Bronze paint on picture frames

Bronwyn Roberts <robertsbronwyn [at] hotmail__com> writes

>... I am researching the use of imitation gold leaf and
>bronze paint on 18th and 19th c. English picture frames.
>
>Although I am only in the initial stages of research, I wonder
>whether anyone knows of any references on the removal of oxidised
>bronze paint from oil or water gilding. I am also trying to find out
>whether there were specific kinds of bronze paint being used during
>these centuries and, more specifically, what binding media were used
>in these paints.

It is not clear whether you intend to focus your research on
materials and methods used originally to imitate gold leaf in the
18th and 19th century, or whether you would like to investigate
bronze paint used in overpaints? The best article I have read on the
varied materials used for centuries to imitate gilded surfaces is an
unpublished paper of Professor Jonathan Thornton, the Buffalo State
College, "All that glitters is not gold: other surfaces that appear
to be gilded", which, as I understand, is a written version of his
lecture delivered at the Gilded Metal Surfaces Symposium, St. Paul,
Minnesota, 1995.

In reference to bronze powders (the name is confusing, because as a
copper/zinc alloy, a proper name would be brass powders), Thornton
stated that metal powders are only reflective if they are in the
form of flat, shiny flakes, and this was accomplished by first
beating the metal into leaf and then grinding it into powder with
the aid of an organic medium such as honey or gum that prevents the
particles from sticking to each other. (The same method has been
employed for making genuine gold powder, which has often been
applied using water gilding technique for creation burnished
surfaces. M.S.)

According to the Thornton's article, a description of the ancient
technique of reducing gold leaf into gold powder was included in the
Theophilus treatise in the 12th century, who stated that a similar
method worked equally well for other metals. The technique involved
"a simple machine that operated by a strap winding and unwinding on
a shaft that turned a bronze pestle in a bronze mortar". Until 19th
century the laborious process of making bronze powders was
distinctive for German manufacturers, particularly of the Nuremberg
(Nurnberg? M.S.) region (well established brass industry), and was
rather expensive, and therefore restricted for use on high quality
objects.

Thornton mentioned that in 18th century there were some English
makers as well, including "Mr Warren of Birmingham", but the real
breakthrough was the invention of the mechanized process of
manufacturing of bronze powder by Bessemer in Nuremberg. After
intense research, Bessemer began manufacturing and marketing of
bronze powders in about 1840 at much cheaper prices. He developed "a
gold paint" devising a medium, which he stated "would preserve the
gold colour for as long as possible". According to Thornton, an
extensive use of "gold powders" was economically untenable prior to
Bessemer?s invention.

I would recommend contacting Professor Jonathan Thornton in order to
obtain the entire article and get more advice on this subject. I
hope Jonathan will forgive me for allowing myself to provide his
address here;

    Professor Jonathan Thornton
    Art Conservation Department
    Buffalo State College
    Rockwell Hall 230
    1300 Elmwood Avenue
    Buffalo NY 14222-1095
    716-878-5029
    Fax: 716-878-5039
    fundi [at] buffnet__net

In regards to removal bronze overpaintings from gilded surfaces I
would refer you to several papers related to this subject included
in:

    Bigelow, D., Cornu, E., Landrey, G. J., Van Horne, C.,  (editors),
    Gilded Wood: Conservation and History, Sound View Press,
    Madison, Connecticut, 217-228 (1991)

    Budden,  S.,  (editor)
    Gilding and Surface Decoration. Preprints of the UKIC Conference
    Restoration '91, UKIC (1991)

    Dorge,  V.,  Howlett,  F.C.
    Painted  Wood:  History  and Conservation, Proceedings  of  a
    Symposium  organised  by  the  Wooden Artifacts Group of the
    American  Institute  for  Conservation  of  Historic  and
    Artistic Works and the Foundation   of   the   AIC,  held  at
    the  Colonial  Williamsburg  Foundation, Williamsburg, Virginia,
    11-14 November 1994, The Getty Conservation Institute, Los
    Angeles, 514-527 (1984)

    Mills,  John  S.,  Smith,  Perry  (editors)
    Cleaning, Retouching and Coatings, Technology  and  Practice for
    Easel  Paintings  and  Polychrome Sculpture, IIC preprints  of
    the  Contributions  to the Brussels Congress, 3-7 September
    1990, London,  The  International  Institute for Conservation of
    Historic and Artistic Works (1990).

Removal  of bronze overpaints from gilded surfaces has also been
covered to some degree in the following publications:

    Moyer, Cynthia, and Hanlon, Gordon
    Conservation of the Darnault Mirror: An Acrylic Emulsions
    Compensation System, JAIC 35, 1996, 185-96

    Sawicki, M.  (1995)
    Picture Frame Conservation or "Repairing", AICCM Buletin, vol.
    20, No 2.

    Sawicki, M.  (1999)
    Caring  For  Your  Gilded  Picture  Frame
    in: Frames, Melbourne Journal of  Technical Studies in Art, Vol
    1, The University of Melbourne Conservation Services, 147-156.

    Sawicki,  m., (forthcoming)
    'The Visit of the Queen of Sheba to King Solomon' by
    Edward Poynter, 1884-1890. The frame revisited.
    in: AICCM Bulletin.

This list is obviously incomplete, and can be extended by other
publications related to gilded/polychrome objects conservation,
including furniture, frames, altars, sculptures, icons, paintings on
wooden support, etc. I would suggest searching CHIN for other
titles.

We have not yet conducted systematic methodical research on mediums
used in bronze overpaintings, but from our experience in the
conservation of gilded surfaces at the Art Gallery of New South
Wales, the mediums in bronze overpaints can include: shellac and
other natural resins, oil, cellulose-nitrate based lacquers, and
other synthetic polymers based lacquers (polyurethane, acrylics,
etc.).

In the first few decades of the 20th century bronze powders were
also popular for the creation of burnished surfaces, using
water-gilding technique, in a similar manner as with genuine gold
powder. These original surfaces could be oxidised, but should not be
confused with bronze overpaints.

I hope that the above information will help you a little bit with
your investigation. I would be very interested in the outcome of
your research and would appreciate it if you could send me a copy of
the final draft of your paper.

Malgorzata Sawicki
Head of Frame Conservation
The Art Gallery of NSW
Art Gallery Road
Sydney NSW 2000
Australia


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                  Conservation DistList Instance 13:46
                  Distributed: Tuesday, March 7, 2000
                       Message Id: cdl-13-46-002
                                  ***