Furniture damaged by fire

Melissa Carr <hiattcarr [at] earthlink__net> writes

>I am preparing to treat a carved and turned arm chair that was badly
>damaged in a fire.  In addition to the effects of water, heat and
>soot on the finish remnants there is evidence of combustion and
>charring of the wood.  The curators intend to display it "as-is" but
>want to ensure that the surface is reasonably stable and will not
>shed friable material in the future. ...

I have recently completed the treatment of a fire-damaged, Victorian
sewing table where consolidation of localized charring was a main
concern.  A literature search for precedent treatments turned up
relatively little published information on similar treatments with
the exception of Kim Cullen Cobb's informative article on the
subject.  As such, I also considered resins and methodologies that
had been used to consolidate biodeteriorated, and archaeological
wood. Discussions with colleagues also led to an investigation of
several epoxies.

Charred surfaces were present on the lid, apron and base of the
object.  Charring on the base was limited to the finish and was
successfully consolidated with B-72.  The veneer on the front of the
apron was lost entirely but the substrate was only superficially
scorched and was consolidated with hide glue sizing.  The most
problematic aspect of the treatment was the need to consolidate
varying layers of charred wood approximately 1-5mm thick in
localized areas of the lid.  The consolidant was required to be
flexible enough to withstand the likelihood of dissimilar seasonal
movement of undamaged, adjacent wood.  It also had to be compatible
with fill materials, additional hide glue adhesive and replacement
veneer.

I tested several resins including Butvar B-98, B-72, Aquazol and
several epoxies using various methods of application including
brushing, immersion and vacuum impregnation.  Samples were examined
with SEM to determine the depth and consistency  of penetration.  In
terms of strength and penetration, the most promising result was
from the epoxies.  In consideration of the properties and
requirements of the consolidant, I chose to use a product called
ConservEpoxy 100 flexible wood consolidant.  This epoxy had the
advantages of a 5 day cure time (allowing for maximum penetration)
and flexibility when fully cured.  The issue of irreversibility was
an obvious concern but in my opinion the advantages outweighed this
drawback.

The results for the other resins were not satisfactory for the
penetration and strength required and even a reversible resin would
likely prove difficult to remove in the future.

Charred areas were isolated with a wax dam, flooded with the resin
and impregnated under vacuum in a freeze dryer (to accomodate the
size of the lid) at room temperature. The ample working time of the
resin allowed for multiple cycles under vacuum and adequate time for
removal of excess resin.

Amanda Salmon
Furniture Laboratory
Canadian Conservation Institute


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                  Conservation DistList Instance 23:19
                 Distributed: Sunday, November 29, 2009
                       Message Id: cdl-23-19-007
                                  ***