[stoppingdown]

Yesterday I performed the periodic review and clean up of all my equipment and discovered a bad surprise: two B+W polarisers have been infiltrated by moisture inside the two glass elements. I don't think it's feasible, anyway I'm going to ask: is it possible to disassemble and reassemble the two glass element at home?

[photonius]

I wouldn't try. Probably you damage the thin sandwiched polarisation layers. Are you even sure it's moisture in there? If it's really plain humidity in there, maybe you can try to dry it in a desiccator?

[stoppingdown]

Probably you damage the thin sandwiched polarisation layers.

Yes, as I supposed. So let's repurpose this thread to understand what happened.


Looking with a magnifier lens I'm seeing that there are no tiny droplets of water as I supposed (so it's already dry), but a web of linear segments. It could be water that evaporated and left salt crystals. The plot thickens, as I don't think condensation water contain salt. I'll post a macro photo of it later.

[stoppingdown]

Here we go with the photo...

[toni-a]

Bring here to qatar, put it outside for 10 minutes, I assure you any trace of water or humidity will go.... just kidding, easiest thing: put it outside in the sun for a day, any moisture should go

[stoppingdown]

It's already dry — what you can see is the residual stuff after evaporation. I really can't understand what happened: all of the other filters in the same poach (which does contain moisture absorbing bags) are fine. And five minutes ago I discovered that the 77mm B+W polariser ended in the same way, despite from the fact that it has been stored at home for 8 years, no more used after the last Nikkor lens was replaced.

[photonius]

looks odd. I am wildly speculating here. Some of the polarisation material may be composed of liquid crystals in some polymer, it seems to be basically something like a thin, stretched plastic film. Maybe it cystalized, polymer went bad? Did some fungus grow there into the polymer, causing damage and crystallisation?

[stoppingdown]

B+W filters are distinguished from all the others by two things:

1. a plastic box that is “almost” sealed when closed;
   
2. a polystirene (or such) padding inside — I noted that at least a filter was partially sticked to it.
   

So I'm thinking of something like a fungus too, which perhaps developed because the boxes have been kept closed for years.

[toni-a]

Sometimes we see issues on the glass but surprisingly they don't affect the optical performance.
Did you test the polarizer to verify if functioning is affected ?

[stoppingdown]

I'd like to do that, but first I want to exclude the possibility of fungus; if it's a fungus I want to keep it at a distance from the other pieces of the equipment.

---

I've done a bit of research, but unfortunately there are just very few images of polarising filters affected by fungus (notably one guy had his Sing-Ray [ouch] filter affected: https://www.dpreview.com/forums/thread/3358596). But I think that what I'm seeing are both residual of water evaporation (in shape of particles) and pieces of fungus (in shape of segments).

I couldn't be able to guess when those polarisers were last used, with the exception of the 77mm, November 2011: a couple of years later I moved from Nikon to Sony and that filter was no more used, being no more compatible with the new system lenses. It's likely that the other two filters weren't used much more recently — so it's more than ten years.

I think that the problem was probably caused by the fact that B+W filters were stored in their plastic cases that are more or less sealed. Probably I opened them for a periodic clean up in a day with high humidity, then closed the cases; humidity got trapped; then temperature dropped, water condensed into droplets that found their way inside the junction. Actually traces are in form of a uniformly thick ring near the border. Water allowed fungi to develop. This scenario is a bit forced, but I can't imagine anything better.