I can't say I've seen anything like that on hundreds of typewriters I've handled and thousands I've seen pictures of. Can you show some pics? It certainly was not a practice to treat platens with a powder at any period. I have often seen what looks like a powder on certain plastic keytops, notably Royals, but that isn't really a powder but a chemical consequence of aging, but platens are a completely different material. I suppose a very dense sprinkling of Wite-Out or correction flakes could look like powder.... Puzzled.

I've seen this in very old rubber products. I think it is from some type of degradation. I used to work in a bicycle shop that catered to owners of vintage bicycles. I mean VINTAGE. We had lots of stuff from back when the bicycle was called the "safety bicycle" after the decline in popularity of the high wheeler. Some very old tires (or tyres) often have a white powdery or even flaky stuff on them. It's not talcum powder, which is used inside tires to help keep the tubes from sticking and tearing the stems off. It's something else that I've only seen on vulcanized rubber. I've also seen a similar degradation on latex bike stuff, like tubes but that type of rubber usually dries and cracks long before it turns to powder.

Phil Forrest

AndrewP wrote:

Every now and then I see typewriters where it looks if there is a white powder (like talcum powder) on the platen. Now I wonder how does the powder get there?

Was it common in the 60s and 70s to treat the platen with some powder? Or is it some kind of ageing of certain types of rubber?


 

It could be the owner of said typewriter was using excessive amounts of Columbian marching powder whilst on marathon typing sessions and some of it spilled on the platen .

Seriously though, it is more likely to be the 'bloom' of oxidation, of the rubber, which occurs with the prolonged exposure, over time, to the UV light component of sunlight and the atmosphere in general. 
 

I was wondering too what it was. Most of my Triumph/Adlers build after 1963 have it, although very little.