Cleaning a polarizer filter should only be done if image quality is being impacted. So how do you clean a polarizer filter?
Rocket blower to remove the dust and any debris. Lens cleaning solution to remove the smudge. Kimwipes to clean the element. Let me repeat it don’t clean the filter unless it is causing issues. Everything you need can be purchased at Amazon, BHPhoto, or Adorama.
Many of the polarizers have a special coating that can easily be damaged if you are not careful. For example, B+W filters have a Multi-Resistant Coating to help the lens stay clean longer. The more you clean these filters, the more likely you are to damage the coating or scratch the glass.
I recommend buying a high-quality polarizer like the B+W with a resistant coating to help minimize the need to clean your filters.
1 – The first step should be to use your Giottos Rocket Blaster, the knock off blowers that I have encountered do not have the same force. Please do yourself a favor and grab a Giottos. If you have a DataVac blower, these work well, make sure your filter is not attached to a lens and is secure. If it is connected to a lens, you can damage the len.
2 – Next, use a clean lens pen. I would buy one pen for your filters and not to be used for the viewfinder, rear screen, or eyeglasses. You can actually end up transferring oil inadvertently from your viewfinder to your filter. I know from experience.
3 – Still not clean? Pre moisten Zeiss lens wipes are the next step. Make sure there is nothing on the lens that can scratch it like a piece of sand. Next, open the wipe and clean the smudge. Throw that wipe away and open a new one and clean the filter until all the alcohol has evaporated.
4 – I usually skip step three and use this step instead. Grab a bottle of Zeiss lens cleaner and Kimwipes, which are sometimes called Kimtech wipes. You can pick these up on Amazon, BH, or Adorama. Spray the clean on one side of the filter and let it sit for 30 seconds. Then wipe until dry.
Nothing is working; please help? Ok, if none of the above are working, I would use dawn dish soap. It is excellent at removing oil and has saved me a few times. I just wet the filter then rub the dawn around with my finger. Wash the filter with clean flowing water making sure not to allow the water to enter between the two layers of glass. The filters are well sealed, I would avoid submersion or pressure.
Here is a post from Roger Cicala at Lens Rentals if you are looking for a second opinion. Without a doubt, he has more experience cleaning lens than me!