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Re: Acid-free materials sold in stores



Susan,

I get a lot of questions about these "acid-free" materials too.  They're
everywhere you look now, and often more convenient and less expensive than
the materials available from archival supply catalogs.  What I have to tell
people is that we just can't know for sure if they're okay.  They may be of
good quality, maybe not.  The only way to know for sure is to get exact
specifications on the product, including what type of fiber it is, what kind
of buffering agent was used and what kinds of additives were used (bleaches,
sizings, coatings, etc.)

A material can be called "acid-free" if it had a pH of 7 or higher at the
time it was made.  If it's made of poor quality materials, it may not remain
"acid-free" for long.  The manufacturer can use poor quality wood pulp and
unstable additives, but add a buffer to the mix to bump up the pH above 7,
making it "acid-free" temporarily.  The paper components can then degrade
over time and acids can be produced by the additives and the lignin in the
wood pulp, "overpowering" the buffer that was added to the paper and making
the paper acidic.

Most people don't want to go to the trouble of contacting the manufacturer
for specifications on various products, so my advice is usually for people
to buy "archival" materials from reputable companies that have demonstrated
that they understand and address preservation concerns.

Sandy Hempe
Conservator
Missouri State Archives

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