Here's one for all the "experts". What's the FASTEST way to break glass (a lens) with temperature? Should...

Extreme cold, then extreme heat. Make sure you protect yourself from the broken glass though!

Extreme heat from room temperature should do it, and would be fastest as there is only one step. On the other hand, if you don't count the first heating step, then hot glass into cold water will be fastest

Why do you want to break a lens anyway?

In theory, yes, your idea of heat and cold is the way to make glass crack or break (unless it is borosilicate/Pyrex). I believe the small amount of mass (your lens) will cause you problems. the lens may not be a large enough mass to cause a lot of movement from coefficient of thermal expansion (CTE). the CTE of glass is about 4ppm. Metals are ~15ppm. plastics are generally >30ppm. In order to use CTE as the mode to break glass, one generally needs some surface area or volume to get the glass to move a lot.

I also wonder if your glass lens is really not glass. almost all of these now are molded with optical grade epoxy/anhydrides. Try hitting it with a handheld torch. My guess is that the lens will melt and start on fire....

Depends on if you want to break it all raggedy or in a straight line? Id heat it first then if that doesnt break it Id throw cold water on it, while its still hot but wear safety goggles.that should work. I cant figure out why heat is your only option, why not just hit it with a hammer? Hope youre not planning to take down any casino or bank cameras?? LOL!!!

If you are allowed to use only heat, yes your answer is right. I have done that withe a water glass. First I poured hot tea in it and then poured the tea out and placed the glas on the bottom of a marble fountain. The result was very quick and satisfactory.

Hey, maybe this will help...