[garof]

It also makes me think of sticking two clean pieces of (optical) glass together without glue: https://en.wikipedia.org/wiki/Optical_contact_bonding

[TheSpiceIsLife]

This would be the same phenomenon that causes guage blocks to stick together, I presume?

[garof]

Not sure. Contact bonding can be strong enough to pull chunks out of one or the other of the glass pieces when you try to separate them. I've not personally seen this happen, only the results.