U.S. General Services Administration
Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
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We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
REFERENCE:
New York Landmarks Conservancy. “Restoring Scaliola to Glory”, Common Bond, Vol.18, No.1 and 2, Fall-Winter 2003.
PART 1–GENERAL
1.01 SUMMARY
A. This procedure includes guidance on consolidating
delaminated scagliola. Delamination may be caused by a
flaw in the original manufacture of the material. This
could include the use of glue water in the manufacture,
the use of different types or gauges of plaster for the
color coat and backing, the improper placement of the
burlap, extreme temperature changes, or the presence of
excessive amounts of moisture.
NOTE: THIS PROCEDURE SHOULD ONLY BE PERFORMED BY AN
EXPERIENCED CONSERVATOR.
B. For general information on scagliola, including its
characteristics, uses and problems, see 09200-05-S.
C. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Submittals
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).
PART 2–PRODUCTS
2.01 MANUFACTURERS
A. StanChem www.stanchem.com
B. Museum Services Corporation www.museumservicescorporation.com
C. Sika Corporation usa.sika.com
2.02 MATERIALS
A. Acrylic lacquer such as “Acryloid B-72” (10% solution) or
“Incralac” (StanChem), (Museum Services Corp.),
or approved equals.
-or-
B. Low-modulus epoxy resin such as “Sikadur Lo Mod” (Sika),
or approved equal.
C. Clean, potable water
D. Clean, cotton cloths
2.03 EQUIPMENT
A. Spray gun, Binks or DeVilbiss with accessories; for
example, DeVilbiss bleeder, external mix gun with cup, or
approved equal.
B. Air compressor, small, portable, either gas (for exterior
use) or electric (if electricity is accessible), or
electric compressor powered by a portable generator.
C. Accessories: air hoses adequate for reaching all parts
of surface, couplers, repair kit for spray gun, small
moisture traps.
D. Organic vapor masks, basic safety equipment to protect
operator from breathing vapors or organic solvents during
spray application.
E. Goggles, to protect operator’s eyes from lacquer.
F. Gloves, neoprene rubber or polyethylene disposable
gloves. Skin contact with lacquer should be avoided.
PART 3–EXECUTION
3.01 EXAMINATION
A. Verification of Conditions:
1. Determine the cause of delamination. Is there
evidence of extreme temperature changes or
excessive moisture? Is the cause of delamination
due to an inherent flaw in the original
manufacture?
2. Determine which type of scagliola it is - true scagliola
or marezzo. THIS WILL REQUIRE A CONSERVATOR’S
EXPERTISE. The biggest difference lies in how each
is manufactured, applied and finished. Marezzo is
made in reverse order from the way true scagliola is
produced and is generally a less labor-intensive
process. Recognizing the difference between the
two can aid in better understanding the problem or
failure. The typical polish used for each type is
also significant, as some polishes have proven to
be detrimental to the material.
3.02 PREPARATION
A. Surface Preparation:
1. ALWAYS test repair methods in an inconspicuous area
to determine the effects of the method on the
material and whether this procedure is suitable for
use in this situation.
2. Wash area to be consolidated to remove all surface
dirt, grease and foreign matter.
a. Wipe the surface with a clean cloth saturated
in clean, clear water and mild detergent. DO
NOT FLOOD ENTIRE SURFACE, SIMPLY WIPE AFFECTED
AREA.
b. Thoroughly rinse the surface with clean, clear
water and allow to dry.
3.03 ERECTION, INSTALLATION, APPLICATION
A. Apply multiple thin layers of acrylic lacquer to the
delaminated surface using a spray gun. IMPORTANT: AIR
PRESSURE OF GUN MUST BE ADJUSTED TO THE VISCOSITY OF THE
MATERIAL AND TYPE OF GUN USED.
NOTE: BRUSH-APPLIED COATINGS ARE NOT ACCEPTABLE. THEY
DO NOT PROVIDE UNIFORM COVERAGE.
1. Apply first coat in a thin mist. Solution should
be naturally drawn into the scagliola by capillary
action.
2. Hand-rub surface with wet or dry sandpaper using
water as a lubricant.
3. Continue to apply thin wet coats to the surface,
hand-rubbing between coats as above.
-OR-
B. Inject a low-modulus epoxy resin into the scagliola.