As we get thrown into the summer in the UK we wanted to talk to you about transitioning to using Craft Resin’s Epoxy Resin when temperatures get warmer and humidity rises.
The ideal temperature when working with Craft Resin is between 70-75F or 21-24C. Which is great as many indoor spaces can reach this in the summer times, but what happens when it goes past this temperature, you might need to make a few adjustments to your techniques.
One of the most common effects we see when temperatures rise and humidity increases is Amine Blushing.
Amine Blushing is when your resin cures with a strange texture on the top of it, it can look like an uneven coating or like it has water marks or a crackling pattern in it. Sometimes it can hardly be seen, other times it is more visible.
Amine blushing can be caused by moisture in the air or humidity in your workspace. A drop in room temperature during the curing process, or the room being too cold in general. These cause the water soluble components of the resin to rise up to the surface and leave marks behind.
So for example if you are creating your resin art during the day and the temperature is a beautiful 24C, then that’s great, your mixture should be a great consistency and any micro bubbles should disperse before your eyes. But then you leave your work to cure over night, and the temperature drops rapidly, this is when this can occur.
How to prevent amine blushing from happening:
1 - Keeping the room temperature warm, between 70-75F or 21-24C as a minimum.
2 - Ensuring your workspace has a maximum humidity of 85%. A humidifier gage can help monitor this and if the humidity is above 85% you can get a dehumidifier to help control this.
3 - If your workspace is too cold, you could try something like placing your work by a fan heater.
You can also fix amine blushing on your cured pieces by either buffing and polishing your piece or if that doesn’t work, gently sanding your piece and adding another clear topcoat of resin.
Note: Make sure this top coat doesn’t get cured in the same environment as before, keep the temperature constant, or it will happen to this layer too).
The image below shows a slight amine blushing taking place, sometimes they can be very hard to spot unless you catch it in a certain light, other times it's more visible.
If you’re used to warming the resin in a warm bath before mixing in the cooler months, consider skipping this step if your products are already warm.
When the temperature rises you may have to consider controlling the exothermic reaction that occurs when you mix the resin and hardener together.
Once you combine the craft resin and hardener, a chemical reaction starts to happen that starts 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 crystal clear epoxy resin that you use.
⚠️PLEASE NOTE: When mixing large batches of resin and hardener, pot life— or the amount of time that elapses before the epoxy resin hardens in the container—is very important. You need to estimate how much mixed clear 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 resin epoxy, spread it over a larger surface area, work in a cooler environment, or mix multiple, smaller batches as you go.
The chemical reaction between the resin and hardener as epoxy cures will generate heat. When this heat cannot escape, it builds up, causing the epoxy craft to cure faster because epoxy dries out 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 Craft Resin 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 resin heating out of control can foam, smoke, give off dangerous vapours 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.
The mechanism that causes heat buildup when epoxy resin is contained in a thick mass also causes the epoxy to take longer to cure when applied as a thin film. The film does not build heat, so the temperature through the thickness of the epoxy film is pretty close to the ambient temperature.
Occasionally customers are interested in filling a void by pouring a large mass of epoxy resin all at once. This can be very dangerous because it will generate a lot of heat, and can lead to poor results because of the snowball effect mentioned earlier.
Pouring a large mass of epoxy resin is very difficult to do safely and effectively. Temperature, volume of epoxy, depth of the clear epoxy, and amount of heat sink in contact with the epoxy are all major variables in this process.
Proven methods for controlling exotherm:
If you do want to pour or cast a large volume of resin epoxy, here are several proven methods for minimising heat buildup those we've been developing for years.
Pour the clear epoxy in timed, multiple batches:
Timing is important when doing multiple pours. Ideally, you need 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 up and cracks to propagate.
Work at cooler temperatures:
Cooler workshop temperatures and cooling the epoxy resin itself will both work to your advantage in slowing cure and controlling the epoxy’s exothermic reaction. A deeper pour can be accomplished with less heat build up by starting with cooled craft 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.
Displaying your resin work in hotter areas:
The other thing to consider when the temperature increases is to watch out for where you are displaying your cured resin pieces. If you display them in a room that gets very hot, for example a conservatory, which is also surrounded by glass and therefore in direct sunlight, your resin pieces can become flexible. Once the pieces cool down again they will return to normal and will be hard again.
If you are going to be displaying your resin in warmer temperatures do think about where you will be putting them, and advise your customers to do the same too.
As with most techniques in the resin world, a lot depends on various factors like the environment you are working in, the temperature over the whole process, the amount of time the resin and hardener is mixed for, the amount you’re mixing together and what you’re adding to it to name a few.
When it comes to a change in season and temperature, then you may need to experiment with your techniques and adapt as required. Just because you were using a certain method that was working really well for you in one season, doesn’t mean it will work in all of them.
Team Craft Resin