Linen thread

Following up some correspondence in Paper Conservation News, I wrote
the following to Bill Minter which could be of wider interest:

    I have only just got round to reading your article in PCN about
    this and Philip Sykas' response. The whole subject of linen is a
    tangled skein (sorry, I couldn't resist!) of misinformation and
    I would have to say that in terms of linen paper, renowned
    conservators (not you) have often got the wrong end of the
    thread.

    I do not have the files to hand nor the time to dig them out so
    the following is based on recollection of our research when
    developing and making our Renaissance linen paper.

    Flax growing and processing is a very complex commodity
    business. We had a lot of help from Jan van Gompel who runs a
    large merchanting company called

        Procotex of Henleykaai
        96 9000 Gent, Belgium
        +32 9 223 6436
        Fax: +32 9 224 0240

    We have been out of contact for over five years so this address
    may be out of date. However I found a web site through which you
    could track them and a lot of other linen info:
    <URL:http://www.textileaffair.com/Elin.html>.

    Procotex buy flax from over 80 countries and sell to 180. The
    biggest grower is Russia. Others include China, Poland,
    Netherlands, Belgium, France, Chile etc. It sounds very unlikely
    that poorer countries would use oxalic acid when water is free.
    But how could you tell (except by testing)?

    With Jan, I visited farms and processing plants in the
    Netherlands. This was about 1982 when there was still a little
    dew retting. The majority of processing then was by hot water
    retting. This was a relatively controlled process compared with
    traditional water retting where the bundles are just chucked in
    a ditch. Essentially the fibre was put in very large (say 10 x
    10 x 3 metre) concrete tanks of water heated to about 40-50o C.
    The heating speeded up the process. Whilst retting is
    potentially uncontrolled, the old craftspeople knew how to
    regulate these things. Hence mummy wrappers surviving 4000
    years. Poor control would reduce quality immediately and hence
    cut the price. It seems rather unlikely that fibre which was
    strong when sold would contain anything biological that speeded
    up its degradation with time (and in any case fungal spores are
    everywhere so infection is not really needed if conditions later
    became right). Furthermore the bacteria, fungi and enzymes that
    both produce are attuned to the non-cellulose components which
    contain much more nutrition than the cellulose. Most enzymes are
    very specific and indeed the paper industry has spent years and
    megabucks developing lignases for use in paper pulping. Residual
    retting bacteria/fungi/enzymes would have little effect on
    cellulose whereas cellulases (ie cellulose digesting enzymes)
    would but I am not sure if they would occur. Jan told me that
    the main factor in retting was a fungus that grows on the stalk
    of the flax as it grows. He did not mention bacteria which I
    would have thought would develop as a secondary process on the
    fungus/enzyme by-products.

    My organic chemistry is way out of  date but I would have
    thought that oxalic acid could react with cellulose and that the
    modified cellulose would remain if the oxalic acid evaporated.
    Whether this would be harmful or not I don't know and, unless it
    has been researched, I wonder if anyone does.

    The flax industry produces two main product groups. Linen is
    very long fibred (essentially the length of the plant) whilst
    flax tow is the shorter fibre which is used in a separate
    textile industry. Raw scutched linen is traded around the world
    in bales of several 100 kg. It is a commodity and it would be
    very difficult to track its provenance back unless you grew
    it--and then you might not be very good at it (in commercial
    terms). The next operator cards and combs the linen into sliver
    which is a regulated strip with all fibre running the same way
    and a few inches wide by a quarter inch thick. This is then
    roved which converts the sliver to a more or less circular
    continuous strand of  hundreds of fibres maybe 2 mm in diameter
    overall with a very slight twist in it. This is wound on
    bobbins. These bobbins are put on the spinning machine and spun
    to thread. There are integrated mills but also specialists do
    individual stages.

    My understanding is that bleaching is usually done on spun
    thread, but sometimes on rovings. I have seen bleached, combed
    but unroved fibre but understand this is rare.

    A large proportion of so-called "unbleached" thread is as you
    found bleached and then stained. Worse it is often stained with
    "iron liquor"--thought to be ferrous sulphate solution which
    sounds very bad news.

    So to be on the safe side you need to track back up the chain as
    far as you can, test the fibre and then have it spun to order.
    It should be possible to test for by products from bleaching,
    oxalic acid etc but this would be costly.

    So far as testing thread is concerned the textile industry uses
    the same basic tensile testing machinery as for paper, steel
    chains and concrete pillars. Plenty of people could do it at a
    cost. Whilst the inclusion of knots and kettle stitches may add
    realism, they would concentrate forces on to small areas in an
    unpredictable way (however much you standardised the procedure)
    and should be avoided.

    I hope this helps but fear you have some way to go and there
    needs to be a research grant to someone to sort it out. I assume
    that you have discussed with textile conservators but suspect
    they would prefer a thread which was less strong than the
    artefact so the repair failed before the artefact.

Simon Barcham Green

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                  Conservation DistList Instance 12:58
                 Distributed: Friday, January 15, 1999
                       Message Id: cdl-12-58-007
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