Faster drying strategies

It’s Thursday afternoon and the new kitchen is scheduled to be delivered tomorrow as promised. All that’s left now is to apply a final coat before letting it dry overnight. Only, it’s been raining all day and the air in the shop is saturated and a bit chilly. You’re beginning to worry about being able to load up in the morning…

Sound familiar?

With both oil-based and waterborne coatings, dry and cure times can be incredibly fast or painstakingly slow. So many factors are influential, including the above-mentioned humidity levels in the booth or the shop, the ambient temperature, air movement, the nature of the carriers, and the thickness of the coat. Humidity above 70 percent slows evaporation for water-based products, while temperatures below about 60 degrees Fahrenheit put the brakes on curing for oils and varnishes.

The options for faster and better drying for both oil and water-based finishes include lowering ambient humidity, increasing temperature, and using technologies such as UV. There are also several innovative solutions that let a shop move, handle, stack and dry items such as doors, drawers, shelves, and cabinet boxes. These systems can speed up throughput, save floor space, and reduce rework.

The traditional way to do this is to crank up the air conditioning, and that can be expensive.

It’s a good idea to start with inexpensive monitors that measure humidity in three areas: inside the spray booth, areas of the shop that will be used for drying, and outside. If the air in the shop is more humid than the air outside, opening doors and windows is probably a good option. The biggest concern there is airborne contamination such as pollen and seeds, so screened windows work better than loading dock doors.

Humidity is measured in two ways. Absolute or specific humidity is simply the actual amount of water in the air. Relative humidity measures absolute humidity as a percentage of the maximum amount of moisture that the air could hold at a given temperature. So, if the temperature goes up or down, the relative humidity changes. People (and coatings) are most comfortable when relative humidity is about 50 percent. If a woodworker is going to spray early in the morning when the air is a little chilly, the absolute humidity will be low, but the relative humidity will be high. That’s just because cold air can’t hold much water. As the day warms up, absolute humidity may not change but relative humidity will.

If opening windows isn’t an option or doesn’t do the job, commercial dehumidifiers are definitely worth a look. Most models are less expensive, and often a lot less expensive, to operate than air conditioners. That’s because their main function is just removing moisture and not cooling the air. They come in both stationary and mobile units, and are often used around indoor pools, gymnasiums, and water damage projects. They use cold coil refrigerants or desiccant chemical absorption to remove high volumes of moisture from indoor air — usually somewhere between about 10 and 35 gallons a day. Some brand names for research include AlorAir, Moiswell, Danthern, Waykar and Desert Aire.

If a dehumidifier is going to be used, doors and windows will need to be closed and noticeable gaps should be sealed. It’s also a good idea to add a coat or two of epoxy to any concrete floors and walls, because those surfaces are basically storage units for moisture.

Drying and curing times are very sensitive to temperature, especially for waterborne coatings. As the temperature in the booth or drying area goes up, relative humidity goes down and solvent evaporation becomes faster. Again, relative humidity measures how much water the air could carry. As the air heats up, it expands, and the percentage of moisture gets lower. But the expanded air then draws in more moisture (from the coating) in an effort to find equilibrium, and the cycle repeats.

Booth temperatures around 72 degrees F are ideal for applying and curing most coatings but check the coating product label. If possible, items to be coated should be allowed to acclimate at this temperature overnight before being sprayed.

Localized methods of increasing temperature include mechanical solutions such as heat guns, heat lamps, tunnels, and ovens. These devices heat up targeted areas of the work or the room. The ideal range is somewhere between 140 and 180 degrees F, depending on several factors. The high end here is important: too much heat, or heat too quickly applied, can cause orange peel, separation between layers, and even blistering with some coatings. Again, read the manual. And higher temperatures don’t just speed up evaporation of carriers, they also accelerate chemical reactions and even thin down coats to deliver better viscosity and leveling.

This eco-friendly technology is a favorite among shops with CNCs because it lets the finishing process keep pace with higher production rates in the rest of the woodshop. UV curing acts almost instantly to render doors and other elements handleable. An operator can spray the parts and then pick them up and even stack them within seconds. That means the shop can sand between coats with virtually no waiting and move one job out of the way to make room for the next in short order. So, UV saves on both space and time.

On top of the speed, UV coatings are very durable. That’s a real boon when a shop is applying color to MDF. The finish resists scratches and chemicals, and because the process involves very few or even zero volatile organic compounds (VOCs), environmentally conscious clients welcome it.

The way that UV works is that the booth operator applies coatings by roller, spray, brush or curtain that contain chemicals called photo-initiators. When these are exposed to UV rays, they cause the finish to rapidly polymerize, which is basically changing from liquid to solid. What’s going on is that small molecules join together to create large chains. It’s how plastic is formed. UV curing is called a photochemical process because it combines chemicals and a variation of light.

There are other advantages to UV beyond fast curing. For example, Miltec UV in Stevensville, Maryland (miltec.com) notes that doors can be “UV-cured to protect them from long-term exposure to UV light, preventing the finish from fading over time, and also to act as a moisture barrier for exterior doors.” The company says that its UV curing system offers lower energy usage and operating costs and has the ability to control gloss, improve durability, and increase line speed.

Drying/curing doesn’t have to depend completely on high-tech solutions. For smaller shops, just organizing the way that product moves through the booth and deciding where it sits during air drying can have a profound effect. A system that lets the operator work in a more organized fashion, with a minimal amount of hands-on contact, delivers less rework and faster results.

After the final coat is applied, waterborne finishes will need to flash off for about ten minutes, depending on how heavy the film is. After this dwell period, parts are traditionally moved to drying racks. That involves gingerly picking up each door and trying to handle it by only touching cured or unsprayed areas. But it’s a much better option to be able to spray the parts and let them dry without ever having to touch them.

The PivotPoint from Guffey Systems (guffeysystems.com) is described as a Cabinet Spray Finish and Dry System Kit. Each of those kits is a selection of components designed to outfit small shops that are spraying and drying low volumes of parts. PivotPoint is a big upgrade from flat finishing, and the various kits can transition into the company’s larger PivotLine finishing system as production increases. Each kit contains various elements such as mobile drying racks with special hangers for doors and drawers. It’s very customizable, and the company will help a shop design or purchase what it needs for specific volumes and budgets.

California-based PaintLine (paintline.com) also offers both spraying and drying solutions, with an emphasis on jobsite portability. The company even makes a Portable Jobsite Spray Booth that sets up in minutes. And for woodshops looking for ways to manage drying, the ProDryingRack system is a complete range of mobile and stationary drying racks that are specifically designed for woodworking and cabinet shops. Among them is the adjustable PRDAD, which can be set up with options that can accommodate high volumes of product   such as 80 cabinet doors or 160 drawer fronts. Taking up very little floor space, it has adjustable depth shelving that can also accommodate larger items like cabinet face frames and panels. The PRDAD, which has 5" casters, is one of several mobile options from PaintLine.

Total Finishing Supplies (totalfinishingsupplies.com) also offers a wide range of mobile or stationary drying racks under the Raider, Pro and Hulkrack2 brand names.

Green-Fast-Cure (greenfastcure.com) is a Washington, Indiana manufacturer of infrared delivery systems that cure coatings. The company’s technology works by mixing fresh air and gas for a more effective infrared cure, which results in time and energy savings for woodshops. The plug-and-play technology means it can be installed just about anywhere and be up and running the same day. It’s a safe solution that can cure parts in as little as two minutes.

Carlisle/Binks (binks.com) designs and manufactures electric infrared curing systems, including ovens, boosters, and portable arms for powder, liquid, UV, and adhesive coatings. This technology applies radiant energy to the surface of a door or shelf, heating only what needs to be heated. Unlike home heating systems, it doesn’t warm up the surrounding air. This direct transmission takes less time and energy to cure coatings. The system can work with oddly shaped objects, demanding substrates and difficult coatings including powder. Depending upon the cure time desired, Binks offers short wave infrared curing with T3 tungsten filaments, medium wave with a nickel chromium coil tubular element, or ceramic long wave capabilities. And solutions are offered in a variety of emitter wattages, heater sizes and voltages to suit most shops’ needs.

Several other portable curing systems including brands such as DeVilbiss, BGK and Cerakure are available online from Total Finishing Supplies.

Coating, drying and curing all use up a shop’s expensive heated or cooled air, but Toronto-based Ventless Inc. (ventless.com) has a solution for that. The company offers spray booths that use a patented, multi-stage filtration system that means they can operate without any external venting, ductwork, or air make-up units. They recirculate up to 90 percent of the air they use by sending it back into the workspace after removing any volatile organic compounds (VOCs) or other contaminants, according to the company. Ventless spray booths have a standard main filter designed to trap particulate, and an additional set of activated carbon filters that act as a holding ground for fumes and VOCs.

SCM Group (scmgroup.com) offers a range of products designed to deliver faster and better drying solutions in the woodshop. The company’s Superfici brand includes complete automatic or robotized spraying lines, flat dryers, vertical dryers, UV and UV led curing systems, and complete roller coating and curtain coating lines, along with printing machines, robots and 3D lines for doors, window frames and three-dimensional panels.

Faster and better drying options really depend on scale. The more parts the shop finishes, the more options there are. But almost every system can benefit from that first, basic rule: a woodshop needs to be able to adjust humidity and temperature if it wants to control the speed and quality of parts drying and curing.

Originally published in the June 2026 issue of Woodshop News