If you’re into collecting, chances are that you also enjoy history and historical research. Me too. That’s why I’m placing my 302 restoration on hold for a moment, directing my attention towards what may seem an odd subject… what substance were the cases/bodies of Western Electric telephones made from? The short answer is, “The first 302s were metal, but they switched to plastic at the start of WWII. All phones thereafter were plastic.” That’s about right, but what type of metal? What sort of plastic? As with the 202 before it, the model 302 was introduced with a body made of a zinc alloy. But because metals were sorely needed to wage war, the ’40s saw the alloy replaced by plastic. Some sources would have one believe that the first bomb to hit Pearl Harbor immediately caused phone production to “go plastic”, but a transition period was involved. (Western Electric seems to have been big on transitional periods)
The use of plastics was clearly the future, but what sort of plastic? Plastics such as cellulite, bakelite, rayon and lucite had been around for years, but new formulations were being developed, as well as new uses for the old ones. W/E had been manufacturing handsets from bakelite for some time, and would continue to do so, but opted to go with thermoplastics for the 302 body. Thermoplastic is a tortuously vague term, applied to formulations with wildly varying characteristics. In general, thermoplastics can be distinguished by their response to changes in temperature, melting to liquid with heat and turning hard/brittle with cold. (This contrasts with phenolic materials like Bakelite that burn with the application of heat rather than melt) Western Electric used a proprietary formulation of thermoplastic called Tenite, introduced by the Eastman Chemical Company in 1929. The use of plastic allowed Western Electric to introduce a rainbow of colors, but this was done towards the end of the 302’s tenure with relatively few examples produced. The 500, on the other hand, would carry the colorful-decor torch into the future, making all those black phones look… well, old.
So how about the Model 500? Were they made of Tenite? Only a chemist would know for certain. It appears that they were, the real question being whether all the 302s utilized the material. Was the same plastic used on the black 302s as well as the color ones? Western Electric openly promoted their color 302s as being made of Tenite, but I’ve seen no such declaration regarding the black models. Did the formulation used in model 500s vary? Yes. I’m not an authority on plastics (or telephones, for that matter), but it would appear that they were all thermoplastic, the only question is what type. The earliest 500s were made of what is typically called the “soft” plastic, which was replaced in the early ’60s with yet another thermoplastic, ABS (acrylonitrile butadiene styrene, sometimes called by the proprietary name, Cycolac). The ABS housings proved to be extremely durable, and vastly superior to the previous formulation. Tenite, by the way, is still going strong, and is today marketed as “the natural polymer”, as it is made entirely from trees.