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12-05-2010, 06:44 PM   #1
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M42 S-M-C Takumar 50/1.4: Fungus Favorite?

I have a bunch of lenses, old and new, stored in a box full of charcoal and silica gel desiccant bags.

Among all of them, the M42 S-M-C 50/1.4 seem to attract fungus the most. I have two of these, the one with the rubber grip and the older, all-metal one. I left it for the weekend without my lens cleaning routine and the rubber grip one got attacked by fungus on the inside, the other one just on the surface elements! The other lenses seem to be ok.

Are you also experiencing more fungus attraction on some lenses more than others?

12-05-2010, 07:01 PM   #2
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Charcoal, if freshly made, can be a dessicant but it can also store a LOT of moisture if the outside humidity is low. Do your silica bags have an indicator? Some turn blue or purple when they are saturated with water, but most of the little freebie ones do not. So if your silica gel is saturated and the charcoal is damp (IE if the pallet ever got damp or left outside in the rain) then your humidity may not be as low as you think it is! You can get cheap humidor hygrometer or pet stores sell them for reptile care.


There are two methods used for re-drying silica gel. One method uses the oven, and the other uses the microwave. Before you use either method, please read all the safety precautions described below:

Oven drying method: This method gives the best results even though it takes longer. Set the oven for 275F. Place the silica gel in an appropriate container and dry the gel until it turns medium blue. The oven drying method takes approximately 1-1/2 hours per quart of gel. One quart of gel weighs approximately 1.9 lbs (30 ounces).

Microwave drying method: Place the silica gel in an appropriate container and set the microwave power to the medium to medium-high setting. Dry for approximately 3 to 5 minutes and inspect the gel for color change. If the gel has not dried, stir it with a spoon and heat it for another 3 to 5 minutes. Stir the gel each time it is inspected. Approximate drying time is 8 to 12 minutes per pound of gel. The actual heating times will vary according to the type of microwave. You may set the power setting on high but please be careful not to overheat the gel. "
12-05-2010, 10:09 PM   #3
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Join Date: Feb 2007
Location: Aurora, CO
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Some construction methods are more resistant to fungus. For example, this is an assembly from a Pentax-M 50mm f1.7, including the front and rear lens groups and the aperture:

It's not airtight, but the only significant connection with the outside world is the chrome piece marked with the arrow, which moves the blades. With some lenses, much more is exposed.

I solved all my fungal problems by moving to Colorado, which is practically like living in an airliner.

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