I just saved my polariser - it had been stuck to the adapter ring I use for most of my lenses.
Of course, I did a quick research on the internet. There are also nice youtube vids about this. My combination of methods found was the most practical to me. But whatever you do: NEVER USE PLIERS ON STUCK FILTERS! You´ll ruin your threads and probably scratch or break the glass!
It doesn´t matter whether the filter is stuck to a lens or to an adapter ring.
- a microfiber cloth as a working surface. A dishcloth or a towel will also do.
- a jar opener or a filter removal tool (you usually have only one, but will need two if you got filter and ring stuck together - this is only needed when you have a stuck ring because your hand can grab a lens nicely without tools.)
- some device to recreate the original conditions. My filter got stuck on a hot day, so I used a hairdryer to considerably warm things up. If stuck on a cold day, put things in the freezer for some time. Generally, any temperature warp in the materials will help!
- a (rather soft) rubberised cord. I used a piece of RCA cable, soft and sturdy.
Should you NOT have any jar opener or whatever means of grabbing, you can also press the whole combo filter down against your yoga mat. This´ll apply good grip. Of course, as in my case, with a polariser this won´t work, because it´s a revolving filter that won´t transmit any torque to the stuck thread.
2. grab the lens with your hand or grab the ring with the jar opener. DON´T GRAB THE FILTER WITH A METAL JAR OPENER JUST BECAUSE THE RING IS CHEAPER TO REPLACE!
3. sling the cord around the filter and hold it firm so you can apply grip. With a polariser, of course, only grip the checkered thread ring, not the revolving ring.
4. twist, et voilà!
Resume: Heat and careful appliance of torque did the trick for me and it´ll do even better if there are threads of metal and plastic involved. Just be careful not to break or scratch anything. The soft rubberized RCA cord was perfect for grabbing and twisting the ring.
Forget the rubber band methods. With a cable or cord you can apply all the force you need much more elegantly.