That ad should be photoshopped to say:
"Tenite; Cheese it's good!"
I don't think that is fair. The Tenite used for these housings did not smell. It was cellulose acetate, Kodak called it Tenite Acetate in trade. This is a different material than the Tenite used in the 500 sets of the 1950s.
The Tenite of the 500-series, that after 50+ years smells so badly, was Tenite Butyrate, or cellulose butyrate, a different derivative of the cellulose material, which contains a little larger monomer molecule. The reason it smells is because the butyrate breaks apart and forms butyric acid, which cases the smell. It is the same substance that accumulates in rancid butter causing a similar odor. Butter <---> butyric acid <---> butanone <---> butane, that is the historical naming connection. Butane is a chain of four carbon atoms, the basic backbone building block for all of these.
Tenite Butyrate appears to have one advantage over Tenite Acetate, it does not decompose as much as the acetate. Products from cellulose acetate have always had this problem shrinkage.... the celluloid dial card windows, the cellulose acetate dial number plates, etc... Acetate has a carbon backbone of only two molecules and disassociate from cellulose apparently much more readily than the longer chains. This is the reason for the shrinkage of the Tenite 302 telephone housings. The acetate simply decomposes into water vapor and carbon dioxide which just diffuse out of the plastic. Ergo, the plastic shrinks over time.
The butyrate does not break down to water and CO2, and therefore does not escape the bulk of the material by diffusion, it is too big a molecule for that. Therefore the material does not shrink, but does become more brittle after decades.
Eastman Kodak also made a Tenite version with the intermediate alkane chain, Tenite Propionate, which has three carbon atoms in the chain, and should probably have properties somewhere in the middle between the others. I don't think it is known whether this was ever used for the manufacture of telephones. It certainly seems like that Bell Labs, or somebody, would have run tests.
