condensation in plastic

[Jenny Barnett <andelos@xxxxxxxxxxxxxx>]

Dear Jerry,
A good one! Can we all agree never, ever again to use the term "breathe"
until it is proven beyond doubt that textile fibers have tiny lungs
(perhaps in the amorphous areas?)? Instead, "ventilate" perhaps, or
"porous to air and moisture", both rather clumsy. Any other suggestions?

The best analogy I have heard is the bread bag theory (as yet
unpublished) from paper scientists/conservators here in the Netherlands.
You know how if you let bagged bread lie in the sun, condensation will
form on the inside of the bag even though the RH has not changed. This
is due to the sudden rise in temperature which forces the fibers to
release the held moisture. The moisture may then, more or less, be
reabsorbed when the heat is lowered. The theory is that it is this
heating moment which causes the most fiber damage (sudden change in
tension). The tentative conclusion is that you can better control RH by
controlling temperature rather than trying to control or remove
moisture.

CCI are also propagating this idea I think, but I'm not sure: paper
given at 1987 ICOM meeting ??

The article by Stephen Hackney, Framing for conservation at the Tate
Gallery, The Conservator, nr. 14, UKIC,1990: is very good. And if you
can read Dutch, de Restaurator, nr. 2, 1995 has several articles on
research into the browning process of passe-partout cardboard which are
very relevant for framed and stored textiles and cellulose textiles. You
should be delighted to hear that these articles largely support your
understanding that the more the fabric "breathes", the faster it ages
and develops discoloring. As usual, outcomes depend on the
circumstances. I have always imagined this stress in terms of the fibers
frantically doing those exhausting star jump exercises as the moisture
comes and goes.

As for plastic storage materials and framing (as I understand it), if
the textile and atmosphere is "dry" at the moment of containment, then
the risk of condensation on the surface of the plastic/glass will be
reduced. The inclusion of moisture absorbent materials (flannel covered
A.F. card with framing; cellulose fabric or a.f. tissue in package) in
the package should reduce the risk further (so I have been taught). But
wait! these absorbent materials will also release moisture in the case
of heat, thus perhaps even increasing the degree of condensation!!! Has
anyone ever done research into this? Have I/we been laboring under a
myth?

In general, I think that it is choice between protection from outside
factors or inside factors. It is of great importance to understand all
the processes involved. Each situation will dictate different priorities
and therefore a different set of selection criteria for the best storage
/framing method/materials. One has to be willing and able to approach
each new situation as unique. This is of course more difficult and time
consuming than always using the same approach. But are we inquiring and
intelligent professionals or not?

At last, another meaty discussion topic. Thank you  Jerry. I hope that
no-one will reply privately because that would contradict the aims of
open discussion and the spreading of knowledge and ideas.

Jenny Barnett
Andelos Textielrestauratie
Oude Looiersstraat 65-67
1016 VH Amsterdam
NETHERLANDS
tel/fax 00 31 (0)20 427 18 27
andelos@xxxxxxxxxxxxxx