Effect of low temperature on paintings

I work in a private conservation studio; for the last months we have
been using a system to eliminate any kind of biological attack to
organic materials. We put the infected material in a hermetic
chamber. It slowly lowers temperature down to -23 deg. C, then holds
it for 12 hours and starts raising till it reaches the same
temperature out and then we open the chamber. Humidity is also
controlled.

The problem we have is that we are not sure of the safety of this
system on polychromatic wood or canvas with or without preparation.
We have tried this with old wooden gilded frames and nothing *seems*
to happen.  Maybe cold would affect priming, or paint, maybe it
would crack--we do not know what may happen in a medium/long term
after this treatment. It would help us very much if anyone could
give us some advise about this.

Belin Lahoz
Paintings restorer (Tratteggio SL)
Spain



                                  ***
                  Conservation DistList Instance 14:48
                 Distributed: Thursday, March 22, 2001
                       Message Id: cdl-14-48-014
                                  ***