Ideal Conditions for Lens Fungus

About a couple months or so ago I picked up a Durst enlarger with a 50mm Rogonar for free. I've only recently set it up in my laundry room. Since then I've picked up a Meopta with a 50mm 2.8 El-Nikkor because it wasn't very expensive and came with everything else I needed to get set up.

I've made a few prints with the Durst. They were my first wet prints, and I was quite satisfied with it despite having a lot of trouble with using an easel and getting even borders. I decided to do the same prints with the El-Nikkor just to see if there was a noticeable difference between the two lenses, but as I removed the Rogonar I caught a glimpse of fungus in the lens. It was a lot worse under inspection.

Pictures for reference.

I'm not upset about it as it didn't cost me anything other than the fuel to drive to pick it up. I don't recall seeing fungus when I got it home. It was sitting by the window in my living room up until last week. I can't hep but wonder if this is something I might have caused. Did I pick a terrible place to set up a darkroom? It was the only reasonable place with running water I had access to.

I think many darkrooms are damp when water is about so that means many people have fungus forming in their lenses? I doubt but it could be a source.
You say it was lying at a window and only recently set up the enlarger in your darkroom. My guess it was there when you picked up the enlarger. You say the images were good so maybe it is not catastrophic and could be cleaned.

I'm hoping that this is the case as I don't want to inflict unnecessary damage unto the El-Nikkor. I'm fairly adventurous, so I plan to disassemble and clean the Rogonar. I'd imagine it must easier since there isn't much to go wrong with focusing elements and what not.

It is a very long time since my microbiology classes at medical school but fungus needs a food source (dust) and some moisture. You cannot eliminate dust (reasonably) so reduce the moisture ingress.

I store my enlarger lenses outside the darkroom in the hope that it minimizes the risk of fungus. I did have a Rodagon (bought new) grow significant fungus years ago before I started this practice.

Svenedin said:

It is a very long time since my microbiology classes at medical school but fungus needs a food source (dust) and some moisture. You cannot eliminate dust (reasonably) so reduce the moisture ingress.

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john_s said:

I store my enlarger lenses outside the darkroom in the hope that it minimizes the risk of fungus. I did have a Rodagon (bought new) grow significant fungus years ago before I started this practice.

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I had both of these in mind when storing the enlarger. After using it I decided to leave the lens on it to prevent dust settling in the enlarger with a garbage bag over it, but I can see why it'd be sensible to store lenses outside the darkroom. Forgive me, as I'm still quite new to this, self taught, and ignorant, but is it safe to leave the enlarger with a lens mounted? I can only assume there must be an enlarger body cap of sorts -- if not a generic Leica body cap.

The Rogonar was an inexpensive kit lens to begin with so it's not much of a loss.

There is a really strong chance the Rogonar already had the fungus there when you got it.
High humidity is a problem, but lack of ventilation is often a major contributor to that.
Try to improve the ventilation - both when you are using the room as a darkroom, and when you aren't.
It is often enough just to leave doors open when you don't need to keep that darkness in.

House said:

I had both of these in mind when storing the enlarger. After using it I decided to leave the lens on it to prevent dust settling in the enlarger with a garbage bag over it, but I can see why it'd be sensible to store lenses outside the darkroom. Forgive me, as I'm still quite new to this, self taught, and ignorant, but is it safe to leave the enlarger with a lens mounted? I can only assume there must be an enlarger body cap of sorts -- if not a generic Leica body cap.

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Yes you can leave the lens mounted. I don't know about a "body cap". I put a large plastic bag over my enlarger when not using it to reduce dust a bit. Lenses I'm not using I put back in their "Keepers" (plastic boxes with a base that the enlarging lens screws into)

Put the lens in direct sunlight for a few weeks to kill the fungus. Then see if the fungus can be removed. If there is too much damage, buy another enlarging lens they are not that expensive.

Fungus can only grow where moisture exists . The best prevention is to keep the humidity below 60% , Ideally at 50%.