Cellulose ethers

Sent by Charles Davis, Bodleian Conservation on behalf of Alison
McKay who is one of our conservators.

    I am investigating cellulose ethers for use in our Library
    Conservation Section and need some advice. I originally wanted
    to write to R.L. Feller having read his "Evaluation of cellulose
    ethers for conservation",  published by the Getty Conservation
    Institute, Research in Conservation 3, 1990, but I suspect he
    has retired by now and I do not have his address.  So I am
    hoping that somebody out there will be able to help me or will
    know somebody who can.

    Over the last few years we have been doing less extensive
    treatments on manuscript and printed books. Where in the past,
    we might have disbound, washed and deacidified a volume, now we
    will often repair in situ. As a result we have done more local,
    in situ sizing on weak or soft paper in bound volumes. Because
    of doubts about the long term stability of hydroxypropyl
    celluloses we currently use  % w/v solution of methyl cellulose
    in 85:15 IMS (ethanol):water. This works very well as the % of
    water is low enough to avoid staining and distortion of the
    paper. The methyl cellulose we use is  high substitution from
    BDH (now Merck) a British chemical company. As our supply is
    running low and the company no longer supplies it, I am now
    looking for a replacement.

    Our ideal requirements are :

        1.  A product with excellent long term stability 2. A
            product which will dissolve easily in IMS  (which has
            low toxicity and thus can be used at the bench without
            special precautions)

    Our present methyl cellulose is not fully satisfactory on the
    second count  as it does not dissolve in IMS and I have found
    that to get the maximum % we have to dissolve  it first in 40:60
    IMS: water and then further dilute it with IMS: a laborious
    process.

    Having read of its excellent stability in  "Evaluation of
    Cellulose Ethers for Conservation", I am keen to find a high
    substitution methyl cellulose rather than another cellulose
    ether as a replacement . The companies I have approached (Dow,
    Aqualon/ Hercules and Courtauld ) do not seem to supply methyl
    cellulose with a higher  DS than 2.0. Having explained  my
    intended use, they have sent me samples of hydroxypropyl methyl
    cellulose: specifically Methocel 311 and Culminal  MHPC 20000S.
    The former has DS 2.0 with 25% methoxyl groups, 25%
    hydroxypropyl groups (quoted in their literature). I am
    concerned that the higher % of  HP groups (than for example the
    Methocel E tested in the report) will affect long term
    stability.  So I am asking for help with the following
    questions:

        1.  Has any testing been done on different HPMCs since the
            Getty report?

        2.  Is there an other product which would be suitable for
            our purpose?

        3.  Why cant I obtain a really high DS methyl cellulose?!

    In the absence of any research done elsewhere, I will assess the
    above products and perhaps one or two others by thermal ageing
    as outlined in the report, but I don't want to reinvent the wheel
    and I am sure other people must be in the same situation. Any
    help or advice  anyone can offer would be immensely appreciated.

    Thank you in advance,

    Alison McKay
    Conservator
    Bodleian Library Preservation & Conservation Division
    +44 2 77222

Charles Davis

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                  Conservation DistList Instance 10:39
                Distributed: Wednesday, October 16, 1996
                       Message Id: cdl-10-39-009
                                  ***