Thanks Mary and all the other writers,
I do enjoy reading about a good question....
As a textile quality instructor for Interior Design, I discuus the new
processing methods of fabrics and basically describe silk as weighted
so therefore it has heavy chemical use because of its basic nature. I
beieve the cut pile of silk velvet has less finishes and comparably
less toxins per ounce but we'll leave all of that testing up to Mary
and CAL.

I would like to go back to the original query where you said it would
be backed with ragboard and MDF.

There is a slight improvement over MDF called MDO, but they are both
excessively heavy. MDO has a baked on vinyl coating that is supposed to
be a formaldehyde barrier.  Because of glue toxins I always avoid any
semblance of wood, by using double corrugated grayboard from an
archival company. I line the board with cotton batting or cotton
flannel, then fabric, then the object. The cotton behind the fabric
should absorb most of the impurities within the environment.
Jennifer Hein
Indianapolis, IN Conservator
RE Silvercloth: I was told by chemist that the Pacific Silvercloth
needs to be in direct contact or have air pushed through it to absorb.
After all of the case contaminant problems we had at a large
institution I tested almost everything and found that in a closed
container I believe the most absorbent material is more beneficial for
fumes.
A short Case Materials quality listing is available if you wish.
[log in to unmask]

 "Modern acid dyes for silk are going to have sulphonic acid
substituents in order to make the dye soluble in water. I haven't heard
of these components being a problem for silver but you could interface
the silk with some sacrificial, absorbent like Pacifica cloth if you
suspected a source of sulfur contamination. Mary
>
> *bibliographic references see http://www.bcin.ca/Interface/bcin.cgi

--Jennifer Hein
Preservation Consultant
Historic Object Conservator of Textiles, Leather & Ethnography
PO Box 90379, Indianapolis, IN 46290
317-575-9296