נדה סא, ב
שבעה סמנין מעבירין על הכתם רוק תפל ומי גריסין ומי רגלים ונתר ובורית
There are seven substances that one applies to the stain on a garment to ascertain whether it is a blood stain or a dye, as these seven substances remove the blood. They are: raw saliva…
If you want to know if a stain is caused by blood, rub some saliva on. If the stain disappears, it was indeed blood. That is the claim made in the Mishnah on today’s page of Talmud, and the detergent powers of saliva are discussed in more detail on the next few pages.
נדה סג, א
איזהו רוק תפל תנא כל שלא טעם כלום מבערב…אמר רבה בר בר חנה אמר רבי יוחנן איזהו רוק תפל כל שעבר עליו חצות לילה ובשינה…תנא השכים ושנה פרקו אין זה רוק תפל
What is the definition of raw saliva? Any saliva where the person had not tasted anything since the evening... Rabba bar bar Chana says that Rabbi Yochanan says: What is raw saliva? Any saliva where the person did not eat any food and he passed the middle of the night and he was in a state of sleep…A tanna taught in a baraita: If one rose early in the morning and learned aloud his chapter of the Torah, that saliva in his mouth is not raw saliva, as speech weakens the strength of the saliva…
Saliva as a Detergent
Each of us has used saliva as a detergent countless times. When we lick our lips after a meal, when we lick our finger and rub it onto a stain on our clothes or a smudge of our mascara we are taking advantage of this wondrous substance. Saliva does a number of things: it moistens and lubricate the mouth, clears food particles and bacteria, forms a coating on all the oral surfaces, buffers the acids produced by bacteria, protects the oral tissues and starts the process of digestion. But the Talmud is focused on its properties as a great detergent.
“Dirt doesn’t stand much of a chance against the power of human saliva, apparently.”
Carolyn Sirett is a conservator at the Manitoba Museum in Canada, who used her own saliva to clean a one-hundred and forty year-old painting. Sirett, who is responsible for the long-term preservation of nearly three million specimens in the museum's collection is keen to point out that she was not “actually spitting on or licking mould off the paintings.” Instead, she lightly dampens a cotton swab in her mouth, “preferably before lunch.” She then rolls the saliva swab over the area to be clean, discards it when dirty and repeats the process. Here is what she achieved, cleaning an oil painting from 1869. She must have really good saliva.
“it was noticed that some conservators preferred their own saliva for cleaning fragile painted layers”
the 2018 Ignoble Awards
Every year since 1991 the Annals of Improbable Research sponsors the Ig Nobel awards, given for “research that makes people laugh and then think." There have been some worthy winners, and last year the Ig Nobel Prize in Chemistry was awarded to Paula Romão, Adília Alarcão and the late César Viana, for measuring the degree to which human saliva is a good cleaning agent for dirty surfaces. The trio, from the Instituto Jose de Figueiredo in Lisbon, Portugal, had published a paper back in 1990 titled Human saliva as a cleaning agent for dirty surfaces in which they undertook “qualitative tests and chromatographic techniques on human saliva.” They reported that alpha-amylase was the main constituent responsible for the cleaning power of saliva. Alpha-amylase is the enzyme we use to break down starch, into simple sugars, but it is also used in laundry detergents. Mary Roach, in her laugh-out-loud book Gulp: Adventures on the Alimentary Canal noted that “higher-end detergents contain at least three digestive enzymes: amylase to break down the starchy stains, protease for proteins, and lipase for greasy stains. Laundry detergent is essentially a digestive tract in a box.”
Mary Roach. Gulp: Adventures on the Alimentary Canal. New York, W. W. Norton & Company 2013. p111.
These features of saliva were actually first noted in the Mishnah. And so perhaps that 2018 Ig Nobel award should have been shared between the researchers from Lisbon and the rabbis from Israel.
