Consolidant

Claire Daly <claire_daly [at] birmingham__gov__uk> writes

>I am to conserve a large panel with applied "Grinling Gibbons"
>carvings, which has suffered from severe Furniture Beetle
>infestation.  After Thermo Lignum treatment, I need to consolidate
>the flight holes.  Does anybody have experience of consolidating
>Gibbons carvings, or can anybody recommend a suitable consolidant,
>which will give sufficient depth of penetration and also avoid
>swelling the wood fibres?  Paraloid B72 in acetone has been
>suggested, but I am interested in alternatives.

One possibility I have used very successfully follows the research
of the late Morgan Phillips of SPNEA, Boston (now Historic New
England). This employs as consolidant a combination of the acrylic
monomer resins, methyl acrylate and ethyl methacrylate. At room
temperature, these are fairly thin liquids, and an oxidant such as
Percadox and application of mild heat must be added to the solution
before application in order to promote polymerization.

This is particularly effective for wood with severe insect damage,
weakening and loss. It fills cell walls, but does not fill voids, so
you entirely eliminate the "plasticy" appearance of most resin
consolidants. In fact, it is virtually invisible after it sets up.

On large planks like table tops, I have used electric heat blankets
(industrial, like the kind used to melt ice on roofs in winter) with
a thermostat and insulation. On small areas, I apply Saran Wrap
(polyvinylidene), the pour warm sand over the area to which
consolidant has been added. A temperature of about 105 deg. F for
several hours is suitable.

A significant disadvantage is that it is not reversible--the final
result is essentially Plexiglas or Perspex. But as noted, it is
virtually invisible, and results in no significant darkening or
change in appearance.

Immediately after removal of the heat blanket or warm sand, if
polymerized residues remain in some areas on the surface, these can
be wiped away with acetone--but you must do it quickly before full
polymerization occurs.

Another disadvantage--Percadox and similar oxidants are explosive,
and very expensive to ship, and dangerous to have around and store.
It is for this reason I have largely discontinued use of this
method. But under certain circumstances where the wood is severely
damage, significant strengthening is required, and reversibility is
not paramount, nothing I've found gives better results.

Robert Mussey
Robert Mussey Associates, Boston, MA, USA
617-364-4054


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                  Conservation DistList Instance 20:1
                  Distributed: Saturday, June 24, 2006
                        Message Id: cdl-20-1-011
                                  ***