Effect of Temperature on Mold Making and Casting

Temperature can play havoc with the curing of molds and casts by delaying/accelerating the process or not allowing the material to cure at all. Knowledge of the properties will ensure better results.

It is not just about the technique or dexterity of the artist; the quality of the mold or cast is affected by many other characteristics as well. Temperature plays a starring role here – ranging from the temperature and humidity of the surroundings to even the warmth/coldness of the material and model/mold.

This is why it is always recommended that all rubber and resin compounds should be stored at room temperature (72°F/23°C). For instance, if a material is stored at elevated temperatures, like in a hot garage or in direct sunlight, both the shelf life and pot time will get reduced drastically. In contrast, if latex rubber freezes, it becomes unusable and has to be thrown away. Other frozen materials can still be used after they are brought back to room temperature.
Let us take a look at how the temperature factors can affect the making of molds and casts:

Cold – A cold environment will usually prolong both the working time and cure time of most materials like epoxy resins, urethane rubbers and platinum cure silicones. The evaporation process of latex rubber also gets delayed in colder temperatures. In case the environment is too cold, some of these materials may even fail to cure at all. However, tin-cured silicones are not as dramatically affected by colder temperatures.

Heat – The opposite is also true as higher temperatures are known to accelerate the cure time and most materials tend to cure much more quickly when it is hot. In fact, many artists deliberately apply heat to hasten the curing process. However, tin-cured silicone rubbers are again an exception as they are not as affected by heat and cannot be ‘heat cured’.

Humidity – Rubbers are best used in a low humidity environment. Higher humidity tends to accelerate the curing in tin-cured silicone rubbers while it has the opposite effect of slowing the evaporation and curing process in latex rubbers. Making molds or casts of urethane rubbers, plastics or foams in humid environments can cause bubbles or foaming in the material. However, platinum-cured silicones and epoxy materials are not affected by humidity.

In addition to this, if the model that is being used to make the mold happens to be too cold, the curing of the mold will take unnecessarily longer to cure and vice versa. Therefore, the model/mold should be brought to room temperature prior to use. When making a mold of a frozen model, it will start condensing once the mold material is applied which will in turn delay the curing. This is why it is better to use accelerated silicones as they will not be affected by the moisture.

Finally, good quality liquid latex rubber, silicone or epoxy materials can be easily sourced from EnvironMolds at https://www.artmolds.com/ at the most reasonable prices.

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