Watercolour on thin board

Lee Churchill <leec [at] glenbow__org> writes

>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 curious problem here is the dates for the artist. If he died in
1913 he may have painted on varieties of pressed wood fiber boards
like Masonite (which uses in this specific type of board Lignin as
the adhesive as Ian Batterham notes).  Some Masonite products were
produced with one side polished and waxed, the other retained the
mat impression from the manufacturing process. Heat and pressure
were used in the manufacture of these boards and, As Ian notes, they
contain considerable materials that led to degradation.  I once did
a series of experiments with Masonite by heating them in a microwave
and measuring the gaseous products and changes in the surface
textures.  There was quite a production.  I never quantified the
results, however.

I was amazed by the stability of such boads and the lack of
penetration to the surface of fractions one might expect over time
in painted surfaces. I have removed papers glued to surfaces from
art made in the 1940s and 1950s where a variety of adhesives were
used and neither the adhesives nor the paper seemed affected by the
ageing of the Masonite.  It would be interesting to do  a large
study of a number of paintings from that period today and see what
the condition was.  Usually, however, artists did paint directly on
the surface, with oils, synthetic media and sometimes with
watercolor and tempera.

The apparent contradiction with what Ian stated is that some
Masonite does have the untreated surface that can take water-based
adhesives and pigment, on the other hand, many boards were produced
by similar processes and were treated by artists and manufacturers
to take water-based pigments or adhesives, etc.

This is a subject for a dissertation or MA thesis.

Where studies have shown that particle boards are high emitters of
urea-formaldehyde (Science 80, March/April, p. 30 and 12th
Particleboard Proceedings 1978), Masonite as a patented process does
not use such adhesives.

Gettens and Stout, Painting Materials, 1942:223, discuss this
process and the threes general types produced with their varying
characteristics, including the hard tempered board.  As I mentioned
in the earlier comment, some Masonite like boards have a finished
wax surface, but the Masonite process involves high heat and
pressure combined with oils in some cases to produce different
surface features for construction use, etc.  Ann Brooke Craddock
prepared a paper on the subject of pressed boards and their
stability, and I believe she published it, though I no longer can
find a copy.  Ruheman, 1968, Keck, 1965 and1972 ed, Broustead, 1961,
Hulmer, 1971 and Wehte, 1965 and 1975 ed. all advise the use of
Masonite and similar products so it is not unusual to find them in
use by artists.  Weidner, 1967 did show some degradation examples of
boards in contact with particle boards, but not Masonite. The
Chemical Dictionary in 1977 listed patented elements of the Masonite
process as including an emulsion with a paraffin base.  My tests
showed that a brownish gas was released at temperatures above 100
deg. C, for less than 3 hours.

Niccolo Caldararo
Director and Chief Conservator
Conservation Art Service


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                  Conservation DistList Instance 21:31
               Distributed: Wednesday, November 21, 2007
                       Message Id: cdl-21-31-005
                                  ***