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

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

Restoring the Lions’ Roar Kreilick Conservation, LLC
3D 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,

T. SCOTT KREILICK, PRESIDENT/CEO/PRINCIPAL CONSERVATOR,

HARRY ABRAMSON, PROJECT MANAGER,
DIRECT DIMENSIONS, INC.

GLENN WOODBURN, TECHNICAL PROJECT MANAGER,
DIRECT DIMENSIONS, INC.

JON LASH, PRESIDENT/CEO,
DIGITAL ATELIER, LLC

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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

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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) ............................................................................................................. 5
Figure 2: Entrance to the First Prudential Building in Newark, New Jersey (Prudential).............. 6
Figure 3: Prudential Lions in Branch Brook Park before treatment in Newark, New Jersey. ........ 7
Figure 4: Prudential Lion exhibiting staining, biological growth, gypsum crusts, graffiti,
mechanical damage, spalling, and erosion of details. ............................................................. 8
Figure 5: Graffiti paint revealed after paint removal. ..................................................................... 9
Figure 6: Graffiti and missing tail................................................................................................... 9
Figure 7: Treatments (clockwise from top): paint removal, misting, poulticing, laser cleaning, &
Dutchman. ............................................................................................................................. 10
Figure 8: Sculptor making clay repairs. ........................................................................................ 12
Figure 9: Clay repairs of lost details. ............................................................................................ 12
Figure 10: Direct Dimensions laser scanning lion statue.............................................................. 13
Figure 11: Direct Dimensions laser scanning lion statue.............................................................. 14
Figure 12: Polygonal computer model created from laser scanning............................................. 14
Figure 13: CNC machine at the Digital Atelier milling foam lions. ............................................. 15
Figure 14: Foam model, after compiling pieces and before painting. .......................................... 16
Figure 15: Metropole's mold making process. .............................................................................. 16
Figure 16: South lion, Pat, before treatment. ................................................................................ 18
Figure 17: South lion, Pat, precast concrete replica...................................................................... 18
Figure 18: South lion, Pat, before treatment. ................................................................................ 19
Figure 20: Replicas in place in Branch Brook Park. ..................................................................... 19
Figure 21: Original limestone lion after treatment. ...................................................................... 20

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BIOGRAPHIES

Caitlin Smith - Project Conservator
Caitlin Smith is an architectural and sculptural conservator for Kreilick Conservation, LLC. She
received a Master of Science in Historic Preservation from the University of Pennsylvania, and
undergraduate degrees in Historic Preservation and Political Science from the University of
Mary Washington. Her graduate thesis, Cleaning Methods for the Removal of Limewash from
Painted Plaster Surfaces: Utilizing Ion Exchange Resins on the Interior Architectural Finishes of
the Capilla de Nuestra Señora del Rosario in Iglesia San José in San Juan, Puerto Rico, was
presented at the IIC 2010 Congress and the APT 2009 Conference. She has worked with the
Architectural Conservation Laboratory at the University of Pennsylvania, the Fairmount Park
Historic Preservation Trust, the Jekyll Island Historic Preservation Internship Program, Kenmore
Mansion, and the US/ICOMOS International Exchange Program.

T. Scott Kreilick - Principal Conservator & Project Manager
T. Scott Kreilick is President, CEO, and Principal Conservator of Kreilick Conservation, LLC
located in Oreland, PA. Scott is a Professional Associate of the American Institute for
Conservation of Historic and Artistic Works (AIC). Scott earned his MS in Historic Preservation
with a Specialization in Architectural Conservation from the University of Pennsylvania; and his
BA in the History and Sociology of Science, also from the University of Pennsylvania.
Established in 1996, Kreilick Conservation, LLC provides condition assessments, laboratory and
field analysis of materials, emergency response and stabilization, treatment, documentation, and
maintenance of architecture, monuments, sculpture, and objects, with a specialization in metals
and stone.

Harry Abramson - Project Manager
Harry graduated from James Madison University in 1989 with a Bachelor of Science Degree in
Economics. With a career in technical sales and project management along with a love and
respect for the arts, Harry joined Direct Dimensions in 2004 to develop technical solutions
serving the art industry. Harry’s work has helped countless sculptures to be realized in every
scale, material, and price range imaginable for artists ranging from world-renowned to local
students. Furthermore, Harry has directed projects that have yielded research and/or archival
data for Museums including the Museum of Modern Art NY, National Gallery of Art, The
Baltimore Museum of Art, the Smithsonian Institution, and many others.

Glenn Woodburn - Technical Project Manager
Glenn graduated from Towson University with a Bachelor of Science degree in Industrial Design
in 2004. Glenn started working with Direct Dimensions as an intern while at Towson, and was
hired full-time upon graduation. With 8 years experience, Glenn serves as a technical project
manager 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 digital
modeling technologies.

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Jon Lash - President of Digital Atelier
Jon Lash is the President of Digital Atelier. He studied at California College of the Arts. Jon
worked in Construction Management and Farming before attending Johnson Atelier Technical
Institute of Sculpture in Princeton New Jersey. Jon is trained as a sculptor. He was employed at
Johnson Atelier as Director of Special Projects for 15 years before starting the Digital Atelier in
1998. The Digital Atelier has collaborated with many artists, architects, museums, movie
production, and design firms over the past 12 years. They are known throughout the industry for
their technical capabilities and problem solving.

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KEY ISSUES, TOPICS, & CONCEPTS

Data Acquisition: 3-D laser scanning; Data Management: Storage; Data Applications: modeling,
reconstruction.

INTRODUCTION

In January 2011, Kreilick Conservation, LLC of
Oreland, 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 in
Vienna, Austria and immigrated to New York City in
1889. Bitter worked on a number of notable public
sculpture projects for major architects, including
Richard Morris Hunt and George B. Post. His private
commissions went to a number of large residences,
including the Vanderbilts, Astors, and Rockefellers.
Some of his most famous pieces are the bronze gates of
Trinity Church in Manhattan, ornament for Hunt’s
Administration Building at the 1893 World’s
Columbian Exposition in Chicago, the decoration for
Post’s Wisconsin State Capitol, the Pomona fountain
in front of New York’s Plaza Hotel.1 He was Director Figure 1: Karl Bitter (Karl Theodore Francis
of 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.2

The Prudential Lions were installed over the doorway of the Prudential Insurance Company, in
Newark, New Jersey, in 1901 (see Figure 2). They were inspired by the lion on the company’s
20-year locket, meant to signify both strength and being on guard. After the building was
demolished, the Lions were installed in Branch Brook Park, Newark, New Jersey in 1959. The
plaques presented upon their installation note that for “more than half a century, this lion, with its
twin companion... stood guard over the doorway of the First Prudential Building... They have
witnessed the growth of Newark from a town to a metropolis.” They spent another half century
in Branch Brook Park, where they became mascots for the park and the Park Alliance. Children
played on them, vandals painted them. In 2011, the Park Alliance began a facelift of the Music
Court where the Lions sit.

In August 2011, after conservation work had begun on the sculptures, Kreilick Conservation was
engaged by the Branch Brook Park Alliance to create full-scale replicas of the Lions. To

1 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.

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complete the work, Kreilick Conservation put together a team of 3D documentation
professionals, including Direct Dimensions, Inc., who undertook laser scanning and 3D
computer modeling, and the Digital Atelier, LLC, who used the models for CNC machining
foam.

Figure 2: Entrance to the First Prudential Building in Newark, New Jersey (Prudential).

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THE LIONS

The 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. The
bases originally had inscribed plaques which read, “Presented to the citizens of Essex County/by
the Prudential Insurance Company of America/from 1892 to 1958, more than half a century, this
lion, with/its twin companion, sculpted by Karl Bitter, stood guard/over the doorway of the First
Prudential Building in Newark/at 763 Broad Street, corner of Bank Street. They have
witnessed/the growth of Newark from a town to a metropolis.” 3 The Lions are approximately
seven 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 of
painting campaigns were undertaken to cover these conditions. The Lions were also missing
portions of their tails, teeth, claws, and snouts. See Figures 4 – 6 for examples of these
conditions.

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).

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Figure 4: Prudential Lion exhibiting staining, biological growth, gypsum crusts, graffiti,
mechanical damage, spalling, and erosion of details.

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Figure 5: Graffiti paint revealed after paint removal.

Figure 6: Graffiti and missing tail.

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RESTORATION, DATA COLLECTION, AND REPLICATION

This project began as a restoration/conservation effort. Treatments such as water-misting, paint
removal, soluble-salt reduction through poulticing, laser cleaning, and Dutchmen repairs were
undertaken (see Figure 7). Then in August 2011, after conservation work had begun, the project
was expanded to include the creation of full-scale Lion replicas. The shift came from a desire to
preserve the original statues for the future. The client wanted to take advantage of their high
visibility for promotional purposes, keep them accessible to the public, while also keeping an
accurate representation of their forms for the future. With these considerations in mind, Kreilick
Conservation presented the client with several options. Firstly, to do nothing beyond restoring
and maintaining the originals. Secondly, to make molds of the restored sculptures. Thirdly, to
laser-scan the sculptures and create digital models from which replicas and molds could be
created.

Figure 7: Treatments (clockwise from top): paint removal, misting, poulticing, laser cleaning, & Dutchman.

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Laser scanning and 3D modeling were eventually selected as the best option. In the past, these
sculptures were subject to vandalism, and wear and tear from park visitors. Some sort of
documentation was desirable in anticipation of their continued use in a public space. Creating
molds from the original statues would have had similar results to 3D modeling, however there
were 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 scanning
could be done in a single day, in place, and without touching the stone surfaces. 3D modeling
from 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, at
various sizes, for preservation and/or promotional purposes. In fact, this capability allowed the
Branch Brook Park Alliance to go one step further, to relocate the original sculptures to a safer
location, and to place replicas back in the park. To complete this work, Kreilick Conservation
put together a team of 3D documentation professionals, including Direct Dimensions, Inc., who
undertook the laser scanning and 3D computer modeling, and the Digital Atelier, LLC, who used
the models for CNC machining foam. These foam forms were ultimately used to create molds
for the precast concrete replicas.

LASER SCANNING

Initially, 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.

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Before scanning, conservators worked with sculptor Pavel Efremoff to restore lost details on the
Prudential 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 photographic
documentation from the New Jersey Historical Society, the Newark Public Library, and
Prudential Insurance Co. The recreated elements were made available to the owner’s
representatives for inspection and approval. Adjustments were made based on their commentary.

Figure 8: Sculptor making clay repairs. Figure 9: Clay repairs of lost details.

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After restoring lost details on the Prudential Lions in clay, Direct Dimensions, Inc. came to the
conservation studio to laser scan the statues. A Surphaser® 25HSX, a phase shift, hemispherical
3D scanner, was utilized (see Figure 10). This scanner has a 360° x 270° field-of-view and scan
rate of up to 800,000 points per second. The scanner creates 3-dimensional electronic images
that are accurate up to 1mm or better. This scanner collects point data to create polygonal
computer models (STL files, see Figure 11). These files were edited by the Direct Dimensions
technician to ensure accuracy and to fix any gaps in the data (see Figure 12). Scanning the
statues after clay repairs allowed work on the 3D and foam models to continue simultaneously
with 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 during
the mold-making process.

Figure 10: Direct Dimensions laser scanning lion statue.

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Figure 11: Direct Dimensions laser scanning lion statue.

Figure 12: Polygonal computer model created from laser scanning.

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CNC MACHINING

After 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 used
to 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 and
the 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. As
excellent as the technology is, there is still a need for artistic involvement. The bits used to cut
the hard foam are not able to cut any deeper than they are wide, so recesses and overhangs were
not as deep as in the original sculptures. In addition, even the smallest bits used by the
mechanical cutting machine leave a regular groove pattern across the surface that needed to be
carved back and minimized. As such, conservators and a sculptor worked with the Digital
Atelier staff to rework the entire surface of each lion and to redefine the recesses, while
referencing historic photos and restoration photos.

The finished foam figures were used by Metropole, Inc. to create molds for casting replicas (see
Figure 15). In this way, new precast concrete statues were created without endangering the
original 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 originals
were relocated to the Newark Hall of Records.

Figure 13: CNC machine at the Digital Atelier milling foam lions.

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Figure 14: Foam model, after compiling pieces and before painting.

Figure 15: Metropole's mold making process.

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CONCLUSIONS

This project demonstrates a case in which 3D digital documentation provides the best and most
appropriate option for a conservation project. The advantages proved greater than those for more
traditional methods of documentation, including 2-dimensional drawings, photographic
documentation, and mold-making. Nonetheless, there were disadvantages, largely to do with
costs, 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.

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Figure 16: South lion, Pat, before treatment. Figure 17: South lion, Pat, precast concrete replica.

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Figure 20: Replicas in place in Branch Brook Park.

Figure 18: South lion, Pat, before treatment. Figure 19: South lion, Pat, precast concrete replica.

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Figure 21: Original limestone lion after treatment. Figure 22: South lion, Pat, precast concrete replica.

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