How does Epoxy resin work?

Resin is a polymer, which means it is made up of long chains of molecules that are bonded together. These molecules are called monomers. When the resin is mixed with a hardener a chemical reaction occurs that causes the monomers to link together and form a solid.

The hardener acts as a catalyst. It speeds up the chemical reaction and ensures that the resin cures or hardens properly. Curing times vary depending on which type of resin is used. For the Epoxy resin I use, curing times are typically 24-72 hours. Generally, the higher the maximum casting thickness of the resin, the longer it takes to cure. The resin will also take longer to cure in colder temperatures.

Reference: https://www.mouldd.co.uk/blogs/news/what-is-resin-and-how-does-it-work