Another method of removing glass panels that has proven to be effective if the solvent-and-wire method cannor be used involves directing steam at the face of the panel in order to soften the mastic.

Although this method can be time-consuming, averaging up to 10 minutes per panel, the glass can be successfully removed. Remaing mastic may then be removed by directing additional steam on the panel, soaking the panels in hot water to further soften the mastic--or applying appropriate chemical sovents--and scraping off the softened mastic.

Reinstallation of Glass Panels

  Due to an accumulation of soot behind the glass, the surface of the masonry substrate usually needs to be cleaned before panels or a wall of pigmented structural glass are reinstalled.

After removal of the glass panels has been completed, the substrate should be cleaned using a mild derergent and water, then allowed sufficient time to dry. The old glass must also be thoroughly cleaned of soot, grease, or old mastic that would impair bonding of the new adhesive. A mild solution of water and household ammonia will generally clean the surface adequately. The glass may then be reinstalled following a system established during removal.

 In reinstalling the glass panels (or new panels to replace any historic glass that has been broken), it is recommended that the mastic adhesive used throughout the 1930s and 1940s be used, because it is still the best bonding material. Although modern silicone compounds offer workability, adhesion, and flexibility, they tend to be expensive when used in the necessary quantity. On the other hand, butyl adhesives do not provide sufficient adhesion on nonporous materials such as pigmented structural glass. Polysulfide-based, synthetic rubber sealants do not have the short set-up time of the traditional hot-melt asphalt mastic and thus present installation difficulties. Finally, epoxies do not appear to have the plasticity essential for longevity of a glass veneer.