Fungus killers

Following-on from the "camera bag" thread where silica gel and desiccants are mentioned, what other fungus killers do you use?

 

I suspect one of the best is sunlight. Direct sunlight contains deadly shortwave UV rays, and the inside of a lens in sunlight would be a very hot greenhouse - I doubt many funguses could survive that kind of treatment.

 

Would UV lights work when sun is unavailable? Longwave UV is used in "detection" and bounces off does without penetrating surfaces, making it a less effective killer. Shortwave is deadly but its expensive - the cheapest source might be pond filter equipment.

 

I am tempted to give my lenses an annual bathing in shortwave UV. What are your views?

Edited February 7, 2021 by G&R

(Short) UV works very well. It is used in microbiological and pathological labs. But after everybody has left. Not very healthy.

 

You could give it a try. Sunlight will do as a good substitute. And if you do give UV a try, once per annum is not often enough.

There are a myriad of threads on this topic on the web. Preventive maintenance is the best policy...low humidity and circulating fresh air, light, no leather or closed lens cases other than for transporting lenses. As far as killing fungus, some are killed by sunlight, some by hydrogen peroxide, Some fungi can etch the glass permanently. I wouldn't unnecessarily clean a lens. Leaving some lenses in sunlight long enough to kill fungi could heat the lens and vaporize some of the lubricants, which could then redeposit on the lens elements creating haze or diaphragm blades making them sticky and less responsive.

According to Zeiss, "Reduce the relative humidity to less than 60% (never under 30% as it is dangerous for the instrument) by storing ... in a special cabinet whose interior is heated to 40°C (max. 50°C) using a fan heater/ incandescent lamps, thereby reducing the relative humidity"

 

Helpfully, according to FineDiningLovers, "At this point, there are two choices: if you have an oven that can maintain a low temperature, set it to 45 °C. If not, bring the oven to the minimum temperature it can handle, then turn off the heat and wait until it goes down to 60 °C. That way, when we open the door of the oven, the temperature will descend to 45 or 50 °C."

 

;)

According to Zeiss, "Reduce the relative humidity to less than 60% (never under 30% as it is dangerous for the instrument) by storing ... in a special cabinet whose interior is heated to 40°C (max. 50°C) using a fan heater/ incandescent lamps, thereby reducing the relative humidity"

 

Helpfully, according to FineDiningLovers, "At this point, there are two choices: if you have an oven that can maintain a low temperature, set it to 45 °C. If not, bring the oven to the minimum temperature it can handle, then turn off the heat and wait until it goes down to 60 °C. That way, when we open the door of the oven, the temperature will descend to 45 or 50 °C."

 

;)

Yeah... for storage...

Yeah... for storage...

If you have a glass front on the oven it could be for display... :eek:

 

... or vivarium display cabinets (thermostat with ceramic heater or heat map) are already tuned to maintain a permanently dry 45°C. They even have a little UV. What could be better?

The thing with the Zeiss advice is the assumption that air at 40 degrees contains relatively low amounts of moisture (lower than 60%).

But it could also be steaming wet, dripping even, at 40 degrees Celcius. That fan could just be blowing in more moisture.

Fungus incubators, those cabinets. Temperature is not the main thing. Relative humidity is.

The thing with the Zeiss advice is the assumption that air at 40 degrees contains relatively low amounts of moisture (lower than 60%).

But it could also be steaming wet, dripping even, at 40 degrees Celcius. That fan could just be blowing in more moisture.

Fungus incubators, those cabinets. Temperature is not the main thing. Relative humidity is.

Floor of desiccant in the vivarium? :)

 

Perhaps the worst accessory one can add to their camera is a UV filter because any UV filter will protect fungus spores from deadly rays.

Edited February 10, 2021 by G&R

 

Perhaps the worst accessory one can add to their camera is a UV filter because any UV filter will protect fungus spores from deadly rays.

 

Hmm... now you tell me...

http://bayouline.com/o2.gif

I'm from Missouri on that one!

I'm from Missouri on that one!

According to research published a NCBI, a 254nm UVC light source was shown to cause fungal deactivation.

Light based anti-infectives: ultraviolet C irradiation, photodynamic therapy, blue light, and beyond

 

The following UV filter test results claim that 254nm is blocked by the most effective and least effective UV filters. Hoya scored highest for blocked UVC penetration from 200nm to 380nm. The least effective in the test also blocked the 254nm UVC. In other words the frequency that has been shown to deactivate fungus is blocked by UV filters.

UV filters test - Hoya 72 mm HMC UV-0 - LensTip.com

UV filters test - Tiffen 72mm UV - LensTip.com

 

With respect to vintage lenses, have I missed something?

Edited February 11, 2021 by G&R

...In other words the frequency that has been shown to deactivate fungus is blocked by UV filters.

 

Hmm... just had to buy 11

L1Bc Nikon skylight filters...

http://bayouline.com/o2.gif

Hmm... just had to buy 11

L1Bc Nikon skylight filters...

I think skylight filters are UV filters with an orange/magenta tint, but in either case, I don't think anyone should base buying decisions on anything I post :oops:

I think skylight filters are UV filters with an orange/magenta tint...

 

Hmm... today ain't my day...

http://bayouline.com/o2.gif

Radiation at 254 nm is pretty 'hard' UV, and will be partly blocked by most plain glass, and certainly severely attenuated by the thickness of glass in the average lens.

 

Lenses using special glass are needed for ultraviolet photography - Medical Nikkors for example. Quartz glass is also needed for the envelopes of 'hard' UV mercury-vapour bulbs and tubes. The optical glasses used in normal lenses block it quite effectively.

 

The reduction of fungal spores by the UV in daylight during use of a lens must be almost immeasurably small compared to deliberate exposure under a biocidal UV lamp. Or keeping the lenses in a low-humidity environment.

 

And what about lens caps?

Aren't they 'dangerous' too?

 

FWIW, I found (the hard way) that lenses kept in leather cases tended to develop fungus much more readily than when kept in man-made materials. So it's not just a matter of humidity or lack of UV, but also keeping lenses away from materials and surfaces that can harbour and supply nutrients to fungal spores.

Edited February 11, 2021 by rodeo_joe|1

• UVC: ultrashort wavelength rays 200–290 nm blocked by Earth's atmosphere
  
• UVB: short-wavelength rays 290–320 nm blocked by window glass (also cause sunburns)
  
• UVA: longer wavelength rays 320–400 nm blocked mostly by the most obstructive Hoya UV filter
  

There is not much UV bouncing around below 290 to block. The least obstructive UV filter, produced by Tiffen, permitted rays of around 300nm to pass. Would either 290nm or 300nm UV pass through a camera lens?

The following experiments suggest UVC has more value in clearing lens fungus/bacteria.

Can a UV lamp kill fungus and make the lens safe for use? - Page 2 - PentaxForums.com

Very few glasses other than quartz transmit the short wave UV that kills pathogens and fungus. The short wave lamps use mercury and have most of their output at the 2537 angstrom resonance line which is a big eye hazard. In my early days doing chemical research I studied how radiation damaged organic molecules.

A blast of short wave UV would damage the compounds I was studying more than an intense gamma source as the UV was all absorbed.

 

Moist conditions promote fungus so keeping gear dry is best for prevention. Have heard of Thymol being used as a fungicide but have never used it myself.

Perhaps a small amount kept where you store cameras would help protect them, I don’t know. Leather cases are not the best things to keep your cameras in all the time as they seem to be one of the first places for fungus growth. A camera repairman I know told me about leather cases and suggested I ditch them for storage.

 

On Rangefinderforum there was a discussion by Roger Hicks on using Thymol to cure fungus, but I doubt it could penetrate lenses unless you used special techniques. Apparently museums have used it for fungus control on exhibits.

 

If a valuable lens is affected, disassembly and cleaning by an expert is definitely the way to go if it’s still salvageable, otherwise list it on eBay as mint. ;-)

... list it on eBay as mint. ;-)

Disgraceful. I have been caught out by people following your advice :mad:

Note the ;-)...... This was meant as humour as I know people actually do this and is why I NEVER buy ANYTHING used on eBay!

 

It was meant to be a warning to buyers and not advice of what to do!

It is OK to buy/use fungus infected telephoto lenses because at long zooms the deformation will be too small to detect on a pixel.

 

I have done more digging. Unfortunately the germination temperature of some fungi is higher than the lethal temperature for other fungi. I did not discover a temperature that the glass would need to reach to kill fungus, and there is a risk that raising the temperature might germinate fungi spores that had been dormant.

 

I wonder, however, if it possible to burn off fungi using a cheap laser pen because I read that the energy in cheap lasers can often be higher than in lasers with proper quality controls - apparently this can happen because invisible infrared emissions are sometimes dangerously uncontrolled in cheap laser pens. Has anyone tried that?

Yes, as far as I know the glass will absorb a lot of UV C, but maybe a tiny bit gets through.

 

I suspect that with sunlight it might be some visible light and some heat that gets to the fungus.