Using glue and epoxy in a cold shop

Should you proceed with a cold-weather glue-up? It depends. While each glue has very specific properties, there are a few general principles to consider before you spread the glue. Temperature affects the open working time of the glue. Temperature affects the curing and clamping time of the glue. Storage temperature affects the shelf life of the glue. Temperature (and sometimes moisture) may affect the viscosity of the glue. And finally, not all glues can survive what’s known as a freeze-thaw cycle.

On a recent snow day, I stayed home and spent the day on the phone with glue manufacturers. While it’s impossible to provide you with every permutation of every glue at every temperature, here are some helpful numbers and tips, provided directly by the manufacturers of these products.

Let’s start with the most commonly found glue in the shop – PVA glue. According to technical support at Titebond, the glue will flow above 32°F, but that doesn’t mean it’s OK to use. If you apply the glue at a temperature below the chalkpoint, or lowest viable temperature, the glue will dry white and chalky and lack strength. As for storing Titebond PVA glues, they will survive the freeze-thaw cycle just fine, but if your glue resembles cottage cheese, it needs to be stirred to achieve a normal consistency. While Titebond PVA glue is tested to survive 5+ freeze-thaw cycles, a Titebond technician suggested that temperature fluctuations in storage can reduce its shelf life. While it’s not at all necessary, you might keep PVA glues in the refrigerator year-round to avoid extreme temperature fluctuations. Just pull the glue out of the refrigerator 20 minutes before you plan to use it and ensure it warms above the chalkpoint.

Next up, let’s consider hide glues. A conversation with Patrick, creator of Old Brown Glue, gave me the most hope for life in a cold, cold woodshop. He pointed out that much antique furniture was made in cold New England woodshops, where makers often utilized hide glue. Since hide glue sets with the loss of temperature and moisture, you can do two things to give yourself enough working time for a successful glue-up. First, heat the bottle of hide glue in a warm-water bath, utilizing a small slow cooker, baby bottle warmer, or hot plate. A ten-dollar meat thermometer will help you get the water temperature set somewhere between 130ºF and 150ºF. The second thing you can do is dampen a cotton cloth in hot water and apply it to the wood right before you add the glue. A thin film of moisture will enter the pores of the wood, heat the wood, and help create a stronger bond.

Hide glue can be heated an infinite number of times so long as it’s not heated beyond 160ºF. Old Brown Glue endured a 7x test of the freeze-thaw cycle. But hide glue doesn’t last forever; when the urea breaks down, it begins to smell of ammonia and should be replaced. It’s also worth mentioning that liquid hide glue will flow at colder temperatures and does not generally need to be heated. But once it drops beneath the gel point, say around 40ºF, even liquid hide glue will not come out of the bottle unless heated. Liquid hide glues lack the initial tack of regular hide glue and are unsuitable for a rub joint.

When polyurethane glues are used as an adhesive, say in a wood joint, they can be used at a relatively low temperature. Original Gorilla Glue is also tested to survive 3–5+ freeze-thaw cycles, making it a cold woodshop favorite. But epoxies, which are very rigid, are much more difficult to use in the cold. A low application temperature will have a dramatic effect on the amount of time it takes the glue to cure. Take an epoxy adhesive like West System’s G-Flex, for example. According to a West System’s technician, this product will give you a workable cure at 7–10 hours at room temperature. But for every 16ºF below room temperature, your cure time will double. Every 16ºF above room temperature will halve your cure time. It’s not a bad idea to mix up a test batch the day before a scheduled glue-up to ensure proper cure.

While epoxy can be used as an adhesive in lower temperatures, it is not stable through a freeze-thaw cycle and should not be stored in a cold woodshop or garage. When epoxy is left in freezing temperatures, it will form crystals, which must be eliminated before proper use. Crystallized epoxy can be rehabilitated in a hot water bath for 60–90 minutes. You can use your washtub or bathtub, and change the water every 30 minutes. If you’re using epoxy resin for a tabletop pour, bear in mind that these products often lose their ability to self-level when used below room temperature and will often bubble or crack.

Since woodworkers occasionally have use for super glue, it’s worth noting that CA glues are not particularly effective in the cold. According to a Gorilla Glue technician, CA glue will survive freezing temperatures, but it needs to be thawed to room temperature before use.

The urea-resin glue known as Unibond 800 is a favorite for veneering and bent lamination. It used to be made with 4% formaldehyde, but the current formula now contains 0.4% formaldehyde. This is one of the most sensitive glues to temperature. Unibond 800 should never be applied when the shop temperature or work is below 70ºF. According to a Vacu Press technician, “If you casually think to yourself, ‘My shop is probably 70ºF,’ that’s not good enough.” Whenever possible, throw an electric blanket over your Unibond 800 glue-up for proper cure. On the bright side, Unibond is freeze-thaw stable, but it should be stored in the refrigerator for best shelf life, which is already fairly short.

At the end of the day, if you have questions about your glues and a cold woodshop, place a quick call to the manufacturer. I had delightful conversations with technicians at all of the above companies, and I wasn’t put on hold a single time. Technicians knew their numbers and often had tips or tricks to spare. One Titebond technician even explained to me that if I’ve ever gotten a napkin stuck to my fingers while eating fried chicken, it’s because I’ve actually made hide glue. Should you proceed with that glue-up? You tell me.