Water based modelling materials „harden“ through the drying process – i.e. through the removal of the water it contains. This is usually accomplished at room temperature by means of evaporation into the air, a process that, depending on the size of the model, can take at least 24 hours to fully complete. Any attempt to speed up the drying process of air-dried modelling materials by means of a microwave or baking oven is not recommended because the material will dry out at the surface thereby making it impossible for the water vapours on the interior to escape (diffuse) and this can lead to cracks, bubbles or even a complete deterioration of the object being formed.

Microwave-hardening modelling materials are also water-based. But these contain additional fillers, salts and evaporation retardants that prevent the outer surface from curing first in a microwave and therefore allow a thorough curing in a very short space of time (about 10 minutes for every 100 grams of material). Microwave-hardening modelling materials can also be air-dried.