Cleaning silk

    **** Moderator's comments: The following appeared in Texcons-l

What should be used to wash silk? Modern/antique silk? Is it true
that Orvus (sodium lauryl sulfate buffered to pH7) is not suitable
for silk?

There are several factors associated with wet cleaning or washing
silk: the fiber, the yarn, the construction, etc.; the type of dye
and finish; the type of degradation of the silk; the type of soiling
or problem that one desires to remove (your goal).

1.  Fiber/yarn--many modern silks, especially garments are "dupioni"
    or spun silks which are made from short(!) silk fiber and do not
    have the same strength/characteristics as the monofilament
    fiber. The spun silks may be strengthened by water-soluble
    finishes (sizes, etc) so washing will change the handle and may
    be ill-advised.

2.  Know this or knowing the limited use of silk garments like
    evening gowns, manufacturers may dye with dyes which are not
    entirely substantive to the fiber. And, to be fair to
    manufacturers, silk is usually dyed at a lower temperature than
    wool even though the same dyes may be used; the fiber has a
    smaller diameters, etc. Wet-cleaning may not be advisable.

3.  Silk is weakened in water but silk may have already been
    significantly weakened by light (1000 hours sunlight in Welyn
    [sp?] Gardens, England reduced tensile strength by about 50%).
    Perspiration stains are acidic but components may induce
    fungal/bacterial damage leading to an alkaline condition; alkali
    tenders (weakens) silk. Wet-cleaning may not be advisable.

4.  Alkaline anionic surfactants (like commercial detergents or
    tensides) may damage silks. Soaps (also alkaline and anionic)
    tend to be adsorbed into the fiber, giving a soft hand.
    Sometimes the adsorbed soap residues off-gas. Neutral
    surfactants like "Orvus" can also be adsorbed. Non-ionic
    surfactants are adsorbed less, but may leave the silk with a
    harsher (by comparison) hand or feel. Anionics are better
    degreasing agents--cleaners--than non-ionics. Non-ionics are
    more likely to have redeposition problems, so the formulations
    are somewhat different than with anionics.

Depending upon one's goal, the type of soil, age/type of silk, there
are ways to mitigate or guard against some of these problems and to
wet-clean or wash silk. Perhaps that is what you are interested in?
Methods of support, logistics of wet cleaning?

Does anyone want to comment on "sand-washed" silk? Its durability
for washing?

                                  ***
                  Conservation DistList Instance 11:89
                   Distributed: Tuesday, May 5, 1998
                       Message Id: cdl-11-89-011
                                  ***