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Historic Preservation - Technical Procedures

Spectitle:

Repairing Hairline Cracks In Pigmented Structural Glass Panels

Procedure code:

0881001R

Source:

National Capitol Region Specifications

Division:

Doors And Windows

Section:

Glass

Last Modified:

02/24/2012

Details:

Repairing Hairline Cracks In Pigmented Structural Glass Panels



REPAIRING HAIRLINE CRACKS IN PIGMENTED STRUCTURAL GLASS PANELS


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on patching minor cracks
         (smaller than 1/16" wide) in pigmented structural glass
         panels.

    B.   See also 08810-01-S, 08810-02-R and 08810-03-R for
         additional guidance on the preservation of pigmented
         structural glass.

    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).

1.02 DEFINITIONS

    A.   Work Description: Prior to commencing the work, the
         Contractor shall submit to the Contracting Officer's
         representative a written description of the entire
         methods and procedures proposed for all the work to be
         carried out to the structural glass.

    B.   Work Description: Prior to commencing the cleaning
         operations, the Contractor shall submit to the
         Contracting Officer's representative a written
         description of the entire methods and procedures proposed
         for cleaning the structural glass including, but not
         limited to, methods of grinding, sanding and polishing,
         drying times and methods, method of sealing and proposed
         protection and handling procedures.

1.03 SYSTEM DESCRIPTION

    A.   Performance Requirements:

         1.   The general objective for structural glass repair
              and replacement is to match the pigment and all
              aspects of the structural glass with the original
              in all respects.

         2.   The general objective of structural glass cleaning
              is to remove dirt, grime and coatings from the
              surface without damaging the underlying material
              and to give all the structural glass a clean
              uniform appearance without blotches.

1.04 QUALITY ASSURANCE

    A.   Regulatory Requirements: Comply with municipal and
         Federal regulations governing all work included in this
         procedure.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Water: Potable, non-staining and free of oils, acids,
         alkalis and organic matter.

    B.   Pigments: Pure mineral earth pigments resistant to
         alkalis and non-fading. Suitable colors are to be
         selected to match existing in all respects, to the
         standard of the approved samples.

    C.   Cleaning Agent for Structural Glass: Application for
         removal of soil and grease build-up. Use a mild solution
         of water mixed with potable ammonia.

    D.   Joint Cement or Caulking Compound: Application for
         filling narrow 1/16" to 1/32" joints between structural
         glass.

         1.   Use a joint compound with an integrated watertight
              surface, capable of being used int he narrow joints
              described above.


PART 3---EXECUTION

3.01 PREPARATION

    A.   Surface Preparation:  Clean the existing substrate
         thoroughly with a light detergent or mild chemical wash
         to remove all built-up soiling. Allow substrate to dry
         out fully prior to installation of structural glass
         panels.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Remove all foreign matter from the void. Remove all
         sealer from the surfaces adjacent to the void with a mild
         solution of water mixed with ammonia. Allow to dry out
         fully prior to adding the epoxy resin.

    B.   Blend the caulking compound to match the color of the
         adjacent structural glass by adding pigment.

    C.   Force the caulking compound into the void, making sure it
         is pressured into the crack as deep as possible. Fill the
         cracks neatly and avoid spreading the caulking compound
         over the adjacent structural glass surfaces, to minimize
         necessary clean up.

    D.   When the material has hardened, remove excess caulking
         compound using the manufacturer's specified solvent. This
         should be applied sparingly to a clean rag and the glass
         wiped clean and dry.

    E.   Thoroughly clean all the structural glass panels with a
         mild solution of water and household ammonia using a
         cotton rag. No abrasive cleaning rags are to be used.

    F.   Rinse off all cleaned structural glass panels with a
         water solution.
   
                         END OF SECTION