Decorative painted surfaces on metal

Cynthia Jane Gorman <lu_who [at] hotmail__com> writes

>I am a MA student of Metals Conservation working on my dissertation.
>I just started to carry out a study of painted metal surfaces. ...
>...
>... I am looking for and would greatly
>appreciate any insights, leads to references, articles, books, and
>contacts about conservation solutions and techniques used for
>objects with paint on metal.

I recently assisted a private owner to conserve an advertisement for
Diamond Dyes of Pennsylvania that was fixed to a piece of shop
display furniture he was restoring. The advertisement was made up in
the following way: a flexible rolled sheet steel support measuring
about 40 x 60cm; a ground layer of white or cream paint; an image
layer of paint, made up of four colours plus black, which appeared
to be printed as it contained much subtle detail; and a final layer
of clear protective resin. Although the image was Victorian or
Edwardian in style, the thin flexible rolled sheet steel support
indicated that the advertisement could be a more modern
reproduction, but this was not investigated further.

The advertisement had been exposed to damp conditions for many years
and the steel had corroded under the paint, causing both general
staining and severe damage and loss in some areas. In addition, the
clear protective layer suffered extensive bloom, hiding the image
below. Solvent tests indicated that the paint layers were stable in
water and white spirit, but were soluble in other common solvents
such as acetone, IMS, and xylene.

Various avenues for cleaning were explored, with Aquabat, a
commercial product designed for cleaning nuclear power
installations, considered the most likely material to be successful.
This product was used to clean parts of an historic motorcycle which
combined plated steel and rubber parts, as reported in a recent UKIC
Conservation News (Cane et al). Unfortunately a sample of Aquabat
could not be obtained. The use of other chelating agents was
considered, as work had been done at the Museum of London on their
use in removing iron staining from vitrified enamel advertisements,
but this would have required considerable experimentation.
Eventually, after testing a small area, it was decided to treat the
advertisement with Biox gel, a gentle commercial rust remover. The
Biox gel was diluted with deionised water and the resulting slurry
was frequently agitated to ensure the mixing of the solution as it
chelated the iron from the paint layers. Over several hours the
design gradually became clearer as staining was removed, and areas
of gross corrosion were reduced to reveal the less obtrusive steel
below.

Due to time constraints, the Biox gel was rinsed away before removal
of all staining was complete, as it was considered by the owner that
an acceptable result had been achieved. After several rinses in warm
deionised water, the advertisement was gently dried with tissue and
placed in a fan-assisted oven at 30C overnight to ensure rapid and
complete drying. The surface was consolidated and protected with
Paraloid B67 in white spirit. It was found that the addition of a
little acetone to the B67 solution reduced the remaining bloom in
the old varnish layer and helped to reveal the painted image.

Will Murray
Artefacts Conservator


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                  Conservation DistList Instance 18:44
                 Distributed: Wednesday, March 16, 2005
                       Message Id: cdl-18-44-005
                                  ***