removing white chalk/smeg from nos comp 3's

[kowalski]

as above just received a pair of nos comp3 tyres and have unwrapped them and tried scrubbing this horrible white stuff off with warm water and soap but its not shifting, any advice peoples please i assume this white chalky like film is quite usual on old tyres?

[MartyC]

The white powder is usually the powder to stop the tyre sticking to the mould when they are made, I've never tried to remove it any other way than by riding them.  You could try one of those car tyre cleaners like the Wynns Tire Restorer or maybe the tyre black sprays.  How bad are they?

[snav69]

I use my jet wash on them and it gets rid of it just fine 
Mount them to an old wheel and lay it on a bucket then you just blast it off , never damaged a tyre yet 

 

[kowalski]

cheers for the advice boys they are quite bad!
i don'thave a jet wash unfortunately but this morning now they have dried out it seems to be coming off with a good hard scrub with a stiff nail brush
god this bmx resto lark is hard on the arms and the wallet