A Benign Spit-Shine

Laura Webb, Program Specialist

Hello again, folks! We’re now halfway through our NEH grant timeline. I’m approaching the home stretch of object editing, and will soon begin photographing select items. In the meantime, let’s chat about artifact conservation!

In going through object entries in PastPerfect, I have also been checking our maintenance and conservation notes entered into the system from past conservator reports. Early on in this project, one word in these notes caught my eye: “saliva.” At first, I thought this must be some sort of typo. Then, after finding several more examples, I wondered if it was a faithful documentation of a (surely!) outdated practice. After all, artifact conservation techniques have certainly changed a lot over history. Out of insatiable curiosity, I dug a little deeper.

Object SP82.3.3; Past Perfect records: wooden colander of basswood, made at Hancock Village, MA; museum purchase, 1982. Mechanically cleaned, cleaned with saliva, treated with wax (1996).

I found out that cleaning artifacts with human saliva—known colloquially as a “spit shine,” and scientifically (albeit euphemistically) as “enzymatic cleaning[1]—is a conservation technique that has been used for centuries.[2] However, it also (surprisingly enough) has scientific backing! A 1990 Portuguese study confirmed that the amylase enzyme contained in human saliva makes it, for many delicate surfaces, a more effective cleaning agent than water, while still being gentle enough to use on sensitive materials.[3] The authors won the 2018 chemistry “Ig Nobel” prize for unusual achievements in scientific research for their study.[4] It has also been investigated for use on silver gelatin photographic prints—although with mixed results, and further study needed.[5]

Object 74.6.1; Past Perfect records: split wood basket with a fine weave, made at Sabbathday Lake, ME; donation from 1974. Cleaned with saliva, old PVA glue removed from a previous repair, re-glued with hot hide glue (mid-1990s).
Object 62.4.6; Past Perfect records: hand-carved ash dough trough; on long-term loan since 1962. Cleaned with saliva, waxed with Behlen’s Wax (1996).

As y’all might imagine, the Covid-19 pandemic has caused this practice to be put on hold in some institutions, while others are putting it under closer scrutiny and modifying their procedures to increase sanitation.[6] Synthetic solutions that imitate saliva have also been tested, and appear to be just as effective, but of course are more expensive than…well, than fluids humans naturally produce anyway.

Regardless of what future studies determine, we can understand how important it is to document all past conservation treatments on an artifact! Have you ever seen old glue turn yellow on something? Yep, that’s not what we want. Our standards, knowledge, and available materials change over time, and sometimes it is necessary to undo past work for the longevity of an object.

Object 61.3.327; Past Perfect records: cherry pitter with an oak handle; donation from 1961. Mechanically removed corrosion, cleaned with mineral spirits, wooden handle cleaned with saliva, waxed all surfaces (mid-1990s).

While past conservators at Pleasant Hill have used this technique, I could not find a record of it being used since the mid-1990s, and none of these items are currently on display—so you don’t need to worry about our current exhibits! In general, though, perhaps…don’t lick the artifacts.

[1] Allison Rosenthal, “Spit Cleaning: Conservation’s Dirty Little Secret” (Buffalo Bill Center of the West, July 9, 2015), accessed September 18, 2020, https://centerofthewest.org/2015/07/06/spit-cleaning-conservations-dirty-little-secret/.

[2] Steven Litt, “Little-Known Art-Cleaning Technique Nothing to Spit At,” The Seattle Times (The Seattle Times Company, April 7, 2002), accessed September 18, 2020, https://archive.seattletimes.com/archive/?date=20020407.

[3] Paula M. S. Romão, Adília M. Alarcão, and César A. N. Viana, “Human Saliva as a Cleaning Agent for Dirty Surfaces,” Studies in Conservation 35, no. 3 (August 1990): pp. 153-155, accessed September 18, 2020, https://doi.org/10.2307/1506167.

[4] Emma Stoye, “Art Conservation Using Saliva Wins Chemistry Ig Nobel,” Chemistry World, September 14, 2018, accessed September 18, 2020, https://www.chemistryworld.com/news/art-conservation-using-saliva-wins-chemistry-ig-nobel/3009504.article.

[5] Ruth Oliver, “May I Spit on Your Photograph? A Preliminary Investigation into the Effectiveness of Saliva and a Synthetic Alternative for Surface Cleaning Silver Gelatin Photographs,” in 4th Book, Paper & Photographs Symposium, 2006, pp. 174-193.

[6] Luke Wong, “Coronavirus Puts Damper on Saliva Cleaning Method in Art Galleries and Museums,” ABC News (ABC Central West, June 27, 2020), accessed September 18, 2020, https://www.abc.net.au/news/2020-06-28/saliva-spit-cleaning-art-gallery-museum-conservator-pandemic/12398824.

Shaker Village