What is the acceptable relative humidity level for mixing and applying epoxy?

The ideal relative humidity for mixing and applying epoxy is less than 50-60%, but epoxy can be applied up to 80-85%. Applying epoxy under high relative humidity conditions creates a much higher risk of a poor surface finish. Care should also be taken to ensure no moisture is sitting on the substrate directly before applying epoxy under humid conditions, to promote the best bond. Mixing epoxy under extremely high humidity, or epoxy that was stored under high relative humidity could seem hazy and lose clarity.