Adhesive for glass

Robert K. MacDowell <macdowell_r [at] mediasoft__net> writes

>Occasionally we are faced with important items of glassware having
>cracks that do not result in actual breakage of the object. We would
>like a good approach to wicking an adhesive into the cracks and
>having it cure slowly (to allow the wicking process time to
>complete).  I am not enthusiastic about the use of epoxy because of
>the risk of yellowing.

We have been using Hxtal NYL-1 for a few years and are quite happy
with the results. It was developed by Herbert Hillary of Austin
Texas in 1981-1982 and was developed specifically for glass. It has
the same light refractory index as glass and its viscosity is quite
loose allowing the material to wick into a hairline crack. When
prepared properly (no contaminations, in a glass jar with a glass
mixing rod), Hxtal is less likely to yellow than any other epoxy
including Epotek-301 (Journal of Conservation Studies 1986 or 87).
Stephan Koob also suggests that Hxtal can be used with a B-72
barrier coat without increasing yellowing .

Hxtal also sets slowly (at 75 degrees F, it requires about 7 days to
achieve 90% of its ultimate bond strength) allowing one to realign a
joint if need be. It can also accept dyes which was used when the
Portland vase was redone a few years back. Hope this helped,

Craig Deller
The Deller Conservation group, Ltd
Geneva, Illinois  USA

                                  ***
                  Conservation DistList Instance 12:14
                   Distributed: Friday, July 31, 1998
                       Message Id: cdl-12-14-003
                                  ***