Why is my CPL so hard to clean?!

Some are easier to clean than others.
Funny I have the worst time w/ cleaning Hoya's HD polarizers. The Pro-1 & B+W filters weren't as bad.

Its probably a hoya.. I prefer Marumi- better build, easier to clean and according to the CPL comparison at lenstip still top quality, or B+W MRC if i can get it at a fair price.

For cleaning I use *reagent grade* methanol (eclipse) and pec-pads, I bought one set years ago and still have plenty left (have used on sensors too).

cold tap water & Dial hand soap !!! works for me

swolfcg wrote in post #10321626
Some are easier to clean than others.
Funny I have the worst time w/ cleaning Hoya's HD polarizers. The Pro-1 & B+W filters weren't as bad.

I have no idea how you can have a tough time with the hoya HD's...I can wipe them on my shirt and they'll be clean as can be. Pro-1 was a nightmare.

Like I mentioned earlier, I've been using "Formula MC" and lens tissues for decades. Hasn't been anything it didn't clean easily. Even those plastic Cokins and SLR mirrors.