[codazoda]

A contractor showed me how to fix dents in granite with superglue. It’s totally clear. The trick is to scrape it with a razor blade at a 90 degree angle (strait horizontal). The imperfections become nearly invisible.

[dlcarrier]

This is also how glass chip repair works. If the polymer has a close enough index of refraction to the glass, it's invisible.

[MisterTea]

I've been told this is a cheap way to fix small windshield cracks. Never tried it but sounds like it would work for the small spider sized and shaped cracks from small rock impacts.

[tjohns]

This is basically what the glass repair kits sold at auto parts stores are. (They also include a suction cup with syringe, to vacuum any air bubbles out.)

[coryrc]

And, bringing this topic full circle, the chemical in those kits is methyl methacrylate!

[singleshot_]

The expensive way is superglue plus a little suction cup to evacuate the air, and a razor blade.

[dlcarrier]

The rule of thumb is that if the damage fits under a US quarter, it'll work for sure, and if it fits under a dollar bill, it's worth a try.