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Historic Preservation - Technical Procedures

Spectitle:
Consolidating Delaminated Scagliola

Procedure code:
0920006R

Source:
Interior's Handbook For Historic Buildings - Jeff Greene

Division:
Finishes

Section:
Lath & Plaster

Last Modified:
02/24/2012

Details:
Consolidating Delaminated Scagliola



CONSOLIDATING DELAMINATED SCAGLIOLA


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:

         1.   Safety Precautions

         2.   Historic Structures Precautions

         3.   Submittals

         4.   Quality Assurance

         5.   Delivery, Storage and Handling

         6.   Project/Site Conditions

         7.   Sequencing and Scheduling

         8.   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.   Stanley Chemical Co.
         401 Berlin Street
         East Berlin, CT  06023
         203/828-0571

    B.   Conservation Materials
         P.O. Box 2884
         Sparks, NV  89431
         702/331-0582

    C.   Maas & Waldstein Co.
         Division of Seagroves Coatings Corp.
         P.O. Box 187
         320 Paterson Plank Road
         Carlstadt, NY  07072
         800/426-0496

    D.   Custom Aerosal Packaging
         128 East Water Street
         Piqua, OH  45356
         800/237-6765

    E.   Sika Corporation
         201 Polito Ave.
         Lyndhurst, NJ  07071
         201/933-8800
         Sikadur

2.02 MATERIALS

    A.   Acrylic lacquer such as "Acryloid B-72" (10% solution) or
         "Incralac" (Stanley Chemical Co.), (Conservation
         Materials), (Maas & Waldstein Co.), (Custom Aerosal
         Packaging), or approved equal.  Available in spray cans
         or 5-gallon drums.

         -or-

    B.   Low-modulous epoxy resin such as "Sikadur Lo Mod" (Sika
         Chemical Corporation), 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 scag
              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 scag 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 scag 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-modulous epoxy resin into the scag.

                         END OF SECTION