Repairing Hairline Cracks In Pigmented Structural Glass Panels

CSI Division
Division 8 - Openings
Section
Glass
Last Modified

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.

Part 1–General

1.01 Summary

  1. This procedure includes guidance on patching minor cracks (smaller than 1/16” wide) in pigmented structural glass panels.
  2. See also 08810-01-S, 08810-02-R and 08810-03-R for additional guidance on the preservation of pigmented structural glass.
  3. 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

  1. 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.
  2. 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

  1. 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

  1. Regulatory requirements: Comply with municipal and federal regulations governing all work included in this procedure.

Part 2–Products

2.01 Materials

  1. Water: Potable, non-staining and free of oils, acids, alkalis and organic matter.
  2. 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.
  3. Cleaning agent for structural glass: Application for removal of soil and grease build-up. Use a mild solution of water mixed with potable ammonia.
  4. 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

  1. 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

  1. 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.
  2. Blend the caulking compound to match the color of the adjacent structural glass by adding pigment.
  3. 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.
  4. 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.
  5. 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.
  6. Rinse off all cleaned structural glass panels with a water solution.
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Last updated: Aug 1, 2025
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