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thanks to all for the clarifying details on my rather hasty statement about silk velvet.
Judith Andrewartha
Textile Conservator National Museum of Australia GPO Box 1901 Canberra, ACT 2601 Australia phone + 61 (0) 2 6208 5153
fax + 61 (0) 2 6208 5167 email j.andrewartha@xxxxxxxxxx >>> karin.vonlerber@xxxxxxxxxx 30/06/2005 4:41:42 pm >>> I am astonished silk would offgas sulfur. Where would the sulfur come from? From dyeing or from sizeing? Or could it be, you might have mixed that up with wool, where the polymers are interlinked with sulfur bonds? The only amino acids containing sulfur are cystine, cysteine and methionine, if I am not mistaken. Of these, only thwo amino acids are present in low concentrations in the amorphous regions of silk at an amount of 0.2% (cystine) and 0.1%(methionine) (c.f. A. Timar: Chemical principles of Textile Conservation, London 1998, p.43). Even with wool, you would have to strongly illuminate so as to liberate hydrogen sulfide from the molecular structure of wool (cf. Jean Tetrault "Airborne Pollutants in Museums, Galleries and Archives...." CCI, Ottwa 2003, p.11).
I would be very interested to know, if these small amounts of sulfur containing groups in silk have proved to cause degradation by liberating sulfur containing volatiles in any reasearch/test situations I might not be aware of. As far as MDF is concerned, I am not sure about precise levels of various compounds in the US, but in general your regulations are more strict than ours; therefore I dare making the following statement: long times ago, MDF offgased considerable amounts of formaldehyde and acetic acid. Nowadays - at least in Europe - this offgasing is below detection limit, if the boards are left in a well ventilated room for 2-4 weeks prior to use. Depending on risk evaluation (humidity will warp acidfree board, water damage can be deleterious with acidfree board, MDF might pose some risk if not properly sealed or if the wrong type is used, PE-type boards pose considerable problems in the context of fire....) MDF might be more or less appropriate than other materials. So, as always, it depends on each single case. Karin von Lerber -- Karin von Lerber Prevart GmbH Oberseenerstr. 93 CH-8405 Winterthur Tel. +41 (0)52-233 12 54 Fax. +41 (0)52-233 12 57 e-mail: karin.vonlerber@xxxxxxxxxx www.prevart.ch Jane Hammond schrieb: Thank you for the suggestions. I'm sure the objects conservator is not planning to use a product that would be so detrimental - perhaps I misunderstood, and I'll suggest an alternative. As for silk off-gassing, I should have thought of that myself rather than being so focused on being "historically accurate". Your reminder is well-taken and appreciated. |