Hello all, I've got some acid-free tissue that's been giving me some odd, fluctuating pH readings, and a paper conservator suggested I reach out to you.
I'm working on a hat and shoe rehousing project and ordered a roll of unbuffered, acid-free tissue from Gaylord. After I was partway through the project, I tested the tissue with a Lineco pH pen which shows purple for materials 6.8 pH and above and yellow for other, more acidic values. It was yellow, so I contacted Gaylord and they sent me another roll from the same batch that they had marked and found to be purple. The roll sat in its box in my office for about a week before I opened it. The mark that they had put on top was still purple and pieces that I tore off the edge and tested with my pen were also purple. (It's worth noting that the pen seems to mark things properly in other cases, from acid-free file folders to pieces of modern [acid-free] printer paper, to acidic cardboard boxes.) The roll sat in my office out of the box for about another week, maybe a week and a half. At that point, I noticed that the purple mark they had made on the top of the roll was yellowing, the pieces I had torn off and marked before were now yellow, and new pieces that I tore off and marked were yellow. My office doubles as our rare book room, so there are a lot of acidic materials in the area, though none have been in physical contact with the paper. Much of this happened in July in Minnesota, so the temperature was controlled, but the humidity fluctuated and was higher than average. There is a piece of printer paper in my office that I marked a month previous, which was purple and the color has not changed since. Buffered file folders and unbuffered document boxes in the room have also not changed from purple in the past month. We moved the roll into our Collections Storage Room, which is temperature and humidity controlled, a few weeks ago. I just looked at the roll and the line Gaylord drew on top is mostly purple. I drew several new lines on top and they are very purple. I recently retested the roll, which has remained in our CSR. The marks on top are still distinctly purplish, as were new lines that I drew. They are not a bright purple, but they are also definitely not yellow. I tore off a new piece and tested it. It was yellow, but in the places where I went over it several times, it took on a purplish hue. Now, after several days, it is definitively yellow. I'm wondering if any of you have ever seen this before. Is the paper actually changing pH? Is it just the pen reading changing? Is there something wrong with my pen? With my paper? Is this going to harm my collections? Is this a problem with all acid-free tissue, just with Gaylord's, or just this batch? Any and all advice and knowledge is welcome. Thanks, Amanda -- Amanda Roberts Curator Rice County Historical Society 1814 2nd Ave NW Faribault, MN 55021 507-332-2121 rchistory.org ****** Unsubscribe by sending a message to consdistlist-le...@cool.conservation-us.org Searchable archives: http://cool.conservation-us.org/byform/mailing-lists/cdl/
