-----Original Message-----
From: Marconi, Emanuele
Sent: Tuesday, September 08, 2015 10:34 AM
To: [log in to unmask]
Subject: [MUSEUM-L] non acid-free paper for temporary use
[snip]
> The paper I tested has a Ph of 5.5 and should be used to wrap some wooden and metal objects for no
> more than 10 days, and the
> environmental parameters will be quite stable.
> Long-term use is highly not recommended for the reasons we all know, but someone of you has any
> experience in short-term use?
[snip]
A pH of 5.5 is natural for paper. Many studies of good quality older paper (100-300 yrs.) have
shown that this is an common pH for papers made of good quality materials. This means cotton or
bast fibers (flax hemp etc.). Alpha wood pulp, meaning processed, bleached and de-lignified wood
pulp that has a pH of 5.5 could be OK, certainly for 10 days, see exceptions below. And certainly
for up to 180 days, or so, if the paper has no lignin and the processing chemicals (sulfide
releasing materials) have been sufficiently washed before the pulp was formed into a sheet. The
easiest test is the photographic activity test.
But for 10 days this is overkill by a wide margin, see exception below.
However! If the materials you are working with are already highly degraded they need the good
influence of buffer tissue, or other buffered papers. They will have a pH ranging from 7.0 to 9.2,
or so. Calcium carbonate, the buffer material, has a natural pH of around 9.4-9.5. If added in
excess to paper, that paper can have a cold extraction pH up to about 9.45. Note that this highly
buffered paper is not recommended for photographic materials or those artifacts suspected containing
blue dyes; its surface is also quite abrasive.
Highly polished metals, e.g., silver, mirror-finish-iron and polished copper-containing metals, can
react quickly to any paper containing excess sulfites/sulfates, which are commonly used in
papermaking from wood sources. It the sulfur. it reacts to form black silver sulfide, iron sulfide
or copper sulfide. The Photographic Activity Test was designed for this application.
Tim Vitale
Paper & Photographs Conservator
Vitale Art Conservation
2407 Telegraph Ave
Suite 312
Oakland, CA 94612
510-594-8277
http://vitaleartconservation.com/
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