Ebonite/Bakelite?

[ms660]

I have a front control panel on a mid 1920's receiver, it's black, about 6mm thick, I need to determine if it's ebonite or bakelite or whatever.

A piece had already broken off one corner, it looks like a clean very sharp fracture, I'm thinking of a hot needle or nail on the fracture surface for a test.

Any good? Anyone with practical experience?

I don't want to damage the front, rear or edges of the panel for any kind of test.

Lawrence.

[David G4EBT]

I think it’s more likely to be Ebonite than Bakelite. To test, a hot needle won’t have any effect on Bakelite, but it would on Ebonite, which is basically vulcanised hard rubber with a high proprtion of sulper and linseed oil added. It was (is) the brand name used by the inventor Charles Goodyear back in the mid 1840s. It’s still used extensively for such things as smoking pipe mouthpieces, fountain pen bodies and nib feeds, (eg, Mont Blanc pens!), and saxophone and clarinet mouthpieces.

https://en.wikipedia.org/wiki/Ebonite

Hope that helps a bit Lawrence.

[ms660]

The band change switch rotors in the receiver appear to be made of the same type of stuff though not polished, they are about 25mm in diameter.

The hot needle test is the way I'll probably go, this early radio stuff is new to me as far as materials go.

I shall report at some time.

Cheers.

Lawrence.

[greenstar]

If it's a sharp glassy edge, possibly formica? This was around since the 'teens, I think. It appears in the early magazines.
Tony

[ms660]

Test result using a panel pin heated to cherry red:

It's ebonite, at least that's the indication I'm getting, panel pin made a sizzling noise on contact and made a hole, smoke and the smell of old rubber.

Lawrence.