Waterlogged leather

Maria Grammatou <mgrammat403 [at] yahoo__com> writes

>We have found a piece of waterlogged leather together with copper
>coins, obviously it must have been a small leather bag. The biggest
>fragment is of the size of a thump and it carries some small coins.
>There is not enough leather to experiment various treatments. Which
>would be the safest procedure somoone could follow so as to preserve
>it? Maybe a PEG would be suitable, but which one would be best? The
>literature is a bit scary always mentioning procedures that fail and
>succeed even for different pieces of the same object. Any help will
>be appreciated.

Instead of PEG I would use Glycerol, since the latter leaves the
leather more flexible than the former. A solution of 20-30% v/v,
depending on the condition of your pieces, should be sufficient.
There are also other things, in such a treatment, to consider apart
from the lubricant. Since the leather pieces were found together
with copper coins it is most possible that they would be
"contaminated" with copper salts/corrosion products. In order for
any lubricant to work you would need to remove these first. That can
be achieved by using a sequestering agent, such as EDTA.

Also you would need to consider the drying method after lubrication.
The safest would be freeze-drying, but I am assuming that you
wouldn't probably have a freeze-dryer in your lab. Other
alternatives would be solvent drying (either ethanol or acetone) or
controlled environment drying with silica gel, where you gradually
lower the RH level.

A good, although old, article for such case is:

    Ganiaris, H. et al.
    (1982) A Comparison of some treatments for excavated leather.
    In: The Conservator 6. UKIC. 12-23.

Konstantina Tsatsouli, MSc
Conservator
13th Ephorate of Prehistoric and Classical Antiquities
Archaeological Museum of Volos


                                  ***
                  Conservation DistList Instance 22:30
                Distributed: Tuesday, November 25, 2008
                       Message Id: cdl-22-30-001
                                  ***