In libraries, archives, and museums around the world, those in charge of protecting cultural heritage struggle with the topic: Gloves or No Gloves? Karin van der Pal’s talk on the contamination of paper surfaces from handling gives measurable data pertaining to the debate.
Van der Pal’s studies in forensic analysis are being conducted at Curtin University in Western Australia. She is currently collaborating with the Indianapolis Museum of Art on the chemistry of latent fingerprints and with Flinders University, in South Australia.
Van der Pal received paper samples from an Australian paper mill to conduct her research. She first solidified her own approach on how to not contaminate the papers she was testing: wearing cotton gloves underneath nitrile gloves she could take off the top layer and replace with a new set of gloves during the process without any of her marks coming through.
Historically, we know that dark fingerprints appear on paper. The edges of leaves in books become discolored as well. But is this a result of dirt, or could it be because of fingerprint oils? Van der Pal explained that the residue left by fingermarks include aqueous deposits, lipids, and dead skin. The proportion varies based on a person’s age, gender, and diet. Another variable on the kind of mark that is left is environmental exposure. If the pages with the contamination are left in the dark, there is little discoloration, but exposure to light causes the marks to darken.
Fingerprint deposits can be a combination of sebaceous oils and sweat from ecrine and apocrine glands. Typically, van der Pal explains that when a finger print is left, the oily sebaceous residue is on top, while amino acids sink into the paper, and the oil residue evaporates. In van der Pal’s experiments, the fingerprints are not visible to the naked eye, so it was necessary to apply an indicator agent that could show the intensity/saturation of the print left on her test papers. Ninhydrin has historically been used, that develops a fingerprint into a pink-purple. 1,2-Indandione/Zn Chloride exhibits color and luminescence and can show marks left up to 150 years old, so van der Pal selected this to use as an indicator.
The goal of the speaker’s most current experiments was to determine how effective hand washing is, if contaminants pass through gloves, and what effect hand gels and sanitizers have on papers. Using the 1,2 Indandione/Zn Chloride, van der Pal was able to determine that no contaminants come through nitrile gloves up to 2 hours. She cautioned that fingerprints and oils can still be picked up onto the outside of the nitrile gloves if one handles doorknobs and keyboards, for example. One also has to be mindful that wearing nitrile gloves for an extended amount of time is very unpleasant, so an option could be to wear cotton gloves underneath.
Van der Pal’s experiments show that 5 minutes after handwashing, the oils in the skin come back, and that 15 minutes after washing, there is more oil than prior to washing because the body is working to redevelop the oil lost.
Hand creams are left on the surface of the paper.
Antibacterial gels also do not prevent oils from being left on paper.
In the future van der Pal expects to study how drying/aging affects a wider range of paper, how long the fingermarks last on the paper, and what effects whether the marks darken.
Questions from the Floor:
Q1: Can you still detect marks on paper that have been washed? A1: Yes, you can still detect marks on paper that has been subsequently washed up to 3 months.
Q2: Regarding gels, how long did you wait until you tried to detect the oils? A2: we tested at different intervals of time.
Q3: Was there a transfer of the materials/paper to the gloves? A1: Reusing gloves can cause a transfer. Some gilding can attach to cotton gloves. Nitrile shouldn’t pick much up.