Join Date: Jan 2011
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Re: Replacing old, crazed (broken) windows
Acrylic is harder. It is less likely to break by a given blow but when it breaks it cracks. Lexan (polycarbonate) is not bullet proof but is more likely to deform under a blow. It's softer, scratches more easily, but it can be cold formed (like sheet metal). Enter IMA (impact modified acrylic). Not sure what they do but it gets closer to polycarbonate in impact resistance. 3/16 to 1/4" should be more than enough for you. 1/2" is unreasonable for most applications unless you're be walking on it or it the thickness is mimicking some other material (ie teak). Actually, if you'll be reusing the gaskets, you're limited to the range its designed for anyway. I will say that either you or the PO has most likely been using glass cleaner on those portlights. They appear to be badly crazed. You should NEVER use ANY type of glass cleaner on plastic of any sort, especially windows and skylights. The ammonia and other chemicals cause plasticizer migration resulting in the crazing I see. Just use dish soap, nothing else.
I designed commercial, residential, architectural and monumental skylights for 18 years. Currently I am a high end window designer.