One unfortunate side-effect of living in a basement flat by the sea is the damp. Over the course of the last few years this has taken its toll on my lenses, they all show traces of mould or hazing. Fortunately, after closer inspection, on two of the lenses the damage was restricted to the external elements so could be removed by some careful cleaning. The remaining two (50mm and 110mm macro) clearly had issues on the internal surfaces as well.
I had a few options: just ignore it (often the effect on the image is negligible), get them professionally cleaned, or do it myself. While weighing up my options I found this excellent guide by M.Vettore: Disassembly a ZENZA BRONICA ZENZANON 150/4 PS Lens. It gives clear instructions for each step of the disassembly/reassembly and recommends the tools required for the job. The main things required are rubber cones, a spanner wrench, and small screwdriver. I purchased the spanner wrench from ebay for about £20. The rubber cones and screwdriver were far better value from Micro-Tools in Germany even allowing for shipping.
Step 1: Remove the front ring.
On some lenses you might be able to remove this by hand but the rubber cones make it much easier. Simply select one the right size and twist off the ring.
Step 2: Extract the front element group
In the 110mm macro this group is quite deep inside the lens barrel. I place a small square of lens cloth over the glass just in case my hands slipped and used the spanner wrench to unscrew the group. Once it was loose I faced the problem of how to remove the group from inside the barrel. I couldn’t get my fingers down inside and I didn’t want to just up-end the lens and tip them out. Fortunately my wife is adept with a pair of chopsticks and she managed to lift them cleanly from the barrel.
With the lens group out the aperture electronics and rear elements can be seen. It was also clear that the mould was only present on the rear surface of the front lens group so no further disassembly was required.
Step 3: Removing the mould
The coatings on internal lens elements can be very fragile so care is required for cleaning. The recommended process is:
a) Blow off loose debris with an air blower, I use a Giottos Rocket
b) Use distilled water only, with a swab or lens wipe.
c) If that does not remove it, try distilled water with some detergent in it. I use Ilford Ilfotol wetting agent as it’s designed for use with film so should be mild and free from unnecessary additives.
d) Then if that doesn’t work use a solvent based cleaner.
I had to go to option (d) as the mould was very stubborn. The mixture I used was 70% Isopropyl alcohol, 30% distilled water, and a few drops of Ilfotol. There was a risk this would damage the lens coating but in the end it worked just fine.
Reassembly is the reverse of the disassembly process making sure everything is seated properly and nipped up tight.
The lens is now crystal clear and shoots perfectly. I had hoped to repeat this process on the 50mm lens. In this case it is the rear group that is damaged. Unfortunately I have been unable to remove the group as it is in very tight (or secured with thread locking). The risk of slipping while applying enough force and damaging the lens is too great so for now I’m shooting with the lens as-is. If the mould gets much worse and starts to seriously affect the image then I’ll have another go.