Many people consider set and cure time to be the same. However, these terms cannot be used interchangeably as they do not merely mean when a material is dry to the touch. The difference is elucidated below.
Mold making and casting are specialized arts that are commonly used for reproducing a form. The mold captures the negative image of the model and forms the base for reproducing the cast. While how to make a mold or cast involves different materials and techniques, the common thread running through the processes is setting and curing.
Indeed, the instruction manual for mold making and casting will refer to set time and cure time at different junctures. Even the materials too stipulate the specific set and cure intervals that have to be followed carefully to ensure that the mold/cast works as desired.
What exactly is this set/cure time and what does it entail? Let’s find out more:
Set time – In simple terms, set time is the window it takes for a material to turn from liquid to solid state. Be it resin, rubber, plaster, clay, concrete or something else, the material will gradually start to stiffen and is no longer workable. The interval can range from 10 or 20 minutes to a couple of hours on the outside.
The instructions will usually specify that the next layer of the product can only be applied after the previous one has set. This is when the mold/cast will feel dry to the touch and can even be demolded, if required.
Cure time – Curing is a longer and more complex process as it involves a chemical reaction that gradually takes place over time. It is only after a material has cured properly that it can be safely exposed to water or moisture. Moreover, the mold/cast can be used only after it has cured. Usually, the mold/cast is demolded after it has set and left to cure. The curing window can range from a couple of hours to even a couple of days.
There are a lot of factors that affect the set and cure time of a material. Apart from the type of product, mixing and purity, even the temperature, humidity and other weather conditions play a role here. In fact, some of the one or two part molds and even casts may even fail to cure in the presence of humidity.
The set/cure time can be altered by the use of additives or even by manipulating the amount of catalyst/water that is mixed with the base product. Some artists play with the temperature and humidity in the environment to accelerate/delay the cure time as per their needs.
Therefore, setting is the initial drying process that happens rapidly as the water or moisture evaporates, leaving the mold/cast dry to the touch. Curing is a much slower process where chemical changes take place in the material before the mold/cast is ready for use. In case, a mold/cast is not allowed to cure/set properly, it may even become unusable!