Bakelite and Celluloid — The Differences
by Julie Pelletier Robinson
People interested in plastics often wonder what the differences are between Bakelite and Celluloid. As a plastics historian, I can share those basic differences and the keys to telling them apart without getting overly technical. To begin, let’s take a look at the early history of these two revolutionary materials that had such an immense impact on civilization.
Celluloid came on the scene during the late 1860s when John Hyatt, an ambitious young inventor, was attempting to win a cash prize by creating a substitute for ivory in billiard balls. Hyatt’s experiments began in 1861, and yielded success seven years later when he discovered the action of natural camphor on nitrocellulose (cellulose fiber chemically treated with nitric acid).
The result was an organic and chemical dough-like compound that, once cured until hard, could be molded into shape by the application of heat and pressure. Celluloid was the world’s first successful semi-synthetic thermoplastic, but it had one serious flaw: it was extremely flammable due to the high concentration of nitric acid used in its makeup.
Bakelite, on the other hand, was the world’s first completely synthetic thermoset plastic. It was introduced 40 years after Celluloid in 1909, by Leo Baekeland, a career chemist who was initially trying to develop a durable varnish for bowling alleys. Baekeland combined carbolic acid (also called Phenol) with formaldehyde and ended up with an amber-colored resin that, when heated, turned into a hard opaque mass.
This phenol-formaldehyde solid was ground into powder and then molded by heat and pressure into a material that was practically indestructible. Dubbed Bakelite plastic by the inventor, it was a chemical miracle and the 20th century’s first genuine test tube baby.
Differences in appearance and applications play an important role in deciphering between these two plastics. Celluloid was clear in its original state and could be dyed in a variety of ways to imitate expensive natural materials. Eventually it came to mimic genuine ivory, tortoise shell, mother of pearl, amber, jet, coral and even high grade linen in huge quantities.
Sheets of colorful celluloid were molded into an array of useful and beautiful things, including jewelry, ornamental hair combs, household and vanity items, billiard balls, dentures, fancy boxes, cuffs and collars. Celluloid was an affordable and convincing imitation for costly luxury materials.
Bakelite, on the other hand, was a hard, durable molding material that had excellent insulating properties and thus found its earliest applications in the electrical industry. In its raw state Bakelite was a combination of ground phenol-formaldehyde and dense filler, like asbestos or slate dust. This made the material extremely hard, but also very dark, limiting its color range to black, brown and maroon. Early applications for molded Bakelite included electrical components, knobs, handles and telephones.
It wasn’t until the 1920s that red, green, orange and white (now amber) Bakelite found its way into the home in the form of colorful and novel kitchen accessories. By 1928, Catalin — a purified form of phenolic casting resin in a wide range of opaque and translucent colors — was introduced. It was poured into lead molds and baked slowly to cure. When hardened, the plastic was removed from the molds, machined by hand, then polished by tumbling or buffing.
Cast Catalin, which was more time-consuming to produce and therefore more expensive than molded Bakelite, found uses from the mid-1930s until just after World War II in jewelry, small personal accessories, kitchenware and novel decorative containers. Stylish and colorful cast phenolic radio cases were produced in limited numbers up until the 1950s.
The properties of Celluloid and Bakelite differ greatly. Bakelite is a dense, durable thermoset plastic that resists heat and flame. Once molded, Bakelite and Catalin retain their shape forever. They cannot deteriorate under normal environmental conditions, and they cannot be recycled - they are here to stay.
Celluloid, on the other hand, is a thermoplastic and can easily be manipulated out of shape with the application of heat and pressure. It also burns violently if exposed to flame and will deteriorate under certain conditions due to its semi-organic nature.
So how do you determine if an article is made from Bakelite or Celluloid? The easiest way is to use your newfound knowledge about the appearance and applications of these two materials. If that fails, then there is a simple odor test that can be conducted using hot water.
When both plastics are exposed to temperatures that cause the molecules to move around, they emit telltale odors. Celluloid will give off the distinctive scent of mentholated camphor, while Bakelite smells of carbolic acid (what many refer to as “hot electrical smell”).
In a nut shell, these are the distinctive characteristics of each plastic: Celluloid is semi-organic and subject to decomposition. It is a thermoplastic, rendering it pliable with the application of heat. Celluloid was made primarily to imitate expensive natural materials that were dwindling in supply during the late 1800s. Celluloid was fabricated in a manner that leaves telltale mold lines on many items. Celluloid emits the menthol odor of camphor when subjected to hot water.
Bakelite and Catalin are synthetic plastics made totally from chemicals. Both are thermoset, meaning that their heat-molded shape is set forever. They are flame and heat resistant and will not decompose. Durable molded Bakelite came in a limited range of dark colors. Cast Catalin was carved and polished and exhibits no mold lines. The distinctive odor of carbolic acid can be detected from these plastics by heating the surface either with friction (rubbing a thumb against it) or with hot water.
When I began studying plastics in 1990 as a student at the Institute for the Study of Antiques and Collectibles, very little information was available on early moldable materials. A research paper assignment led me to explore the subject of Celluloid. My paper was published in article form “John Wesley Hyatt and the Invention of Celluloid,” in the June 19,1995, edition of AntiqueWeek.
This led to the writing of the book “Celluloid Collector’s Reference and Value Guide,” by Julie Robinson and Keith Lauer (curator of the National Plastics Museum) published in 1999 by Collector Books. A new title “Celluloid Dolls, Toys and Playthings” by Julie P. Robinson, 2005 Collector Books, has just been released and is available from the publisher. Autographed copies may also be secured from the author, who may be reached at email: JulieRobinson@celluloidforever.co
I frequently am
lecture on the subject and also have built up a following of collectors
send me celluloid toys and other items for repair.
Julie P. Robinson, author of Celluloid Collector’s
Reference and Value Guide and
Celluloid Dolls, Toys and Playthings.