What are the letters and numbers on Sesame Street made of?

What are the letters and numbers on sesame Street made of?

Looks like Styrofoam.
Or Muppetonium.

I would think Styrofoam would squeak all over the set. Also, what would they use to carve perfect letters and numbers from Styrofoam?

There’s other solid foams that don’t squeak, I was using Styrofoam in a generic sense. (Here comes the letters) Probably should have used polystyrene but I couldn’t remember the term.

Hotwire cutters.

…Knives?

Most foams are moldable (is that a real word?). They blow the foam into a mold, set it with air (at least in the plant where I temped once) and unmold it. Depending upon the type of foam, it is either colored when it goes into the mold or a colored coating is applied.

This isn’t necessarily gospel or technical, but it was my observation when I worked for two miserable weeks at a plant that made novelties like foam balls and bats ~15 years ago.

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