Stained glass

Lorraine Schnabel <rainyroon [at] verizon__net> writes

>Lisa Fox <lisa.fox [at] sos__mo__gov> writes
>
>>>...  My parish has allocated money for a significant project
>>>to restore our stained-glass windows.  We have discovered that some
>>>of the lead is deteriorating, and the wood around some of the
>>>windows is rotting. We also plan to replace the deteriorating,
>>>yellowed Lexan (?) with a newer protective covering.
>
>I would also urge you to avoid epoxy repairs to the wood wherever
>possible. If skilled carpenters are available, wood dutchman repairs
>using similar species will perform much better over the long-term.
>Of course, complicated traceries and predominantly old-growth wood
>make the concept of epoxy repairs more tolerable for vertical
>surfaces. Regardless, my personal opinion is that wood window sills
>should never be repaired with epoxy.

I can understand this statement from the point of view of the
history of some epoxy repairs. However, I view most of these problem
epoxy repairs as cases where the repair process did not understand
and take into account the original cause of the problem, as well as
the on-going existing conditions/environment. Too many times the
repair, whether it is with traditional materials and techniques or
some modern substitute, is made without considering the cause of the
problem. A deteriorated area of wood window sill is repaired without
maintaining the joint between window jamb and sill so that sooner or
later water gets in and starts the deterioration process all over
again. Or the wood is repaired and the conditions that caused
condensation on the interior side of the protective glazing is not
corrected and the moisture/deterioration cycle starts all over
again. If there is deterioration, I recommend that the assumption
should be that it *will* reoccur. This means that introducing a
maintenance element to the on-going process is extremely important.

I have used epoxy for the repair of wood since 1975. Its use or
non-use is more a process of what is the philosophy of the site in
relation to preserving historic materials and or preserving
traditional methods and techniques. As with any repair, it might be
advisable to pre-treat replacement wood with borate based wood
preservatives to help overcome some of the deferred maintenance that
will occur. One of the real problems with the use of epoxy is that
many times it will be spread on the surface of the wood thinking
that will magically protect it. If moisture or wood boring insects
are able to get behind the epoxy then quite a bit of deterioration
can occur prior to being visible on the surface due to the epoxy
reinforcement of the wood surface.  This means when the
deterioration is finally noticed it can be a surprise to see how
extensive it has become.

Too many times the maintenance and repair of historic or important
sites is viewed as a remodeling project and not as a
preservation/conservation project. The buildings are not given the
same level of respect that the individual items on display within
the structure are given. If the historic material is important
because it shows the tool marks or past hardware locations,
replacing with a wood patch will eliminate that information. It
could be viewed in the same light as tearing out a page from a book.
If the building is a good example of historic materials and
techniques, it may be appropriate to replace deteriorated elements
with similar material and techniques in order to preserve the
physical craft. If neither is important then additional repair
options may be available. Whatever the repair is, if the cause of
the problem is not dealt with, deterioration will reoccur.  And if
maintenance is not part of the process, deterioration will occur.

I would hope that we view materials and techniques as appropriate or
not appropriate in relation to a specific application and not
wholesale statements based on poor understanding, bad specs and/or
less than knowledgeable workmanship. This mean the people making the
choices need to deal with the whole picture and not just
generalizations.

Bryan Blundell
Dell Corporation
PO Box 1462
Rockville, MD 20849
301-279-2612


                                  ***
                  Conservation DistList Instance 21:15
                   Distributed: Sunday, July 8, 2007
                       Message Id: cdl-21-15-004
                                  ***