[c.a.m]

I run a 20 enlarger darkroom that is problematic for the enlarging lenses and electronic timers. Air conditioning helps to keep the air relatively dry, but when the darkroom is closed and no one is around, I run an ionizer and ozone generator...at minimum settings. When the darkroom is occupied, both are turned off.

Our air circulation also has a UV light cleaning system which helps. With all of this, I still see fungus but it does delay the problem considerably.

Interesting. Do you know what the average relative humidity is in your facility? My understanding is that fungus needs a relative humidity of greater than 70% to thrive.

- Craig

[Serkevan]

relative humidity of greater than 70% to thrive.

- Craig

Relative humidity is... well, very relative. The water content of 70% RH air at 30ºC is 3.5 times higher than 10ºC air at the same relative humidity - which is why tropical climates are so problematic; there's a lot of water in the air.

I'm not sure how fungus grows exactly, but the 70% might work as a general threshold because that's more or less when you can expect water to partially condense with small temperature changes (I guess the small condensation droplets are what lets fungus thrive?) but I suppose the effect depends on the temperature as well.

[c.a.m]

I'm not sure how fungus grows exactly, but the 70% might work as a general threshold because that's more or less when you can expect water to partially condense with small temperature changes (I guess the small condensation droplets are what lets fungus thrive?) but I suppose the effect depends on the temperature as well.

I'm not a fungus expert, so I researched the topic a while ago. This thread refers to a couple of papers, including a 1961 study:

Environments favourable to Fungus - PentaxForums.com

- Craig

[Serkevan]

I'm not a fungus expert, so I researched the topic a while ago. This thread refers to a couple of papers, including a 1961 study:

Environments favourable to Fungus - PentaxForums.com

- Craig

So at lower temperatures there is retardation under 85% RH (many fungi just don't germinate under that value at 15ºC) and 90%+ is enough to get the spores to germinate even at 10ºC. Makes sense that it's the presence of water droplets after all (or just the detection of water in the environment). I suppose that the fungus propagation is faster at higher temperatures, but that's probably because of the faster metabolism than the access to water.

Thanks for the link!

[Alex645]

Interesting. Do you know what the average relative humidity is in your facility? My understanding is that fungus needs a relative humidity of greater than 70% to thrive.

Relative humidity is... well, very relative. The water content of 70% RH air at 30ºC is 3.5 times higher than 10ºC air at the same relative humidity - which is why tropical climates are so problematic; there's a lot of water in the air.

The relative humidity in our darkroom fluctuates but is around 64% on average plus or minus 10%. For the chems in our hot climate, we run a ductless split air conditioner 24/7, but the air ventilation which imports 100% fresh outside air and exhausts 100% interior air (hood over the wet side) runs only 10 hours per day during occupancy. Because we do not recirculate the air in the darkroom due to chemical vapors, the outside air has an influence on our climate control.

It is even further complicated because unlike the ductless split air condition for the darkroom, we also get cool air thru ceiling ducts 10 hours per day, 6 days per week from an ice chiller plant. Although there is UV treatment of the air, blowing air over ice puts more moisture in the air than a traditional ac system.

For years, we were in a basement and the humidity was so bad, we ran a huge industrial dehumidifier. Now I'm on the top floor of a three story building and the only recent issues have been from compromises in the roof due to recent solar PV installations.

Most of the time we have 'cooler' trade winds, but perhaps a third of the days the wind stalls or worse, it reverses and we get a moist hot and humid wind from the south called a Kona wind. And then of course there are seasonal changes. June thru November we enter hurricane season with our driest months from April thru October, and the rainy season is typically from November thru March.

So without unlimited funds and control of our lab, I cannot eliminate fungus; it's more abatement and management.

[Theov39]

My dad was an engineer specializing in optical instruments and one thing he told me is to never store lenses (or any optical gear) in leather cases or bags. Leather, being an organic material really attracts fungus and mold. So I guess all those old 'vintage' cases are out!

It's probably best not to store camera gear in any bags. Best to just have it sitting on a shelf (if in an area of relative low humidity) or, even better, in a humidity controlled cabinet. That is the most expensive solution but the most effective. I live in a semi tropical area but since doing that I haven't lost any lenses to fungus while before I lost a few.