You might know the importance of a protective enclosure, but how often to you consider the quality of storage materials?  In fact, the composition of storage materials plays a significant role in the preservation of archival collections.  But how?
Since storage plays a passive role, the positive and negative interactions of storage materials may not be readily apparent.  Chemical reactions that occur between library and storage materials are often a slow process, spanning over a number of months or years before a visual change occurs.  Without the gratification of seeing immediate effects, many may not realize how some storage materials can be problematic, let alone the ramifications for using non-archival materials.

 
To illustrate some of the effects, I thought I’d share a vivid example of protection from acidic materials during storage. The following photograph shows the positive effects of archival buffering paper (also known as interleaving), as well as the danger of using non-archival boards and tapes – even when they are not in direct contact with the object!
The protected object is a 17^th century printed broadside.  It’s a single sheet of paper with printed black text on the front.  The broadside was stored for many years in a green cloth-covered portfolio.

Within the portfolio, the broadside was secured beneath with folded sheets of plastic film with a blank sheet of paper.  You can see the plastic film is attached to the portfolio around the edges with green tape.

This image shows the front of the blank sheet of paper stored side the plastic film, below the broadside. The plastic has yellowed overtime.

Here, the blank sheet is removed, revealing yellowish-brown discoloration around the top and right edge. This discoloration aligns perfectly with the green tape that is adhered on top of the plastic –located on the top and right side of the plastic.

When you flip the paper over, the back of the blank sheet shows even more discoloration. In fact, the discoloration is a mirror image of the materials below the plastic! This has occurred because the plastic is “breathable.” The materials below are all acidic, except for the white fragments of paper, which protected a portion of the paper from turning brown.

1. Acts as a support for the broadside when handled.
2. The interleaving served as a sacrificial barrier that absorbed the bulk of acidic off-gassing from the non-archival paper and tape.

In summary, this enclosure is an excellent example of how different materials can interact with one another in nuanced ways, and how plastic is actually a permeable barrier to gasses overtime!
General storage tips:

• When placing interleaving within an archival polyester L-sleeve, make sure the interleaving tissue is larger than the object so you can avoid localized discoloration
• Architectural prints, blue prints and some photographs are special. Don’t store these in buffered materials (materials that are above pH 7).  Store them with pH neutral materials like polyester film or unbuffered paper.
• Check out these resources on selecting archival storage materials:
  • Connecting to Collections’ Collections Care Basics: Where Do I Begin?
  • National Park Service :
    • Buffered or unbuffered?
    • Blue prints and cyanotypes
  • Canadian Conservation Institute (CCI notes):
    • Black and white photographs
    • Color photographs
  • Sources for purchasing archival materials:
    • Conservation Resources International
    • Gaylord
    • Hollinger Metal Edge
    • Talas
    • University Products

Ashleigh Ferguson Schieszer (PLCH) —- Book and Paper Conservator