Epoxy systems are systems that dry by the combination reaction of epoxy resin and epoxy hardener. In order for this reaction to start, the resin and hardener must come together and this meeting initiates the reaction process. The homogeneous mixing of the products with each other successfully terminates the process and the epoxy drying occurs.
The case that the drying is in partial regions or not in partial regions is completely related to the mixing of the system. You can review our article titled “How to Make Epoxy Mixture” for details that need to be considered.