How to clean a wet filter?

Question

I recently bought a few expensive filters (100x100mm / 100x150mm). After a session of shooting in the beach the filters got wet, one from a splash and the other seems to be a bit wet because of the humidity.

I cleaned them by wiping them gently with a microfiber cloth, but, I can see that it is not absolutely clean.

Considering sea water contains salt, I wonder if it's best to wash the filters with fresh water first, wait them to dry and then, if needed, clean them with the cloth.

I also got a cleaning liquid for my PC screen, which came with a microfiber cloth and it works like magic. Will it be wise to use it on the filters too?

In case it matters, my filters are: Lee big Stopper, Lee ND/GND, Lee Polarizer, Singh-Ray GND Reverse, so some are made of glass and the others resin.

Another question regarding this microfiber cloth. I have the original cases of the filters. Most of them look like this:

and the big stopper case is:

Is it better to wrap the filters with microfiber cloth or it's better to keep them as they are in the original cases?

Answer 1

Microfiber cloth tends to do a poor job of absorbing liquids. That is why your results trying to wipe down wet filters is less than satisfactory. Especially when salt water is involved I would do what you suggest: first rinse them with fresh water (maybe even a final rinse with distilled water to reduce the amount of impurities) and then after they are dry wipe away any remaining residue with an optical grade microfiber cloth.

My experience with LCD screen cleaning liquid is that it leaves a slight residue, so I would avoid that with filters or lenses. The cases your filters came in should provide enough protection for them.

Answer 2

I would recommend buying a small box of Kimwipes. These are square tissue-like micro-fiber cleaning wipes that are designed to tackle exactly the kind of problem your having. They are not the same as a microfiber cloth, which has loose, flexible microfibers that don't actually do a good job catching and removing materials from a surface. Kimwipes have a more rigid structure, so the fibers don't flex and simply wrap around grime on something like a filter. Instead, the structure is more sound, and is (on a microscopic scale) pitted and uneven, allowing the wipe to actively pick up and remove grime.

Kimwipes are scientific grade wipes, and in my experience leave a clean surface without scratches or any other kind of damage. I usually use them dry, no water, no cleaning solution. If you do need to use a cleaning solution, there are definitely some that are better than others. I've found that Purosol is excellent, doesn't leave any residue or streaking behind, requires very little in order to thoroughly clean a lens or filter, does not damage multicoatings, and requires minimal effort to clean up grime (very little pressure and not much in the way of repeat wiping.) IF you prefer not to use any kind of solution and a dry kimwipe isn't sufficient, then the best alternative would be distilled water.