Using Epoxy, Polyester or Vinyl Ester Resins in Cold Weather

Winter is coming and the temperatures are dropping. In some areas there will be sub-zero temps. Does this mean that your epoxy resin projects will have to wait until Spring? Maybe, but most of the time that is not the case. You can still have a successful project, with a little extra planning and following some specific guidelines.
First off let’s discuss how the colder temperatures can adversely affect epoxy resin. When working with resin, it is recommended to work in room temperature of at least 72 degrees (72 to 90 degrees). If the room is colder than this, the curing time will slow down considerably and the part may not cure at all. It is important to note that your project will take longer than usual to complete.

The colder weather can cause the epoxy resin to become more viscous/ thick. This makes it difficult to accurately measure and mix the resin and hardener. It will take more effort to blend the two together and there is a chance there will be less of a chemical reaction. The epoxy will be harder to apply as well. There could be uneven coats that will require more sanding. This can lead to air bubbles or fish eyes which are very undesirable. Not only are they unsightly but they reduce the strength of the bond.

In some areas, the colder weather can bring more humidity. This humidity creates excess moisture that can settle on your project and affect the bond and curing of the epoxy applied to it. This unevenness can cause amine blush, surface defects and reduced shine.

Tips for Using Epoxy Resin in Colder Temperatures

With all that being said, there are ways to prevent these adverse effects. A successful project can still happen even in colder temperatures. It will just take a little additional planning and preparation.

Remember that when the product shows up on your freezing doorstep you will need to warm it up to room temperature. Bring it inside to a 72 degree room or warmer and let it warm up for several hours if not longer. If you are in a hurry you can use space heaters and/or heat lamps. Thermostats for heaters can be slightly off so you may want to turn it up a few degrees to ere on the side of caution. (Do not use open flame heaters). Another option is to use a warm bath. Make sure to dry off the bottles before using the resin to prevent moisture from getting into resin or onto the project.

Use an infrared thermometer to ensure the resin is warm enough before mixing. The warmer resin will lower the viscosity/thickness. The thinner resin will mix and measure easier. It will also not cling to the containers as much as it would in a thicker state. This will get your project off to a good start.

Once the resin is warmed up to room temperature, you will want to make sure the bonding surface is warm as well. This will result in a better adherence between the surface and the resin. It is important to not use extra hardener to make up for the cooler temperatures. This can diminish the quality of the bond. You can warm the surface with heat guns or hair dryers.

Make sure your space is well ventilated. It will need to stay at 72 degrees or higher for the most ideal cure. This can be achieved by using a smaller space, making a warming box for the resin and materials and tenting the areas you are working in. A warming box can be created with rigid sheets of foil insulation and a light bulb. To tent the area, you can use several methods including using a thick plastic and even adding a heating blanket over top. Make sure the heating blanket is not too hot. No not leave equipment on or running while unattended. This includes heat lamps, heated blanket and space heaters. Never use open flame heaters, specifically ones that burn kerosene or fuel oil.

Make sure to prepare the surface in between epoxy resin coats. Since the colder temps, mixed with humidity, can cause amine blush, be sure to check for this. Amine blush is a waxy bi-product that can appear when epoxy cures slowly and will hinder the adhesion process. This waxy buildup can easily be removed with warm water. Use white paper towels to dry the surface.

You will need the area to be 72 degrees or warmer, not only before and during the process, but for several days after completing the project. The full curing process will take 72 hours so be prepared.

Once the epoxy resin has initially cured, raise the temperatures slightly. This will strengthen the resin bond. Do not raise temperatures before the initial cure. Once the resin has initially cured, slowly raise the temperature to avoid shock.

It is possible to work in temperatures lower than 72 degrees but the process will take a lot more time. A good rule of thumb is that for every 18 degrees Fahrenheit the temperature is under 70 degrees, the cure time doubles. If temps are below 72 degrees, mix the resin much longer before applying to your project- at least two minutes with mixer.

If you have leftover epoxy resin, store the epoxy resin in a warm spot. If your resin freezes or has crystals, you will want to give it a warm bath before using again. Follow the manufacturer’s instructions for storing your resin.

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