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.
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.
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.
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
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.