I've recently bought a barrel 12" Wollensak Velostigmat Series II from Petzval Paul (many thanks Paul!). I'd like to 'uncork' it and have read the threads on this by Mark Sawyer and Jim Galli.

The front chapter / beauty ring doesn't want to move (I have invested in some decent Heavystar lens spanners), so I've tried access from the rear.

The two sections of the barrel separate, and the back element of the front group has comes out easily. I can see the small screw that limits the 0 to 5 travel but it is under the brass threaded section that joins the two halves of the barrel together. I can't see a way to remove this brass threaded section.

So I'm turning my attention back to the front ring. I've read the interesting thread on 'How to unscrew a stuck retaining ring?' and this has some great advice, although I'm cautious because the glass.

1) Is freezing a bad idea because of the glass? Would differential expansion (by gently heating the outside body metal after freezing) work?

2) I used to restore furniture years ago and I know that a couple of sharp raps with a hammer on the top of a screwdriver will often free up the threads of a rusted-in screw in wood - obviously I wouldn't set about a lens with a hammer and screwdriver but is there a similar shock method to 'break' the stuck threads?

3) Various solvents are discussed in the above mentioned thread. Are these a bad idea where glass is involved? The glass left in the front group is just one element (as far as I can tell) so presuming that the ring comes free the glass could be cleaned but could solvents damage it?

Has anyone done the same with this model of lens? Or had success with freeing front rings?

Any advice gratefully received. There is a wonderful wealth of knowledge and experience on this forum.

Many thanks,
Peter

(ps I'm in the UK so if you're 'over the pond' my replies may seem slow - I'm probably asleep :-)