documentation, andmaintenance of architecture, monuments, sculpture, and objects, with a specialization in metalsand stone.Harry Abramson - Project ManagerHarry graduated from James Madison University in 1989 with a Bachelor of Science Degree inEconomics. With a career in technical sales and project management along with a love andrespect for the arts, Harry joined Direct Dimensions in 2004 to develop technical solutionsserving the art industry. Harry’s work has helped countless sculptures to be realized in everyscale, material, and price range imaginable for artists ranging from world-renowned to localstudents. Furthermore, Harry has directed projects that have yielded research and/or archivaldata for Museums including the Museum of Modern Art NY, National Gallery of Art, TheBaltimore Museum of Art, the Smithsonian Institution, and many others.Glenn Woodburn - Technical Project ManagerGlenn graduated from Towson University with a Bachelor of Science degree in Industrial Designin 2004. Glenn started working with Direct Dimensions as an intern while at Towson, and washired full-time upon graduation. With 8 years experience, Glenn serves as a technical projectmanager specialized in on-site high-resolution laser scanning projects spanning the art,architecture, historic preservation, film, medical, aerospace, military, and product design worlds.Glenn has extensive knowledge in all current and emerging 3D measurement and digitalmodeling technologies. 3
  • 6. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012Jon Lash - President of Digital AtelierJon Lash is the President of Digital Atelier. He studied at California College of the Arts. Jonworked in Construction Management and Farming before attending Johnson Atelier TechnicalInstitute of Sculpture in Princeton New Jersey. Jon is trained as a sculptor. He was employed atJohnson Atelier as Director of Special Projects for 15 years before starting the Digital Atelier in1998. The Digital Atelier has collaborated with many artists, architects, museums, movieproduction, and design firms over the past 12 years. They are known throughout the industry fortheir technical capabilities and problem solving. 4
  • 7. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012KEY ISSUES, TOPICS, & CONCEPTSData Acquisition: 3-D laser scanning; Data Management: Storage; Data Applications: modeling,reconstruction.INTRODUCTIONIn January 2011, Kreilick Conservation, LLC ofOreland, PA was engaged by Beaver Electric Co. Inc.to conserve the Branch Brook Park Prudential Lions.The Prudential Lions were sculpted by Karl Bitter(1867-1915). Karl Bitter (see Figure 1) was born inVienna, Austria and immigrated to New York City in1889. Bitter worked on a number of notable publicsculpture projects for major architects, includingRichard Morris Hunt and George B. Post. His privatecommissions went to a number of large residences,including the Vanderbilts, Astors, and Rockefellers.Some of his most famous pieces are the bronze gates ofTrinity Church in Manhattan, ornament for Hunt’sAdministration Building at the 1893 World’sColumbian Exposition in Chicago, the decoration forPost’s Wisconsin State Capitol, the Pomona fountainin front of New York’s Plaza Hotel.1 He was Director Figure 1: Karl Bitter (Karl Theodore Francisof Sculpture at the Buffalo Pan-American exposition, Bitter papers, Archives of American Art,the St. Louis World’s Fair, the Panama-Pacific Smithsonian Institution).Exposition, and President of the National Sculpture Society.2The Prudential Lions were installed over the doorway of the Prudential Insurance Company, inNewark, New Jersey, in 1901 (see Figure 2). They were inspired by the lion on the company’s20-year locket, meant to signify both strength and being on guard. After the building wasdemolished, the Lions were installed in Branch Brook Park, Newark, New Jersey in 1959. Theplaques presented upon their installation note that for “more than half a century, this lion, with itstwin companion... stood guard over the doorway of the First Prudential Building... They havewitnessed the growth of Newark from a town to a metropolis.” They spent another half centuryin Branch Brook Park, where they became mascots for the park and the Park Alliance. Childrenplayed on them, vandals painted them. In 2011, the Park Alliance began a facelift of the MusicCourt where the Lions sit.In August 2011, after conservation work had begun on the sculptures, Kreilick Conservation wasengaged by the Branch Brook Park Alliance to create full-scale replicas of the Lions. To1 Barbara J. Mitnick, “Bitter, Karl Theodore Francis,” in Encyclopedia of New Jersey, ed. Maxine N. Lurie and Marc Mappen(Piscataway, NJ: Rutgers University Press, 2004): 78.2 Ferdinand Schevill, Karl Bitter: A Biography Chicago, Ill.: The University of Chicago Press, 1917): xiii. 5
  • 8. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012complete the work, Kreilick Conservation put together a team of 3D documentationprofessionals, including Direct Dimensions, Inc., who undertook laser scanning and 3Dcomputer modeling, and the Digital Atelier, LLC, who used the models for CNC machiningfoam. Figure 2: Entrance to the First Prudential Building in Newark, New Jersey (Prudential). 6
  • 9. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012THE LIONSThe Prudential Lions are carved limestone companion sculptures depicting seated male lions,each with a front paw resting on a sphere (see Figure 3). Each lion sat atop a concrete base. Thebases originally had inscribed plaques which read, “Presented to the citizens of Essex County/bythe Prudential Insurance Company of America/from 1892 to 1958, more than half a century, thislion, with/its twin companion, sculpted by Karl Bitter, stood guard/over the doorway of the FirstPrudential Building in Newark/at 763 Broad Street, corner of Bank Street. They havewitnessed/the growth of Newark from a town to a metropolis.” 3 The Lions are approximatelyseven feet tall and weigh 2,900 pounds each.Before treatment, the limestone sculptures exhibited staining, biological growth, gypsum crusts,graffiti, mechanical damage, spalling, and erosion of details. In the last several years, a series ofpainting campaigns were undertaken to cover these conditions. The Lions were also missingportions of their tails, teeth, claws, and snouts. See Figures 4 – 6 for examples of theseconditions. Figure 3: Prudential Lions in Branch Brook Park before treatment in Newark, New Jersey.3 Smithsonian American Art Museum, “Prudential Lions, (sculpture),” Art Inventories Catalog, http://siris-artinventories.si.edu/ipac20/ipac.jsp?&profile=all&source=~!siartinventories&uri=full=3100001~!326668~!0#focus(accessed January 12, 2011). 7
  • 10. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 Figure 4: Prudential Lion exhibiting staining, biological growth, gypsum crusts, graffiti, mechanical damage, spalling, and erosion of details. 8
  • 11. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 Figure 5: Graffiti paint revealed after paint removal. Figure 6: Graffiti and missing tail. 9
  • 12. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012RESTORATION, DATA COLLECTION, AND REPLICATIONThis project began as a restoration/conservation effort. Treatments such as water-misting, paintremoval, soluble-salt reduction through poulticing, laser cleaning, and Dutchmen repairs wereundertaken (see Figure 7). Then in August 2011, after conservation work had begun, the projectwas expanded to include the creation of full-scale Lion replicas. The shift came from a desire topreserve the original statues for the future. The client wanted to take advantage of their highvisibility for promotional purposes, keep them accessible to the public, while also keeping anaccurate representation of their forms for the future. With these considerations in mind, KreilickConservation presented the client with several options. Firstly, to do nothing beyond restoringand maintaining the originals. Secondly, to make molds of the restored sculptures. Thirdly, tolaser-scan the sculptures and create digital models from which replicas and molds could becreated.Figure 7: Treatments (clockwise from top): paint removal, misting, poulticing, laser cleaning, & Dutchman. 10
  • 13. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012Laser scanning and 3D modeling were eventually selected as the best option. In the past, thesesculptures were subject to vandalism, and wear and tear from park visitors. Some sort ofdocumentation was desirable in anticipation of their continued use in a public space. Creatingmolds from the original statues would have had similar results to 3D modeling, however therewere concerns about the storage and shelf life of large rubber molds, and the effect the mold-making process would have on the porous limestone and new repairs. In contrast, laser scanningcould be done in a single day, in place, and without touching the stone surfaces. 3D modelingfrom the scans could provide a digital record accurate enough to negate the need for molds,while also giving the clients the opportunity to easily create replicas from various materials, atvarious sizes, for preservation and/or promotional purposes. In fact, this capability allowed theBranch Brook Park Alliance to go one step further, to relocate the original sculptures to a saferlocation, and to place replicas back in the park. To complete this work, Kreilick Conservationput together a team of 3D documentation professionals, including Direct Dimensions, Inc., whoundertook the laser scanning and 3D computer modeling, and the Digital Atelier, LLC, who usedthe models for CNC machining foam. These foam forms were ultimately used to create moldsfor the precast concrete replicas.LASER SCANNINGInitially, the client was offered four options for the timing of the laser scanning: 1. The first option would be to scan the lions before they were moved in the event of a catastrophic failure during the de-installation. 2. The second time would be that point at which cleaning and paint stripping was completed, and before physical alteration had begun. In this way, replacement elements (i.e. tails, ears, teeth, etc.) could be modeled digitally before they were sculpted in new limestone or shaped with Jahn Restoration Mortar. In these scans, the sculptures would appear in their aged/weathered condition, providing a record of intact historic fabric. 3. The third time would have been after the lions had been conserved and reconstructed elements had been installed, and deteriorated features and details had been modeled in clay. This scanning would be an alternative to making rubber molds for future replication of the lions. In these scans, the sculptures would be restored recreations of the Lions in 1901, interpretations made by the sculptor from historic images, and client input. This would have to occur at the end of the restoration process. 4. The option that was ultimately chosen: scanning of the lions after cleaning and reconstruction of lost elements in clay, but before permanent repairs were made. For our client, this had two benefits. 1) This allowed for scanning to occur sooner. This meant that work on the STL files, machining of the foam, and creation of precast concrete replicas could occur at the same time Jahn repairs and stone Dutchmen were being installed on the original sculptures. 2) The client wanted to enlist the skills of a sculptor, and to be able to physically view/experience the repairs, to have editorial control over their appearance, before scanning and permanent repairs occurred. 11
  • 14. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012Before scanning, conservators worked with sculptor Pavel Efremoff to restore lost details on thePrudential Lions in clay (see Figure 8). Portions of the manes, ears, eyebrows, snouts, teeth,chin, and claws were recreated (see Figure 9). The work was based on photographicdocumentation from the New Jersey Historical Society, the Newark Public Library, andPrudential Insurance Co. The recreated elements were made available to the owner’srepresentatives for inspection and approval. Adjustments were made based on their commentary. Figure 8: Sculptor making clay repairs. Figure 9: Clay repairs of lost details. 12
  • 15. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012After restoring lost details on the Prudential Lions in clay, Direct Dimensions, Inc. came to theconservation studio to laser scan the statues. A Surphaser® 25HSX, a phase shift, hemispherical3D scanner, was utilized (see Figure 10). This scanner has a 360° x 270° field-of-view and scanrate of up to 800,000 points per second. The scanner creates 3-dimensional electronic imagesthat are accurate up to 1mm or better. This scanner collects point data to create polygonalcomputer models (STL files, see Figure 11). These files were edited by the Direct Dimensionstechnician to ensure accuracy and to fix any gaps in the data (see Figure 12). Scanning thestatues after clay repairs allowed work on the 3D and foam models to continue simultaneouslywith conservation work on the original statues, including Jahn mortar repairs, stone Dutchmen,and consolidation. In contrast, mold-making would have had to have occurred either on the un-restored stone surfaces, meaning any replicas would not reflect the statues’ restored appearances,or on newly patched and repaired stone surfaces, which would be vulnerable to damage duringthe mold-making process. Figure 10: Direct Dimensions laser scanning lion statue. 13
  • 16. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 Figure 11: Direct Dimensions laser scanning lion statue. Figure 12: Polygonal computer model created from laser scanning. 14
  • 17. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012CNC MACHININGAfter laser scanning, the finished STL files were given to the Digital Atelier in Mercerville, NJ.There a five-axis CNC (digitally automated via computer numerical control) machine was usedto mill full-scale foam replicas in 6 lb. urethane foam (see Figure 13).Kreilick Conservation worked with the Digital Atelier on the construction of the foam forms andthe finishing of their surfaces. Each of the Lions were created in eleven separate pieces of foam(see Figure 14). After the pieces were glued together, the surfaces required reworking. Asexcellent as the technology is, there is still a need for artistic involvement. The bits used to cutthe hard foam are not able to cut any deeper than they are wide, so recesses and overhangs werenot as deep as in the original sculptures. In addition, even the smallest bits used by themechanical cutting machine leave a regular groove pattern across the surface that needed to becarved back and minimized. As such, conservators and a sculptor worked with the DigitalAtelier staff to rework the entire surface of each lion and to redefine the recesses, whilereferencing historic photos and restoration photos.The finished foam figures were used by Metropole, Inc. to create molds for casting replicas (seeFigure 15). In this way, new precast concrete statues were created without endangering theoriginal limestone figures at any point in the process. The results of this process were two pre-cast concrete replicas that could be placed in Branch Brook Park, while the restored originalswere relocated to the Newark Hall of Records. Figure 13: CNC machine at the Digital Atelier milling foam lions. 15
  • 18. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 Figure 14: Foam model, after compiling pieces and before painting. Figure 15: Metropoles mold making process. 16
  • 19. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012CONCLUSIONSThis project demonstrates a case in which 3D digital documentation provides the best and mostappropriate option for a conservation project. The advantages proved greater than those for moretraditional methods of documentation, including 2-dimensional drawings, photographicdocumentation, and mold-making. Nonetheless, there were disadvantages, largely to do withcosts, technological abilities of the client, and loss of detail in replicas, that had to be considered.Benefits: 1. Physical storage - this eliminates the need to store large rubber molds in a controlled environment. 2. Long-term storage - the files are stored digitally. 3. Relative ease of manipulation - in future, the files can be manipulated to make changes to the models, to make enlargements or miniatures, and to make castings in a variety of materials (i.e. bronze, aluminum, cast stone, glass fiber-reinforced concrete (GFRC), fiberglass resin, etc.). 4. Accuracy 5. Protection of original fabric - the porous, weathered limestone. 6. Protection of new repairs - Jahn repairs and limestone Dutchmen.Disadvantages: 1. Costs of technology - may be comparable between mold storage and digital file/foam creation. 2. Costs of accuracy - choice of accuracy determined the degree of artistic finishing, but increased accuracy requires increased expenses, so there is a trade-off in paying for accuracy and paying for the involvement of an artist. 3. Changes in technology - must keep files up to date with the technology to read them, and/or have access to the necessary technology. 4. File size and storage - large files for client to store. 5. Loss of detail in replicas - one drawback to the scanning, machining, and reworking process was that the surface texture and eroded beddings planes of the limestone originals were minimized in the final products. In each stage, some degree of surface detail was lost, giving the foam figures and precast concrete replicas a smoother appearance. In this case, however, the client was willing to accept some degree of difference, since the replicas are recreations of the original forms, rather than exact replicas of the statues in their current state. 6. Not exact replicas - scanning was done on the clay repairs, which included more detail than the permanent Jahn repairs. Jahn repairs require the loss of original material to create appropriate surfaces for patching, so fewer Jahn repairs were made than clay repairs. See Figures 21 & 22 for a side-by-side comparison of the original lions with Jahn repairs, and the pre-cast concrete replicas made from the clay repairs, laser scanning, foam models, and molds. 17
  • 20. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 Figure 16: South lion, Pat, before treatment. Figure 17: South lion, Pat, precast concrete replica. 18
  • 21. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012 Figure 20: Replicas in place in Branch Brook Park. Figure 18: South lion, Pat, before treatment. Figure 19: South lion, Pat, precast concrete replica. 19
  • 22. Restoring the Lions’ Roar Kreilick Conservation, LLC3D Digital Documentation Summit 11 July 2012Figure 21: Original limestone lion after treatment. Figure 22: South lion, Pat, precast concrete replica. 20