Cure time is affected by temperature: warmer temperatures facilitate curing and colder temperatures slow curing.
Warm and dry conditions are best when when working with Craft Resin. The ideal working temperature is 75-85F or 24-30C with 50% humidity, but you can work with anything below 80%.
What happens if Craft Resin freezes?
If Craft Resin freezes in its liquid state, simply move it to a warm place and allow it return it to room temperature before using it. Once it returns to room temperature, it will perform and cure normally.
Once you’ve used it and it has cured, however, you will want to protect that piece from freezing. This is mainly due to the expansion and contraction that can happen to the substrate. For example, wood can expand and contract with the temperature, which adds stress to the cured Craft Resin coat and could cause it to crack.
Why does my mixture feel hot?
Once you combine the resin and hardener, a chemical reaction starts to happen that is the beginning of the curing process. As with many chemical reactions heat is a normal byproduct of this. Heat output is greater with the larger quantities of resin that you use.
⚠️PLEASE NOTE: When mixing larger batches of resin and hardener, pot life - or the amount of time that elapses before the epoxy hardens in the container is very important. You need to estimate how much mixed epoxy you will use in a certain amount of time. Variables that affect this calculation include temperature, volume, surface area.
Generally, for every 18°F increase in temperature, pot life is cut in half. To increase the pot life of a cup of mixed epoxy resin, spread it over a larger surface area, work in a cooler environment, or mix multiple, smaller batches as you go.
The chemical reaction between resin and hardener as epoxy cures will generate heat. When this heat cannot escape, it builds up, causing the epoxy to cure faster because epoxy cures faster at higher temperatures. Curing faster because of the heat, the epoxy generates even more heat, even faster. This snowball effect is why a gallon of epoxy mixed all at once will turn solid in about 5 minutes.
The resulting massive build up of heat can cause the cured epoxy to crack because of the temperature differential between the top and bottom of the container. This uncontrolled heat build-up is called uncontrolled exotherm. Epoxy heating out of control can foam, smoke, give off dangerous vapors and generate enough heat to melt its container or cause nearby items to catch fire. It’s crucial to understand epoxy’s exothermic curing reaction.
If you do want to pour or cast a large volume of epoxy, here are several proven methods for minimising heat buildup which we’ve developed over the years:
Pour the epoxy in timed, multiple batches. Timing is important when doing multiple pours. Ideally, you want to wait for mild exotherm to peak and begin falling before mixing a new batch and pouring. Waiting too long could cause an insufficient bond between the two pours. Not waiting long enough can cause too much heat to build and cracks to propagate.
Work at cooler temperatures. Cooler shop temperatures and cooling the epoxy itself will both work to your advantage in slowing cure and controlling epoxy’s exothermic reaction. A deeper pour can be accomplished with less heat buildup by starting with cooled epoxy and a cool substrate until the epoxy initially cures to a soft solid. Then you could expose it to room temp or higher to complete the cure.
What is Craft Resin's heat resistance?
The maximum temperature that cured Craft Resin can tolerate after 21 days of curing is 200F or 93C.
At temperatures as high as that, the cured pieces may become a little flexible but once they cool off, they will harden up once again. Typically, the heat generated from a hot mug will not damage the resin surface on a coaster.
TIP: No matter which colorant you choose, do not exceed 6% colorant to the total volume of Craft Resin as this will affect the delicate balance needed for the chemical reaction to occur properly and guaranteed heat resistance.
These guidelines work for our brands resin, Craft Resin, other brands information may vary so please do contact them directly to check their best practises when using other resin products.