Mass Deacidification

Deacidification is a process developed to neutralize the acidity found in modern, machine-made papers. Machine-made paper from about the 1850s through the 1960s regardless of its place of manufacture tends to be acidic due to manufacturing methods used during that time period. This acidity causes the paper fibers to break down resulting in the paper’s embrittlement. Many books in the Yale Library collections printed during this era may have already reached this embrittlement stage. Books in this condition will have to be reformatted; either microfilmed, photocopied or digitized to preserve their information. Today we have an efficient and cost effective technology that will neutralize the acids therebye preventing this embrittlement.

This process is most effective on paper that is acidic but not yet brittle. Determining whether the paper in a book is acidic can be done with a simple test. Using a pH pen that contains chlorophenol red, a small mark is made on the paper. (This is not used on materials of artifactual significance as the mark is permanent. There are other ways to test pH on materials with artifactual value.) This mark will turn a pale purple on alkaline paper and a pale yellow on acidic paper. Most modern papers used today in books produced in the United States, Japan and Western countries are alkaline. However, many other countries are still using paper that is acidic in most, if not all, of their publications. It is this acidic material of more recent production that is the primary focus of Yale's mass deacidification program.

New books printed on acidic paper acquired by Yale Library will eventually become a costly reformatting problem unless they are deacidified. For this reason, the focus of Yale's mass deacidification program is the treatment of recent acquisitions printed on acidic paper. We are currently treating the Burmese Literature Collection and The Near East Collection.