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.

One should think very seriously before introducing an adhesive into
a "blind" crack in glass.  This intervention should be considered
irreversible, as the removal of the adhesive will certainly endanger
the glass and may cause additional expansion of the crack from
swelling of the adhesive.  I do not recommend the epoxies for this
reason (and what was already mentioned, the yellowing problem).  I
am also not an advocate of UV-setting adhesives, as I believe their
stability to be limited.  If I saw the need to stabilize a crack of
this nature, I would inject a solution of Acryloid B-72, in either
acetone:ethanol (80:20), or in toluene (one of my only uses for this
noxious solvent).  The concentration would depend on the width of
the crack and ambient application conditions.  I would accept the
very slight visual incongruity resulting from the differing
refractive index and eventual air bubbles (from solvent
evaporation).

                                  ***
                  Conservation DistList Instance 12:14
                   Distributed: Friday, July 31, 1998
                       Message Id: cdl-12-14-002
                                  ***