Bubbles in resin

With a pressure pot

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Without

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Uncured silicone in stems

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Wispy/cloudy streaks in clear resin

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Resin too soft

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Resin too brittle

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Temperature issues

Most resins are fairly temperature sensitive, with most being formulated to work best at an ambient temperature of 73° F / 23° C. Too hot and the resin will cure too fast / unevenly, too cold and the resit will struggle to fully cure and may take much longer than the specified time.

The ideal situation is to cast in a climate controlled environment however this isnt always possible and there are some workarounds.

Hot environment

Most resins cure using a heat based chemical reaction, in a hot environment this will start much sooner giving you a much shorter pot life.

To give yourself a bit more time while filling your moulds you can cool the mixing cup using ice. Either a ziploc bag filled with ice or a plastic block underneath the mixing pot both work well to help lower the temperature of the resin.

Cold environment

In a cold environment many resin will struggle to reach the temperature required to start the chemical reaction - this can massively increase cure times. There are a few ways to combat this.

• Preheat the moulds - silicone moulds can be heated using a toaster oven (do not use an oven you use to cook food as any resin left on the moulds may release vapours into the oven) heating the moulds at 50-70c / 125-160f for 10 -15 minutes is sufficient.
• Heat the pressure pot - wrapping the pressure pot with a fermenting heat belt or a terrarium rubber heat mat can help bring the pressure pot temperature up to a more manageable range. A 30W heater is sufficient for a 10L pressure pot.
• Post cure the resin parts - Once demoulded if the resin parts are still soft putting them in a toaster oven at a low temperature of 50-70c / 125-160f can help harden them, the amount of time required for post cure will depend on the resin used.