Try goo be gone.

I've done it. Make the same kind of soap solution that is used when it's put on. Maybe make it a little stronger...1 t dish soap into a spray bottle. Spray liberally, very wet. Put cling wrap all around the window surface (overlapping), a couple of layers if needed to so the solution stays wet. The soap will go through the film and will release the adhesive. It has to soak for 2+ hours (1 hour will release some but 2 is much better). Make sure that it cannot dry. You still have to lift a corner with a razor but you will be able to pull it off in large sections. I know the nightmare removing old, crusty film can be...it's horrible.

What luckyblueeye said -- I have film on my window and this is exactly what I plan to do with -- the problem in the OP is that it is crumbling but putting the plastic wrap on and keeping it wet might do the trick. Article I read recommends Dawn dish soap

Thank you for suggestions! Goo Gone and razor blade worked perfect!

Nikkey Love

Thank you for suggestions! Goo Gone and razor blade worked perfect!

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great! I am going to do the spray technicque but it's good to know that this will work if I need a follow up.