Catherine wrote: I have several old paper photos that date between the late 1860s and the early 1900s. I am worried about how to store these. Is it o.k. to put these in a plastic zip-loc bag or are there other alternatives.
You’re right to question the use of ordinary plastic bags. They are not suitable for long-term storage of photographs. For instance, Hollinger Corporation sells a wide variety of non-pvc sleeves and storage materials for pictures.
I’ve written several online articles on photographic storage and preservation. For additional information read “Four Destructive Habits”.