Watercolour on thin board

I am hoping to get feedback on options for treating watercolours on
very thin acidic board.

In our collection we have a number of works by an artist named
Marmaduke Matthews (1837-1913). Several of the paintings are on what
appears to be 1-2 mm thick 'Masonite' type boards.  If there is a
paper layer it is very thin and is hard to determine, as in most
cases the entire surface is covered with paint and the edges are
often damaged, however, I think the paintings are straight on the
boards.

The acidity of the boards has caused the colour to change
extensively and has affected the contrast of the images. They are
mostly mountain scenes that now appear very orange-brown overall.

My preliminary thought when I first started examining the pieces was
to mechanically remove the backings and to wash the works, where
possible. But further examination makes me concerned that:

    a.  the boards, likely, do not have paper layers and so are not
        'backing boards' per se, so I would be trying to thin the
        board as much as possible and then washing the remains--this
        feels risky especially if the boards do not have the
        cohesion of paper sheets.

    b.  the board is so brittle and stiff that it may crack while
        being worked on, there are corners and edges lost already,
        here and there.

    c.  I have thought about facing the painting to protect the
        board from cracking, and to bolster the paint layer, but
        there are areas of gum Arabic glazing--I worry that the
        shininess would be lost or damaged due to any adhesives
        being used on it.

Has anyone attempted this type of treatment? Are there any
suggestions for how to go about this process? Any ways to do it as
safely as possible? Would it be best just to leave the works as is
and accept that they are degrading quickly and are visually
distorted?

Ms. Lee Churchill
Paper Conservator
Glenbow Museum
130-9th Ave, S.E.
Calgary, AB T2G 0P3
403-268-4183
Fax: 403-265-9769


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                  Conservation DistList Instance 21:24
               Distributed: Saturday, September 29, 2007
                       Message Id: cdl-21-24-027
                                  ***