Aleš Lombergar

As always, there is some real physics at work here. Most stuff, glass, metal, you and me, are held together by van der Waals forces. These are forces caused by asymmetry in molecules. Even though these forces are strong enough to hold things together, they are very short range. If the molecules are separated by even a tiny amount, the forces are too weak to hold things together. If you can get stuff close enough together again it will weld back together. This happens with high precision surfaces especially in vacuum chambers where you actually need to be careful that things won’t weld together on contact.

As far as broken glass, there is air, dust, chips of glass, etc. that interferes with the very, very close contact needed for the material to reattach. For what it’s worth, even glue works using van der Waals forces, it smears over the surface making good enough contact for the forces to help hold stuff together.

I think you don’t need any physics explanations for this…
Its simple… glass is solid and when some solid particle breaks it can only be reunited using some other stuff like glue… but reuniting them without anything is impossible… Is is the law of Nature and we have accept it….. ^_^

The pieces of glass can be melted together and recast into a new glass.

glass is made up on silica corbonates and sodium carbonates and they are joined by overcoming there valency eg silica has vacant d orbital and it uses that for joining but if you break it then there polymeric chain get’s broken and it is difficult to join them.

ok! so what is the answer…..can glass be reunited OR not!…if it can be, then can it be made to acquire the same shape,size..