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Re: [BKARTS] "Archival" tissue paper

Any pH indicator, including the pen you are using, has its own intrinsic pH (essentially the pH of the ink before it touches anything), and if the paper is unbuffered the pH of the ink will dominate, so the indication isn't necessarily that the paper is acidic, but only that it has insufficient alkaline reserve to turn the ink purple.

It is possible to make a pH test pen which has a reverse reading: it changes colour if the paper is acidic (instead of safely neutral). This pen's ink would be intrinsically a little more alkaline, and a colour change would more conclusively indicate that the paper has become acidic. Different pen manufacturers use different ink formulations and these may yield different results for the same paper.

In the past year or so I saw an article comparing various brands of pH test pens, but now I can't remember where it was.
-Kevin Martin
 the Papertrail

> -----Original Message-----
> From: Book_Arts-L [mailto:BOOK_ARTS-L@xxxxxxxxxxxxxxxx] On Behalf Of Jane Thompson
> We found a roll of "archival" tissue paper purchased about
> ten years ago which, when tested with an Abbey pen, indicated
> a high level of acidity throughout.  This unscientific
> conclusion of a high level of acidity was based on the fact
> that the mark made by the Abbey pen did not turn purple.  We
> then investigated the tissue in use with our museum items and
> found that it, too, failed to turn the Abbey "ink" purple.
> Obviously, we have not taken coursework in paper chemistry.

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