How much wattage is needed w/ a Germicidal UVC bulb in order to stop lens fungus?

gone · Dec 7, 2022

We're socked in w/ rain for a while, but I'd like to stop the fungus from spreading on the rear element of a lens. These bulbs come in all manner of prices and varying amounts of wattage. I like the bulbs that have screw on threads (like a conventional bulb) because you don't have to buy a fixture for them.

Am I right in assuming that even a low wattage bulb would work if left on long enough? Or would I need a bulb with higher wattage to do the job?

DREW WILEY · Dec 7, 2022

After putting a lens in a sealed silica-gel desiccation chamber for a few weeks, I just use strong window light. But if you find a traditional UV sunlamp, just be personally careful with it in terms of eye protection as well as fire risk. Halogen style ones can be especially risky.

psmithp · Dec 7, 2022

momus said:
We're socked in w/ rain for a while, but I'd like to stop the fungus from spreading on the rear element of a lens. These bulbs come in all manner of prices and varying amounts of wattage. I like the bulbs that have screw on threads (like a conventional bulb) because you don't have to buy a fixture for them.

Am I right in assuming that even a low wattage bulb would work if left on long enough? Or would I need a bulb with higher wattage to do the job?

I suggest you by a hygrometer, calibrated to show the relative humidity in pct. I believe you should heat so much that the RH is 60 or lower (wiser minds please correct me if am wrong). 25 watt in a small cupboard worked fine for me in Equatorial Africa.

DREW WILEY · Dec 7, 2022

Another risk with high wattage is that it might damage the lens sealant.

gone · Dec 7, 2022

Thanks very much. I'll use a low watt bulb, and just put it and the lens in a partially opened drawer w/ the opening toward the wall for maybe 4 hours a day, for several days. Normally I would just set it in the sun, but we're not going to have much of that here for a spell. At some point the lens will have to come apart to clean it, but this will at least halt the spread of the fungus

koraks · Dec 8, 2022

I'd be wary of leaving a bulb on within a partially closed drawer because of the fire risk. Any UV-C lamp will have power supply electronics that feed the fluorescent or (these days, more likely) LED element and those electronics get hot and moreover can fail (sometimes catastrophically). Keeping the bulb surrounded by combustible material sounds like a bad idea, especially if you run it for an extended period of time in a confined space. Why not just put it in the windowsill and have a bit more patience?

maltfalc · Dec 22, 2022

ZERO. NONE. NADA. there is absolutely no need to ever use uv-c on a lens. uv-c degrades paints, plastics, adhesives, rubber, leather, etc., and won't penetrate the interior of a lens, so it won't kill any fungus that isn't on the outer surface of the lens. it will however do severe damage to your skin and eyes in a matter of minutes if you're in the room when it's on. we're talking severe sunburn, blindness and in the long term, cancer. even with low wattage bulbs. just don't do it. the ONLY thing you EVER need to do to kill fungus is avoid high humidity. that's it.

How much wattage is needed w/ a Germicidal UVC bulb in order to stop lens fungus?

gone

DREW WILEY

psmithp

DREW WILEY

gone

koraks

Moderator

maltfalc

Privacy & Transparency

Privacy & Transparency