Sarah Lowengard is an art conservator who specialises in textiles. She kindly gave her permission to post this information for interested embroiderers. A link for further information is provided in the body of the text.
1. The blanket use of materials designated “acid-free” does not guarantee long-term safety. You must consider the composition of the fibers and the materials you use to store them. Most paper-based goods designated acid free were developed for works of art on paper. A common technique to protect this art is to buffer the storage materials — make them slightly alkaline, in an effort to mitigate the fact that as the material ages and becomes more acidic. These materials are fine for storing cotton or linen, which are chemically related to paper, and also tend to become more acidic with time. They are not that great for wools or silks, however, because they tend to become more alkaline as they age, and the raised pH of the storage materials might, under the right circumstances, hasten the deterioration of theose protein fibers.
2. Polyester films –aka mylar, but you have to be careful that it’s not coated with something that is potentially harmful –are generally accepted as non-destructive, chemically stable and safe for both protein-based (silk and wool) and cellulosic (linen, cotton, rayon) fibers. Unless you use only cotton and linen threads on only cotton and linen fabrics you might want to consider a storage system that takes advantage of the universal compatability of these plastic films.
3. You cannot realistically expect that you can get a straight answer out of the local fabric or craft shop about the nature of the storage materials they sell. You cannot tell simply by look or feel of materials whether they are safe, and the terms like “safe for storage” “archival quality” or “used in museums” are not controlled by any established standards. For a number of situations (including that special box your drycleaner might sell
you to store your wedding dress), paper goods might be simply sprayed with a de-acidifying solution and sold as “acid free.” The purpose of the local shops is to sell goods and I have found that many sell items they believe are safe that are in truth not good enough. This is not disingenuousness; the details of long-term preservation is more than you can expect them to know.
4. If you are interested in investigating storage materials that are made for the library museum industry, there are many reputable suppliers in the US. Three well-known, large firms are Light Impressions, University Products, and Gaylord. All have a web presence, and all have a customer service department that will answer your questions and can make recommendations. I believe all have information sheets or pamphlets about storage or care of materials that they distribute freely. If you want more information about museum concerns, procedures, and standards, as well as museum suppliers, there is a website located at Conservation OnLine (CoOL)
5. You have to face the fact that organic materials deteriorate in time and, although you can slow the damage you see, you cannot stop it.
6. Further, the craft industry assumes that materials will turn over or be abandoned fairly quickly . Again, there are no longevity standards for these goods. I doubt there ever will be, because it is too expensive to establish and implement them. This means you cannot ever be sure that your floss or embroidery cloth or whatever will last –but neither can you assume that it won’t.
Sarah Lowengard February, 1999 New York City