Canada balsam separation repair??

[John Cahill]

I have an enlarging anastigmat which I am told has some separation of two elements. It looks like a partial halo around the center of the lens. I was advised to place the cell in a cold oven, very, very slowly (over several hours) raise the temp to ca 175 deg F., for a couple of hours, then, equally slowly, lower the temp and that PERHAPS the problem might resolve. As it is now, I have a decent paper weight. Any comments or suggestions are welcome.

[Kevin Crisp]

I am perhaps overly conservative in how I do this, but I haven't broken one yet. With the partially separated cell out of its housing, put it on crumpled aluminum foil in a cold oven. Have the lens tilted at about 45 degrees or so. Turn the oven up to 100-125. Every half an hour bump it up 25 degrees. When it gets close to coming apart the aroma will fill the kitchen. They will slide apart when it gets up to 300-325 F. The upper should slide off the lower if the lens is an at angle on the foil.. Otherwise, take the foil out and push the lenses apart with a tooth pick. Put the foil with the lenses on top back in the over. Turn the oven off and leave the door closed. It will slowly cool off. Soak them in Acetone to get the residue off.

In another thread it is suggested that merely a long soak in solvent may do this, you might want to try that first.

At least when I have done this, nothing happens at 175 degrees, but I didn't maintain that temperature for a long time. Good luck.

[John Cahill]

[At least when I have done this, nothing happens at 175 degrees, but I didn't maintain that temperature for a long time. Good luck.[/QUOTE]

*****
Hi Kevin,
Thanks for the specifics. I will give it a try. The lenses are encased in metal, as far as I can see and I do not see how they can be separated. Do you think that if I tried your approach, the balsam would just kind of ooze back to where it should be?

John

[Glenn Thoreson]

I soak them in acetone or cheap laquer thinner for a couple of days. When it's ready, it will slide right apart when you agitate it. Then after a good cleaning, a drop of UV cure optical cement will have it back like new. If you take it apart, be sure to scribe a reference mark on the edge, so you get it back together the same way. I use a Dremmel tool and a diamond bit for that.

[Kevin Crisp]

You can't separate the lenses in the mount, big mistake. (You can't reglue them in the mount either, so even if you could separate them in the mount, why bother?) You have to get them out of the mount. Usually, there is an inner ring that unscrews and you take the elements out from the back. Sometimes there is a retaining ring in the front with slots and you unscrew that and take the elements out of the front. Sometimes the ring has no slots and you have to drill small holes in it to get something for a wrench to work on, or use one of the rubber round things sold by Microtech for this purpose.

Sometimes the lens is burnished into the mount, meaning the metal is rolled over or formed to hold it in. (This is covered on the Grimes web site.) Those are a real pain.

[Glenn Thoreson]

Kevin's right. I must be removed from the mount. I should have made that clear in my post.

[John Cahill]

Kevin's right. I must be removed from the mount. I should have made that clear in my post.

Thanks, guys. I see no way whatsoever to get the lenses out of the mount. I guess I'll just shut the oven off right now, let it cool, and tomorrow begin to use the ek annie as a paperweight.

[Glenn Thoreson]

Have you used it as is to see what the effect on performance is? It doesn't always have any effect at all.

[John Cahill]

Thanks, again, Kevin and Glenn. No way I could separate the cell. At any rate, I gave the cell a "full treatment" and then some. I upped it as recommended and let it go over night at 200 degrees, then upped to 300 for another two hours, letting it cool in a closed oven all day. It may be wishful thinking, but the lens appears to be clearer than when I began. At any rate, I shall give it a try. It may be more than a paper weight after all.