I ordered a couple of samples of protective film to see if they were suitable for our multi-touch installation. You could imagine, if you heavily use multi-touch that the projection screen gets damaged, because it's a fragile material in most cases.
The criteria where that the material had to be very thin (0,25 mm or thinner) completely transparent, non glare, smooth to touch, a bit flexible and super scratch resistant. Where as I used my nails to try to carve the protective film.
The following 3 protective films from GE plastics, came back negative from the tests:
HP 40HDB 112 0.250mm lexan film
HP 60HDD 112 0.250mm lexan film
HP 92HDB 112 0.175mm lexan film
They basically all left carved scratches after the nail test as well as the fact that not all were smooth to touch or reflecting too much light.
Also the protective film from Vikuiti™ 3M protective Removable Film [ARMR200] came out negative. Even though one can scratch pretty hard without leaving marks, this material is reflecting a lot of light and from lamps on the ceiling.
I had also received some protective films from anyscreenprotector, but they seemed more like silicone rubber samples. Which of course was way too soft, because it wrinkles when you touch it. We are going to test if they work as a compliant surface overlay later on.