Brass Lens Corrosion

[illumiquest]

I found a Darlot Paris Petzval at my local antique shop (score!) but the thing is in pretty poor condition. The glass actually looks very good except for separation on the front element which is an easy fix if I could get the thing out. It looks like the lens was either damp or in water for some time and there's white crusty stuff inside the barrel and I'd imagine it's on the threads too. The rear element threaded out fine but the front is still stuck.

I've tried using PB blaster, a penetrating oil for several hours and that's not getting me anywhere. Any suggestions on what would break these things apart would be greatly appreciated.

Thanks!

[paul ron]

Try some heat (put in the sun for a few hours) and if that doesn't work freeze it to shrink the metal, that may free it.

Be sure to use a strap wrench so it applies even preasure so the soft brass doesn't deform.

[c.d.ewen]

Be sure to use a strap wrench so it applies even preasure so the soft brass doesn't deform.

Careful! A strapwrench used gently is good, but it doesn't apply even pressure. I learned the hard way years ago. You're putting a lot of downward pressure under the handle.

Charley

[Rick A]

Some carefully applied heat to the threaded area, then the addition of penetrating oil while hot, should help break the corrosion free and allow the lens to be taken apart.

[illumiquest]

I ended up cutting two slots in the retaining rings to get a spanner in but that still wouldn't do it even with heat so I ended up denting the retaining rings in with a pair of pliers and pulling them that way. There was about 1inch of threads, the penetrating oil had saturated all the way through but the brass is so soft that it was just flexing and jamming when I tried to unscrew it. Got the elements out, and working on recementing the front one. Should have a working lens by tonight.

[illumiquest]

Well, it works!

[zsas]

Wooooooo hooooooo!!! Congrats!