How much should I dilute hydrogen peroxide to remove lens fungus?

[Kevin Crisp]

That little chip or blemish isn't going to make any difference at all.

Modern lenses are built to really tight tolerances. Many times on reassembly, just the air pressure that builds up as a piece of class is reinserted will stop progress. You need to gently square it up, and use very little pressure when reinserting. Ok to put clean fingers on the outside of the glass to gently push it in; your fingers won't damage the glass and you can clean off the fingerprints on the outside when you are done. Never force anything. If it isn't going in, it probably isn't straight, and I do mean straight.

[Certain Exposures]

That little chip or blemish isn't going to make any difference at all.

Modern lenses are built to really tight tolerances. Many times on reassembly, just the air pressure that builds up as a piece of class is reinserted will stop progress. You need to gently square it up, and use very little pressure when reinserting. Ok to put clean fingers on the outside of the glass to gently push it in; your fingers won't damage the glass and you can clean off the fingerprints on the outside when you are done. Never force anything. If it isn't going in, it probably isn't straight, and I do mean straight.

Okay, thank you.

[Kevin Crisp]

A little late now, but I've never needed something like hydrogen peroxide to clean off fungus. If it is light and feathery even basic lens cleaner will get it off. (I still have a Kodak bottle of it, mostly alcohol, I am sure.) If the fungus has etched the glass, you aren't going to clean the etching off, but it has to be pretty extensive to cause a problem.

If you really want to "kill" off remaining spores before reassembly, an inexpensive UV "C" light will do it with short exposure. Just follow the safety instructions and be completely out of the room when you turn it on. Going forward, control humidity in storage and you should be good. Zeiss officially says relative humidity below 70%, which seems pretty high to me. I keep the darkroom where all my stuff is stored in cabinets in the 40 to 50% range.

[Certain Exposures]

A little late now, but I've never needed something like hydrogen peroxide to clean off fungus. If it is light and feathery even basic lens cleaner will get it off. (I still have a Kodak bottle of it, mostly alcohol, I am sure.) If the fungus has etched the glass, you aren't going to clean the etching off, but it has to be pretty extensive to cause a problem.

If you really want to "kill" off remaining spores before reassembly, an inexpensive UV "C" light will do it with short exposure. Just follow the safety instructions and be completely out of the room when you turn it on. Going forward, control humidity in storage and you should be good. Zeiss officially says relative humidity below 70%, which seems pretty high to me. I keep the darkroom where all my stuff is stored in cabinets in the 40 to 50% range.

Okay, thank you.

[Jim Noel]

Use plain Listerine to kill the fungus.