“People often ask how safe glue sticks are. Since there are many brands, and the formulations are likely to change without notice, it is hard to generalize. Individual brands have been tested to answer specific questions, but there has been no research that applies to all glue sticks. However, there was a short discussion on them on the Conservation DistList earlier this month, in which people shared their experience and observations.

In summary, glue sticks are said to be safer because they were less acidic, though some might be questionable in terms of reversibility. Also, all of them were said to harden up to the consistency of candy or shellac; wheat or rice starch paste was recommended instead. Another person recommended using a plastic syringe filled with “the adhesive of your choice.” They are as convenient as a glue stick and will keep the adhesive from drying out for as long as a year; a source is The Woodworkers’ Store, 21801 Industrial Boulevard, Rogers, MN 55374 (800/279-4441).

Jane Down’s message said that CCI [Canadian Conservation Institute] had analyzed three types of glue sticks in 1982 and found that they were all composed of poly(vinyl pyrrolidone) and had a pH of 9. The pH might be a problem with alkaline sensitive items. Labels glued 10 years ago peel extremely easily today and photographs glued at the same time lost their gloss in areas where the adhesive was on the reverse.”