Working with Epoxy in Cold Weather

Working with Epoxy in Cold Weather Working with Epoxy in Winter (Without Overheating Your Studio) When temperatures drop, epoxy behaves very differently. Instead of curing too fast and kicking off a big exotherm like in summer, cold conditions make resin thicker, slower to cure, and much more likely to trap bubbles. The good news: with a few simple adjustments, winter can actually be one of the best seasons to work with epoxy. Why cold epoxy is a problem Cold affects every part of the epoxy process: Thicker viscosity When epoxy is cold, it gets thick and syrupy, which makes it harder to measure, mix, and spread smoothly. Slower or incomplete cure Below the recommended working range (typically around the low-70s Fahrenheit and up, depending on the system), cure time can double or even stall. More bubbles, less release Cold resin and cold molds hold onto bubbles instead of letting them rise and pop, leading to cloudy spots and weak areas in your piece. Many makers warm their resin bottles before mixing, which is a great start. But if you pour that warm epoxy into a cold mold sitting on a cold table in a 55-degree studio, the mold wins. It pulls the heat out of the resin immediately, and you’re right back to cold, thick epoxy full of stubborn bubbles. Why not just crank up the heat? You could turn your studio up to 75–80°F and leave it there all day. That will definitely help, but it comes with downsides: High heating costs, especially if your space is large Uncomfortable working conditions after a few hours Uneven warmth in big or drafty rooms Instead of heating every cubic foot of air in your space, a smarter strategy is to warm the epoxy and the molds themselves. Warm from underneath: simple solutions Targeted, gentle heat under your molds and work surface keeps your resin in the sweet spot without roasting you or your electric bill. Here are practical ways to do it: Seed-starting heat mats (2′ x 4′ style) Great for: multiple small molds or trays Benefits: Provides a broad, evenly heated surface Often includes a thermostat and probe so you can set and maintain a consistent temperature Affordable and widely available online How to use: Place a silicone mat or board on top of the heat mat Arrange your molds on that surface and let them warm up before pouring Use an infrared thermometer to verify you’re in your target range Reptile heating pads Great for: one or a few molds at a time Benefits: Compact and low wattage Some include basic temperature control or can pair with a standalone thermostat How to use: Place the pad under your mold board, not directly under thin silicone alone, to avoid hot spots Check the surface temperature with an IR gun and adjust as needed Tiny low-watt pads for single molds Great for: test pours, small memorial pieces, or one-off molds Benefits: Very low power draw Keeps a single mold in the ideal range for bubble release and curing In each case, the goal is consistent, gentle warmth—not hot spots. Lifting your molds slightly (on a board or cooling rack) and using a mat beneath helps distribute heat more evenly across the entire piece. Scaling up: build a heated epoxy table If you are running a busy studio or production shop, a heated table can be a game changer. Instead of managing multiple small mats, you turn an entire work surface into a controlled, warm “hot box” for your projects. A typical setup looks like this: In-floor heating wire laid out in a grid pattern Sensor probe embedded in the middle of the panel Dedicated thermostat mounted nearby Heating grid sandwiched between two sheets of MDF or similar board This creates a flat, durable work surface that you can set to a specific temperature and hold there. You can: Pre-warm boards, molds, and resin containers before you pour Keep large projects warm and stable while they cure overnight Run several tables from a single thermostat by using longer heating cable (within electrical limits), making it a very efficient system Because these systems are typically in the hundred–hundreds of watts (not thousands), they offer a surprisingly inexpensive way to keep your epoxy projects in the ideal working range without trying to turn your whole building into a sauna. Practical winter workflow Combine these habits for reliable winter results: Warm the resin and the molds before mixing and pouring. Use targeted under-heat (mats or heated tables) instead of blasting the whole room. Monitor temperatures with an infrared thermometer for consistency. Allow extra curing time—cold still slows the reaction, even with good heat management. Manage the temperature where it matters—at the resin and the mold—and winter becomes a season of smooth pours, clear casts, and far fewer surprises. TRANSCRIPT Hi, it’s Tim with iCoat. We’re in the winter months now, so instead of battling exothermic reactions like we often do in the summer, the main issue is epoxy that’s too cold and doesn’t release bubbles very well. We’ve talked extensively about warming the epoxy to a good working temperature, and many of you are already doing that. However, if your studio is 55–60 degrees and you pour warm epoxy into a cold mold, that mold will immediately pull the heat out of the resin. The epoxy cools down right away and can’t release bubbles properly, which leads to cloudy, imperfect casts. There are a few ways to solve this. You could turn the whole studio up to 75–80 degrees, but that’s expensive and uncomfortable to work in for hours. A much better approach is to warm the molds and the work surface from underneath. There are several tools that work well for this: On the medium scale, there are seed-starting heat mats you can buy online. A common size is about 2 feet by 4 feet, and they’re reasonably priced. They can hold a lot of molds and usually come with a thermostat and