The Abbey Newsletter

Volume 21, Number 2
Jul 1997

Identification of Spue on Leather Books at Trinity College, Hartford

by Dr. Henry A. DePhillips, Jr. and Michele L. Mader
(Department of Chemistry, Trinity College, Hartford, CT)

Adapted from "Identification of Spue on Leather-Bound Library Books in the Watkinson Library of Trinity College, Hartford, Connecticut," by Henry A. DePhillips, Jr., Leather Conservation News v. 11, # 1-2, Summer and Fall, 1995, p. 8-10. A table giving the titles, call numbers, location and publication date of the 11 volumes analyzed has been omitted due to lack of space.

Abstract: A white creamy material was collected from several volumes of leather bound books in Trinity College's Watkinson Library and analyzed by fourier transform infrared spectroscopy (FTIR), mass spectroscopy (MS), and liquid chromatography (LC). The spue was identified as a mixture of palmitic and stearic acids.


A white, creamy material, termed spue or spew (1) of unknown identity was observed on a number of older leather-bound books in the Watkinson Library. A prior analysis had shown that the spue was not due to fungal or other biological growths (2).

The Leather Conservation Centre in Northampton, England, suggests that spue could be a fatty acid exudate caused by the application of the wrong leather lubricant. For example, a major component of most commercial leather dressings is neatsfoot oil, which has a high free fatty acid content. The spue also could have been formed from naturally occurring animal fats in the skin (3).

Leather dressings are traditionally applied because they are presumed to slow down deterioration, improve appearance, and restore original flexibility and strength. One major problem with applying leather dressings to book bindings is that the process is irreversible and may damage the books more than it aids in preserving them. Oils and fats can actually encourage biological deterioration, form unstable spues, and oxidize, stiffen, discolor and/or stain the books (4). Leather dressings are traditionally used to preserve leather, but their actual effectiveness has not been scientifically examined until just recently. It has been hypothesized that leather dressings are causing more harm to the leather and books than it is helping to preserve them (5).


Sample Collection. Samples from the storage stacks in the Watkinson Library were taken and analyzed within three weeks of collection. The spue was collected from a number of different areas of the archives.

Spue samples for FTIR were scraped from book covers with a microspatula and were deposited in 0.5 dram glass vials with Teflon lined covers.

Samples were also taken from each book for analysis by mass spectrometry (MS). MS solid probe capillary tubes were gently scraped against the edge of the book until an observable amount of spue was collected. The tubes were stored in the 0.5 dram vials.

Once identified as fatty acids, spue samples were methylated using standard protocols and studied by liquid chromatography (LC).

Analysis of the Samples. For FTIR analysis, samples were dissolved in a volatile solvent which was evaporated from drops placed on salt plates. Samples for MS were run "as is." Samples for LC were prepared as described above. Further details of procedures and results will be published in a future communication.

Results and Discussion

Spue from the Watkinson Library was found on leather bound books and resembled white moss. This spue was identified as a major fraction of palmitic acid and a minor fraction of stearic acid, palmitic acid or hexadecanoic acid (CH3(CH2)14CO2H), and stearic acid or octadecanoic acid (CH3(CH2)16CO2H), are carboxylic acids more commonly known as saturated fatty acids.

Most of the spue samples were found on books printed and published from the mid-eighteenth century to the mid-nineteenth century, but one sample was found on a new book printed in 1987. This book was never treated with any leather dressing by the Watkinson Library. The spue on this book was identical to the spue found on all of the other older books.


The curator of the Watkinson Library has suggested that the spue observed on the more recent volume was transported to it through the environmental control system, i.e., through the air. While we cannot eliminate this as a possibility, the suggestion seems unlikely because of the very low vapor pressure of the two fatty acids. On the other hand, it is possible that over time even solids with low vapor pressure could be transported through the air. Even so, we are still left with the question of why spue forms only on some volumes and not others. Indeed, if transmission is through the air, why is spue not found as a condensed residue everywhere?

Several references mention the use of animal fat as a softening agent for leather that has been tanned, particularly during the nineteenth century. The two major fatty acids in animal fat are palmitic and stearic, with palmitic present in the greater amount. Our observation of just this relationship in our spue samples suggests that the spue may arise from animal fat used to soften the leather on the book bindings from which samples were taken. Unfortunately, we are unable to trace the treatment history of the bindings from which spue was used for analysis.

The identification of the white, creamy spue was the major result from this project. However, other questions remain: from where does the spue originate; how can the development of the spue be halted; how can the spue be safely removed from the binding without harming the leather; what, if any, is the effect of the environmental control system; and is the composition of spue the same from every source? Knowing the composition of spue in our library is a first step. Samples from other sources and suggestions for obtaining answers to these questions are welcome.


The authors thank Dr. Jeffrey Kaimowitz, Curator of the Watkinson Library at Trinity College, for suggesting this project and for his help in obtaining sources of information on the problem. We would also like to thank Paul S. Storch, Editor/Publisher of the Leather Conservation News, for sending us informative articles about spue which proved to be excellent background information. We also acknowledge all those responding to the Conservation DistList and the faculty of Trinity College Department of Chemistry who offered assistance and advice.


1. Letter from Walter Henry, Stanford University to Dr. DePhillips, Subject: "Leather Bloom," March 25, 1994.

2. Letter from Frank M. Child, Professor of Biology, to Dr. Jeffrey H. Kaimowitz, Curator of Watkinson Library, Subject: "Nature of the Excrescence on Certain Book Bindings in the Watkinson Library," March 1986.

3. Tuck, D.H., Oils and Lubricants Used on Leather. The Leather Conservation Centre, Northampton, England, 1983, p. 18.

4. Raphael, T., and McCrady, E., "Leather Dressings: To Dress or Not to Dress," Leather Conservation News, v. 1, no. 2, 1983.

5. McCrady, E., "How Leather Dressings May Have Orignated," Abbey Newsletter, v. 14, no. 1, Feb. 1990.

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