A Brief History of Parafilm
Answers to “Is it edible?” and other burning questions.
Welcome to Codon, a newsletter about the intersection of biology and technology. This essay was co-authored with Metacelsus, who writes the always excellent De Novo newsletter.
Cling wrap on steroids. The duct tape of science. The Forbidden Cheese.
Parafilm is a laboratory mainstay. It is a bit like plastic wrap, but also way better. It is translucent, odorless, and tasteless. It’s incredibly stretchy — Sigma-Aldrich says parafilm can stretch up to 200% in length, but we’ve heard tales of graduate students who achieved feats far greater than that. Parafilm sticks to itself. It’s waterproof. It dissolves in hexane. It’s slightly thicker than a sheet of paper. Biologists and chemists use it to seal petri dishes and bottles, because it keeps in liquids but is permeable to most gasses.
If you take a two-meter square sheet of parafilm, at room temperature, and wait for twenty-four hours, about 0.46 grams of oxygen, 0.12 grams of nitrogen, and 2.0 grams of carbon dioxide will pass through its pores.
The question of whether parafilm is also permeable to water, though, has been the source of many heated debates.
The product information documents from Sigma-Aldrich say that parafilm is “permeable to gases, but highly insensitive to moisture loss and moisture absorption.”
But that’s (sort of) a lie. Parafilm is permeable to about 0.88 grams of water vapor per square meter of material per day, which is actually quite a lot. The permeability of parafilm was also studied, against a battery of chemicals, way back in the 1960s. Those data confirmed our suspicions.
Properties aside, where did parafilm come from? Despite the internet’s deep affection for the material, and countless memes revering its utility, parafilm’s history is shrouded in mystery. There is a chasm that separates its internet devotees, on the one hand, and our actual understanding of where it came from, and how it works, on the other. So we went out and answered your burning questions:
What is this stuff? Where did it come from? Can you eat it?
The history of parafilm is indelibly tied to the history of paraffin, which was first discovered nearly two hundred years ago. In 1830, a German jack-of-all-trades named Carl Reichenbach (who had a strange obsession with extracting stuff from tar) cooled petroleum and noticed that a thick layer of wax formed on top. He dubbed this wax paraffin, from the Latin for parum and affinis, meaning “very little” and “lacking affinity.” People used the oil wax to make candles. Its name was reminiscent of its cheap, inert qualities.
For decades, paraffin remained a niche obscurity. Petroleum was still, at the time of Reichenbach’s discovery, quite scarce. But everything changed in 1859, when Edwin L. Drake drilled the first-ever oil well in the small town of Titusville, Pennsylvania. In the years that followed, hundreds of wells were drilled across America and paraffin wax quickly became commercialized. Most American homes used it to make candles by the 1870s.
Paraffin, in the following decades, also found a fair number of uses in high-profile physics experiments.
In 1932, James Chadwick, the Nobel Prize-winning physicist, used paraffin to discover the neutron. He stuffed chunks of wax inside his neutron detector, and then blasted a beryllium target with radioactive particles. Neutrons were detected when the high-speed particles “dislodged protons from a piece of the wax.” A replica of Chadwick’s neutron detector is on display at the Science Museum in London. A photo of the original wax — which has, for some reason, turned a deep blue — can be viewed online.
Enrico Fermi extended Chadwick’s experiments two years later, using paraffin wax to make groundbreaking discoveries in radioactivity. For months, Fermi had been attempting to produce “artificial radioactivity” by placing a bar of silver inside a lead container and then blasting it with a stream of radon. He placed various metals and heavy leads between the radon source and the silver bar, but was unable to get results; his Geiger counter emitted only feeble beeps.
And then, on the 22nd of October in 1934, eureka! Fermi replaced the ‘various metals’ with paraffin wax. And then, “the Geiger counter showed the artificial radioactivity of this silver sample to increase by up to a hundred times,” according to an article from The Franklin Institute. “Fermi's explanation was that the multiple hydrogen atoms in the paraffin effectively ‘slowed’ the neutrons to a state that permitted many more collisions with the atoms of silver. The next amazing possibility of controlled or ‘harnessed’ radiation exposure by neutron bombardment was near.”
Around that same time, paraffin was also being used in medicine. In the spring of 1922, an 8-year-old girl — known only by the initials V.R. — “was scalded by boiling water.” The healed wound and scars were so thick that she had difficulty moving her elbow.
The following year, in May, a physician in Onaway, Michigan (population in 2021: 899) named L.D. McMillan “removed about a square inch of scar tissue contiguous to the healthy skin, and dressed the wound daily with surgical paraffin (parresine—Abbott), after the usual method used for burns,” according to a 1923 paper in the Journal of the American Medical Association.
V.R. was then put under anesthesia. McMillan “removed the main portion of the scar over an area of 20 square inches, including the anterior surface of the elbow, thus severing the tissue fixing the elbow and allowing the arm to be straightened and splinted in full extension. In two weeks, most of the defect was filled in and epithelialized.”
Paraffin, it seemed, had healing powers.
By 1939, a busy cadre of German chemists had devised clever methods to make highly pure paraffin wax. The German gas company, DEA Deutsche Erdoel AG, obtained a patent for the technique, which involved treating crude wax with ‘bituminous tar,’ phenols, and then an adsorbent carbon.
But this essay is about para-film; not paraffin. The word “parafilm” was first trademarked by the Marathon Paper Mills company in 1934. The company called it a moisture-proof, self-sealing flat wrapper. Today, the product is classified as “paper, cardboard and goods made from these materials,” and so it was effectively lumped, by the U.S. Trademark Office, in the same category as paint brushes and stationery.
To this day, few people know the secret recipe to make parafilm, even though its formulation has remained basically the same since its commercialization in the 1930s. We know it is made from 56 percent wax and 44 percent polyolefins, and that it has a boiling point “above 550 degrees Fahrenheit,” because a 1998 datasheet from the University of Wisconsin - Whitewater says so. But if you ask Elicit — the AI-powered science paper search tool — “What is the chemical composition of parafilm?” you’ll get an error. (It’s almost like the parafilm powers-that-be are holding their recipe away from prying eyes. Or maybe it’s just my internet connection.)
Parafilm wasn’t initially marketed to research scientists. Its intended use, in the 1930s, was for map mounting, in which a flat layer of parafilm is placed between a map and fabric, and then a hot iron is applied for about ten seconds. The parafilm wax partially melts and joins the map to the fabric. This technique — which also works for Boy Scout patches — made maps more resilient for sailors exposed to saltwater and harsh ocean winds.
By the 1950s, though, parafilm was explicitly being touted as a ‘wonder material’ to scientists across the U.S. A 1952 ad in Scientific American priced a roll of the material, 18 inches wide and 25 feet long (about 3.5 square meters in total) at just $3. A similar amount, today, costs about $40 on Amazon. The ad was deceptive, however — it described parafilm as “airtight,” which simply isn’t true.
A few years after Marathon Paper Mills trademarked and manufactured parafilm, World War II broke out in Europe. By 1943, gasoline, sugar, coffee, canned foods, meats, and butter had all been rationed in the U.S. If you wanted to buy oils or fats, you had to spend points at the local grocery store. “Each person received 64 red stamps each month,” according to blogger Sarah Sundin, and butter cost more points than either margarine or lard.
Scarcity accelerates creativity. “Paraffin was used in baking during World War II when rationing and scarcity made butter and shortening hard to come by,” according to a blog by Templa Melnick. A sponge cake recipe from the era calls for 5 tablespoons of self-raising flour, 3 tablespoons of sugar, and 2 tablespoons of liquid paraffin. Even today, paraffin wax is used in some chocolates because it blocks bacterial growth.
So, to answer your question….yes. But we don’t recommend it.
Even though “paraffin is usually nontoxic [...] if swallowed in small amounts,” according to a Mount Sinai medical page, “the person will likely be asked to drink large amounts of fluids to help move the paraffin through the bowel,” where the waxy substance accumulates and can cause blockages.
A decade after the war’s final echoes rang through Europe, the Marathon Paper Mills Company sold its Wisconsin plant to the American Can Company, one of the largest military contractors during World War II. The American Can Company manufactured tin cans and parafilm for decades, well into the 1990s. In 1957, they also acquired the rights to Dixie cups, those little paper cups next to water coolers at dental offices.
But then, in the mid-1990s, parafilm was acquired by Pechiney Plastic Packaging, Inc., a company with a very boring name. (There seems to be a negative linear relationship between the ‘coolness’ of a name and the year it was founded.) In 2010, Pechiney was purchased by Curwood, part of the Bemis Company, which is headquartered about 40 miles southwest of Green Bay.
The Bemis company has an inordinately rich history. Founded in 1858 in St. Louis, Missouri by Judson Moss Bemis (that’s one helluva name), they were one of the country’s largest makers of cotton bags. Mr. Bemis opened a second plant in 1880 in Minneapolis, and then ten others in counties across the U.S. Their logo, until 1962, was a little cat named Biddy.
In 2019, one of the world’s largest packaging companies, Amcor, bought out Bemis for $5.25 billion. Parafilm, though, is still manufactured in Bemis’ Wisconsin plant.
Alas, this is where we must pause and make a confession. Throughout this essay, we have been lying to you. Pechiney, Bemis, and the other companies did not sell ‘parafilm;’ they made Parafilm-‘M’. Unfortunately, nobody actually knows what the ‘M’ stands for and, when we emailed their corporate address and asked (in a very sweet tone), the company didn’t reply. Yet another mystery, it seems, destined to go unanswered.
Today, parafilm is used across a startling array of scientific experiments. Some biologists use parafilm to form ‘cell spheroids’ — three-dimension balls of cells that mimic tissues — or to keep plant stems fresh during grafting. Others use it to feed bed bugs. Parafilm can be stored for years — maybe decades? — and nothing will happen to it. Dentists use parafilm to stimulate saliva production.
In one study, patients were asked to chew either a bit of parafilm or cheese. Parafilm caused “immediate increases in plaque pH [...] with concomitant decreases in lactate and acetate concentrations and increases in the concentration of formate and many amino acids,” according to the study. Cheese, incidentally, caused the mouth to produce similar levels of “formate, lactate, and propionate.” (Maybe parafilm really is the forbidden lab cheese.)
Despite its inert nature, it’s not always good to use parafilm to seal plates or bottles. In one study, agar petri dishes wrapped with parafilm affected the larval development of C. elegans worms. After 48 hours of growth, worms on plates sealed with parafilm grew about 6 percent faster than the control plates (but the data, even if you squint a little, are close.)
More recently, parafilm has been used to make simple, paper-based analytical devices to study human cells, or to craft microfluidic devices that move tiny volumes of liquid through little, wax-coated channels. Outside the laboratory, parafilm has even been used to patch holes in a tire or seal drafty windows.
Is there anything parafilm can’t do?
Thank you for reading.
Metacelsus writes De Novo.
 | A guest post by
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The ‘M’ in parafilm is indeed a mistery.
Could it be the’M’ from Marathon Paper mills or the Map Mounting application?