Does Temperature and Humidity Affect The Mould Making And Casting Curing Process?

Yes, cooler temperatures will slow down the curing process, (may not cure at all < 60 degrees F / 15.5 degrees C) and warmer temperatures will speed it up. High humidity can also affect the curing process.

Tin Cured Silicones

Tin Cured Silicones are condensation cured, so high humidity will speed up the cure on the surface that is exposed to the air, while the internal part of the mould remains liquid. Don’t let this fool you into thinking the entire mould is cured.

Platinum Cured Silicones

Platinum Cured Silicones are generally not affected by high humidity.

Polyurethanes

Polyurethanes are very sensitive to humidity. It can cause bubbles or foaming in the cast part. Additionally, the containers of liquid Part A and Part B can accumulate moisture from high humidity over time. This is why it is important to keep the containers sealed when they’re not being used. Part A will actually cure from the moisture in the air and form a crusty material around the lid. Part B may look okay, but it still may have moisture in it. If you see a lot of bubbles in a cast urethane part that are not created by air trapped in the undercuts of the mould, or air that is whipped in by mixing too fast, it’s likely to be from moisture.

TIP: Refer to Technical Bulletins or Datasheets before use. Use heat lamps to help the cure at lower temperatures.

Original Source: Polytek Development Corp.