Substitute for Vinamul 3252

I was asked to post this for my friend, Mr. Colin Johnson, formerly
Ethnographic Conservator for the British Museum, London, who is now
in private conservation practice in the U.K, because he has not been
on the Internet since leaving the British Museum. I have been
inquiring on his behalf for any fellow conservation scientists who
have been doing research in this area, but without success to date.
However, I am hopeful that a Distlist Posting may bring us up to
date with current research.

    Vinamul3252 poly vinyl acetate/polyethylene copolymer stock
    solution is soluble in water and acetone. It is a 57% solids
    suspension in water: for practical purposes I regard this as
    100% or 'full strength'. Once set it is partially soluble in
    acetone.

    It has been used with great success for the past twenty years as
    an adhesive for the relaying of insecure and lifting applied
    surfaces, particularly on ancient Egyptian wooden coffins.
    Typically these may have a base layer of linen stuck onto the
    wood with animal glue or vegetable gum, followed by plaster
    (usually calcium carbonate with a similar medium) and finally
    the paint layer. I normally use a 12 or 6% solution in water
    with a preliminary application of either white spirit or IMS to
    act as a 'wetting' agent and encourage penetration of the
    adhesive solution into areas of blind access.

    The use of poly vinyl acetate adhesives in the conservation of
    cultural material is a matter of some controversy. The lack of
    stability that has been found in aging tests and sometimes
    observed in the studio has militated against their wider use.
    However, Vinamul3252 showed acceptably well in a range of tests
    and has been used ever since as described above. The tests
    included heat and light aging both of which gave a minimum of
    discolouring; a ph of approximately 6. and continued
    flexibility. The set adhesive is matt. The only real
    disadvantage being a reversibility of only something like 50% in
    acetone. Coffins which I conserved twenty years ago show no
    adverse effects from the Vinamul 3252.

    I am informed by friends at the BM (British Museum) that recent
    batches show browning of the stock solution and a tendency to
    stain original material (a great sin!). It is suspected that the
    formulation has been changed. Anyway, a substitute is required!

    The requirements are:

        *   A dispersion/emulsion that after setting is soluble in
            acetone or possibly IMS.
        *   Clear when set.
        *   Neutral, or near, ph
        *   Stable in light and heat aging tests.
        *   Matt when set

    When reduced to say 6-12% solution in water (the higher the
    solution percentage the more difficulty will be experienced with
    staining and alteration/enrichment of colours) remains a useful
    and efficient adhesive for the purpose of securing lifting
    applied surfaces.

    Colin Johnson
    Formerly Ethnographic Conservator, The British Museum, London.
    Currently a Conservator in Private Practice, Brentwood, Essex,
    UK.

Glennda Susan Marsh-Letts
1 Silva Road (Cnr. George and Silva)
Springwood, NSW, 2777
Australia
+61 2 47 513 013


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                  Conservation DistList Instance 16:69
                   Distributed: Tuesday, May 6, 2003
                       Message Id: cdl-16-69-010
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