Consolidants for dry archaeological organics

Ainslie Harrison <5ah38 [at] queensu__ca> writes

>We are interested in advice regarding a consolidant for extremely
>brittle and desiccated organic remains.  A bronze disk that was
>block lifted in Mongolia was brought back to our lab and micro
>excavated over several years to reveal a number of organic remains
>sitting on the surface of both sides including textile, horse hair,
>and desiccated leather. ...

My department at the Swiss National Museum works with dried as well
as waterlogged organics, these usually from the neolithic era.  My
specialty is textiles (usually of flax) and basketry (usually of oak
or linden bast). Often, we come up against delicate pieces that have
been through a drying process using the alcohol-ether method, in
which case the fibres are usually extremely fragile and aqueous
consolidants are not an option.  After much experimentation we've
narrowed our options as follows:

First, are your organic remains mineralized?  If they have been in
contact with copper alloy they may very well be.  If so, you can
proceed with Paraloid B-72 in toluene.

If your organic remains are not mineralized, then you must gauge
whether they are carbonized or uncarbonized.

If carbonized, we return to Paraloid B-72, a 2% solution in toluene
is often best but can go up to 5% if necessary. You might also try a
5% solution of methyl cellulose in 60% ethanol but only if necessary
for a strong bond.

If uncarbonized our non-aqueous solution is methyl cellulose in
ethanol as the consolidant.  After trying many different cellulose
ethers, we came back to Dow's Methocel A4C.  Two nebulizer quality
solutions would be 0.25% Methocel A4C in 60% ethanol or 0.4%
Methocel in 60% ethanol.  For stronger applications that 5.0%
solution of Methocel in ethanol as described above for carbonized
pieces can work well but is too thick for the nebulizer.  Use a
pipette but again, only if the fibres are robust enough to take it.
For preparing non-aqueous solutions of Methocel see Dow technical
handbook.

Leather is another thing altogether and would need advice from
someone other than myself.  We are grappling with both waterlogged
and desiccated stuff at the moment and I could let you know how it
turns out. Good luck,

Kim Travis
Konservatorin/Restauratorin
Schweizerische Nationalmuseen
Zentrum fur Konservierung
Lindenmoosstrasse 1
CH-8910 Affoltern a. Albis
Switzerland
+41 44 762 1376
Fax: +41 44 762 1361


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                  Conservation DistList Instance 22:35
                 Distributed: Monday, December 8, 2008
                       Message Id: cdl-22-35-007
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