Trees Need Lignin, We Don’t!

April 30, 2019

By Kathleen Daly


As museum professionals, we all understand the importance of using acid-free, archival materials. We also know the cost associated with buying these supplies from reputable vendors that are tried and true. It is important, however, for us to remain informed and diligent when making supply purchases. Nomenclature is often misused, which can lead to inadvertent confusion and misuse of budgeted dollars.

I was reminded of this after a recent purchase by the OHS museum collections department. After much research, we decided to purchase a pH testing pen. Like a child with a new box of markers, I began coloring on everything (well, storage materials only, of course!). The most surprising discovery came from our standard banker-style archival box. Sold as acid-free, the boxes clearly read as acidic when I applied the pH pen. In that moment, I realized that we had forgotten a fundamental aspect of what “acid-free” really means.

The Society of American Archivists’ website, with a little help from Richard Pearce-Moses’, A Glossary of Archival and Records Terminology, provided a brief review:  

  • Acid-free — A term loosely used for papers and other materials with a pH of 6.0 or greater. This term refers to acidity at time of manufacture.
  • Lignin-free — Material made with less than 1 percent lignin.
  • Lignin — An organic substance in plants that makes cell walls strong and rigid. When left in paper made from wood pulp, the paper will become acidic due to the lignin chemically degrading. Over time, this substance embrittles and browns.
  • Archival — Not causing degradation, or resistant to deterioration or loss of quality.

So, the most important question to ask when purchasing paper materials is, is this material lignin free? While vendors may label archival supplies might be sold as acid-free, it must only meet this standard at time of manufacture. If lignin is present, it will most definitely become acidic as the lignin breaks down. Unfortunately, some of our archival boxes were not lignin-free.

When making a purchase, don’t hesitate to ask what the product is made of. Initiate your own research, create your own tests (buy a pH pen!), and build your own a safe-vendors and supplies list. Archivists and collections staff alike must be the advocates for our historic collections and not simply use products just because they are “what we’ve always used.”

If you are interested in purchasing your own pH pen, a November 1990 paper published by Conservation OnLine (COOL) outlines the best on the market.

The Metropolitan Museum of Art is currently completing a study to test the archival quality of museum materials. This study is a much-needed asset for the field. In the meantime, access the American Institute for Conservation's (AIC) Wiki to review their materials database. The Canadian Conservation Institute also recently released Technical Bulletin 32, which provides general information on preventive conservation materials. Additionally, the National Park Service published two Conserve O Grams that should be posted nearby as your cheat sheets: Buffered and Unbuffered Storage Material, and Safe Plastics and Fabrics for Exhibit and Storage. Lastly, don't forget about your peers! The Oregon Heritage Commission and the Oregon Museums Association can help you reach out to others in the field.

Remember, be a conscientious shopper and investigate your materials. Ask questions and always ask for proof. And a good rule of thumb to follow: lignin is for trees, not museums!

Categories: Tips and TricksAudience(s): Industry Professionals

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