To be comfortable with the slow curing time of epoxy casting resins, it’s helpful to understand a little of the chemistry which controls the epoxy resin curing reaction. The reaction that hardens these resins emits no chemicals during the process. The only byproduct is heat. The larger the amount of resin and hardener that is mixed or poured, the more heat that is created during curing.
The creation of too much heat can discolor or even crack the pour as it hardens. This can ruin the final appearance of products like Mirrorcast™ and Rivercast™, which almost always makes the time, effort, and money spent on the project wasted. To avoid this situation, we’ve formulated these products to contain few or no materials which create excess heat. Unfortunately, these are the very materials that contribute to faster resin hardening.
The inconvenient consequence of this is that curing takes place slowly, often stretching into days instead of hours. But the good news is that they do cure crystal clear, very hard and tough, and with virtually no shrinkage.
For further information on epoxy curing chemistry see: Epoxy Book Section III.