How long should a silicone mould cure before demoulding

The guide times in product documentation apply to ideal conditions and to a single poured layer. In a brush on mould you build several layers, and the bottom layer was applied first but cures through last, because it is the least accessible to air and moisture. So deliberately allow extra time.

Wait at least twenty four hours before taking the mould off the original. At low temperature, low humidity or with a thick build up, wait forty eight hours. Full final strength and tear resistance is only reached after three to seven days.

Demoulding too early is one of the most common causes of a failed mould. If the bottom layer has not cured through, that layer is still soft and liquid. As soon as you release the mould and stand it upright, that material flows out and the sharp detail of the original is lost. This cannot be recovered.

Work at eighteen to twenty five degrees and at a relative humidity of forty to seventy percent. Condensation silicones need atmospheric moisture to cure, so in a dry and cold room it takes considerably longer than the stated time.

Do not load the mould heavily in the first days and do not yet cast heavy or strongly exothermic materials.

Read more: complete guide to making a brush on silicone mould