It's Nice to Fool Mother Nature

It’s Nice to Fool Mother Nature

Climates can be pretty extreme (too hot, too cold, too dry, too humid), but these days, the right preparation, products and professionalism are a solid defense against weather problems that try to attack a good paint job.

We all know that a quality paint job requires technical prowess. But sometimes the deal breakers in a service operation come after all the hard work and logistics have been handled. The barometer drops off the chart and the dew point arrives, kissing your profit on a paint job good-bye.

But these days, controlling for changing weather conditions isn’t as hard as it used to be. When you combine the technological advances of paint products with the ongoing cumulative learning of paint technicians, it’s evident that weather problems shouldn’t be problems at all – if you do what you’re supposed to do in the paint shop: Follow directions, avoid taking shortcuts and use the right products.

Things Are Heating Up

Shops located in the Sunbelt states – Alabama, Florida, Georgia, Kentucky, Mississippi, North and South Carolina and Tennessee -can experience sustained temperatures higher than 100 degrees F. Inside, the shop can reach the upper 90s unless you employ climate-controlled temperature zones. Under those conditions (and modern spraybooth technology aside), paying attention to mixing instructions and choosing the correct reducer for temperature and other climate-related variables should be first and foremost on the professional paint shop’s list.

Keep in mind the real weather gremlins that plagued the older paint systems – including lacquers – have all but disappeared. In the process of washing out all of the unstable thinner-cut pigments and lowering volatile organic compound (VOC) levels, a lot of the past careful nurturing of the paint process has become unnecessary.

“Attempting to work a two- or three-stage paint system in a similar fashion to an old lacquer or synthetic enamel system is asking for trouble,” says Jim Burns, owner of Jim’s Auto Body in Forsyth, Mo., who regards the radical weather changes in the Southwest Missouri region as “as challenging as you’d ever come across.”

“The trick is simply: preparation, preparation, preparation,” he says. “We’ve become experts [in avoiding problems] because we follow manufacturer instructions on system use, including proper prep, to the


Brian Richardson, a veteran senior line painter for Don Wessel Olds/Honda in Springfield, Mo., has seen the problem areas – blistering, pitting and cratering – that might occur while completing a job during a hot and sultry time period. He says using correct paint components, especially the correct temperature reducer, solves these problems.

Because drying times decrease dramatically when it’s really hot, you must introduce the required internal paint system reducer to compensate for the extreme temperature zone you’re in. In addition, the humidity may require that you add another tacking stage to the final surface wipe-down.

Richardson also points out that dry spray and mottling paint problems can be eliminated through proper air and gun settings and by material fixing – using solvents, retarders or accelerators. The HVLP spray equipment is a real boon in solving a lot of these previously seen problems, and the booth you use can help, too. “We keep our booth at 78 degrees,” says Richardson. “And by virtue of its downdraft design, we can effectively control product application and deter the effects of a sultry day.”

Blistering Cold Days

Chuck Perlick, owner of a body and paint facility in the Minneapolis area, contends that careful use of reducers has made weather-related problems non-applicable. His sidedraft booths are kept at about 70 degrees F, and he has few problems with any temperature or humidity conditions despite being in notably cold Minnesota.

“Product problems crop up from time to time,” says Perlick, “But I just get away from the product, and the problem goes with it.”

He says that some shops may be tempted to use a more economical clear or to make another change within the designated paint system to compete for a job. But don’t do it, Perlick warns. It doesn’t make sense to mess with a system you know works. These cheaper products can require forced drying by baking, an unnecessary process in Perlick’s operation because he uses quality clears that can be buff ready an hour after spraying.

Painter Jeff Martinez of Coradino Auto-Body in Trinidad, Colo., says that even in sub-zero weather conditions, the paint systems work well if booth and surface temperatures are controlled within the shop environment. And experts say that 145-degree drying for 10 to 20 minutes can all but eliminate bothersome flash-off times in between coats, dramatically increasing production. Using retarders or other chemicals can also increase production levels in high-volume shops, eliminate any temperature-related paint concerns with regard to baking and give the shop owner precise control of the completion and delivery time of the vehicle.

When force drying in cold temperature conditions, use heat in short time increments to act as a buffer if you’ve put down too much color. Dry the paint in stages – even under the lamps when possible. Your reducer selection is important here. If you’re working from the positive edge (i.e., using a sub-65 degrees F reducer), you’ll probably be OK. If you haven’t tried to shotgun it and have run the system through a viscometer, your mix may still work out OK. Forced drying can only help. On the other hand, if you’re using only mixing ratios without some kind of intervention, the temperature factor is pretty much left out. It’s a crapshoot here for flash-off and forced drying intervals. Waiting until the following day to apply the clear may be the way to go if you’re in this predicament. Read the label or sheets on dwell times and periods to wait for re-coating.

What about blistering? Martinez says this isn’t a problem with air dry but could be with a high temperature baking system. To get a handle on this problem, I visited Fred Lewchik, lab specialist at BYK Chemie USA, in Wallingford, Conn. He explained that solvent-based coatings produced by BYK are designed to work with silicone additives to adjust surface slip, substrate swelling, overspray acceptance and flow behavior in high build-up systems.

“A lot of OE finishes go down at around 265 to 270 degrees F,” he says, “This is where the product we make is best suited. The factory people use it to keep the topcoat or surface open so the solvents can get out and evaporation can occur as planned by the paint system manufacturer. If this isn’t the case, the finish will suffer from a blistering effect or solvent pop


Don’t Get Rusty With Undercoats

Burns points out that a good vehicle undercoat is the critical factor in beating weather problems. “We just don’t have these problems anymore,” he says. “I can only attribute this to the quality aspect that we’ve built into our prep, painting and handling procedures.” Lay down the undercoat as if weather isn’t a factor. Durability is

built into the paint system, if you follow the instructions.

Most veteran painters say a solid undercoat foundation should be a primary goal on hot or cold days. “We use a solvent-born undercoat formulation that’s polyester-based and works as a guide coat so we can avoid under-glossing of the topcoat,” says Richardson. “Sometimes a separate primer-surfacer is also used to allow for a quicker build and for some sanding if defects show up.”

To maximize protection from oxidation, rust and corrosion for sheet metal car bodies in harsh corrosion areas of the country or when high amounts of road salt are used to clear ice from roads, Tom Hiley, painter for Dobbs Autobody in Salem, Ore., uses an epoxy primer two-stage product before and after applying a primer-surfacer when building the undercoat. Spraying the epoxy primers in such a fashion has just about eliminated harsh wet-weather electrolysis corrosion and other oxidation incidents on repainted vehicles. “Do yourself a grand favor,” he says. “Use the specified hardener, reducer and clear for each application. Weather problems will be pretty few and far between if you subscribe to this philosophy.”

Primers and/or primer-surfacers are the final undercoat product and are designed to be sanded and smoothed. Although some primer-surfacers may resist moisture – so wet sanding can be accomplished – some products can actually absorb water. This makes wet sanding a “no option” situation, and in these cases, the vehicle needs to be wrapped in plastic or parked in a humidity-controlled booth or station prior to topcoating. Otherwise, trapped moisture in the primer is encapsulated in a porous, talc-based material. And after the finish has been sprayed and cured, the water will leech its way down to the base metal and begin a corrosion cell. The best way to avoid this is to identify the correct primer or surfacer sealer that will not only work well during the sanding process, but will also be compatible with the topcoat and the other elements of the paint procedure.

Remember that high-solids color coats are problematic with regard to reducers if you exceed the mil thickness. Staying with one or two mil thickness in the color coat goes a long way toward curing the paint system as a whole. Five or six mils can discourage proper flash off from the last coat or two. Add to this a sudden plunge in temperature and humidity – this often happens in Colorado – and you may find yourself with a problem in the clearcoat or a possible shifting of color and hue. Solve this by putting down just enough color to give the finish its true color and hold-out. Follow paint system guidelines on application, especially where cross-coating is required, and get through the color stage and to the clearcoat as soon as possible.

Flop, Flash and Flow-Out

Metallic “flop” can eat your lunch, say many of the painters I spoke with. Richardson asserts that short dry periods almost always keep the flakes up high, altering the color and/or metallic effect. The key here is to use the correct reducer and to practice on test panels to figure the specified dwell or flash-off times between coats. “The results you arrive at on the test panel will be pretty close to what you’ll see on the vehicle,” says Richardson.

The solvents or reducers necessary on a hot day should have an evaporation index at the low end of the scale. Also look for a low proportion or non-existence of ether alcohols in the formula for high-temperature reducers. This generally points to longer evaporation times and will keep you out of trouble.

At Central Dodge Auto and Paint in Springfield, Mo., test panels are used to gauge color hue and tint and to help develop control over flow-out or metallic flop problems. Dry spray problems fall under their troubleshooting guide for “air system filters and plumbing” because often poor airflow to the gun can makes the pressures go up and down, wreaking havoc when spraying topcoat or clears. Temperature control in spray areas as well as in mixing rooms is recommended. Ranges or variations in baking temperatures are also carefully prescribed. Several experienced painters say that times under the heat lamps or baking temperatures all add up to proven methodology to beat temperature and humidity problems with any paint system. And, as always, staying within the manufacturer’s paint system for all product entries on a given job is recommended.

Picking the Right Products

A lot of the universal catalyst and reducers designed for application are an attempt to provide an economical answer to paint system application when that system has dozens of possible varying requirements. You can shoot yourself in the foot by using such products when the temperature is really hot, cold or humid.

The major paint systems have research that tells them – and hopefully you – which elements of a particular in-system paint grouping can be used in a specific application. Temperature is a critical variable here. Why? Because everything from the reducer makeup to flash-off times are involved. Exiting the parameters of the paint system isn’t only problematic with regard to a color match, but attacks the foundation of the paint system cross-link capability. This can result in a solvent pop problem, a cold-weather wrinkling of the topcoat or other difficulties.

To prevent all this, use the “refinish manuals” supplied by paint manufacturers to obtain the critical values toward selecting the correct reducer. This way you’ll know, for example, that in a certain climate condition a high-solids color should go down at 82 degrees F. And then you can add this kind of information to your shop’s database.

Most modern paint systems should perform without the use of auxiliary chemical additives despite drastic temperature changes. One to two ounces of accelerators added to a gallon of paint will work as indicated on the can if your reducer is also correct for the application. On the flip side, you can bet that if you’re using a mid-temperature reducer with an uncontrolled booth environment on a hot day, the bit of magic you expect from the retarder won’t materialize at the levels displayed on the can. So now what? What if your mix has already affected the flow-out rate, cross-linking attitudes and other important chemical concepts built into the paint system? You certainly can’t go back and attempt to troubleshoot the problems you now have by using the original paint system guidelines. Once the boundaries of the paint formula have been violated, most say there’s little chance of going back.

The Weather Can’t Hurt Me

It seems the newest paint systems are pretty bulletproof against weather-related difficulties. New chemical agents can also help during extreme situations and high production quotas. Drying temperatures, however, shouldn’t be altered from those recommended by paint system and booth manufacturer specifications without prior experience or before consulting a manufacturer’s rep in each case.

But keep in mind that the newest paint systems won’t do you any good if you aren’t using them correctly – which means you need to implement all elements within a manufacturer’s system to achieve desired results.

Use application sheets, instructions on the product labels, color matching and mixing tools, and your single best resource, the manufacturer’s representative, when you feel you don’t understand a product or procedure. By working smart, what Mother Nature is doing outside won’t affect what you’re doing inside your shop.

Solving Solvents
Westside Auto-Body in Marshfield, Mo., is owned and operated by Andy Kirkendohl. Although the shop has a turbine HVLP system in place, the painters sometimes prefer to use the older type of spray equipment. Solvent systems are matched to the temperature conditions, but water droplets that might be induced by air pressure temperature drop (where the air is expanding as it leaves the nozzle while the temperature drops) can be a problem with high-solids and some single-stage systems. Another good reason, in some cases, to stay with a higher pressure paint application system is to lay down difficult metallics more evenly. “The moisture problems that seem to crop up from temperature or humidity never show up with factory booths that are temperature and humidity-controlled,” says Kirkendohl.
Read the Fine Print

Take any product service information sheet from a paint manufacturer and you’ll likely find a disclaimer at the bottom spelling out that the manufacturer can’t anticipate or control every possible condition in which a product might be used. This means that a shop painter and your paint rep should be joined at the hip, so to speak, when a paint or system problem crops up.

Getting the Right Coverage

The only consistent regional complaint that I can report with regard to a possible climate-related difficulty with newer paint systems involves the amount of coverage that takes place with any given product when the climate is at its radical worst.Theoretical coverage – called “mileage” by the pros – is the expected surface area covered by a gallon of product when using the specifications given for the paint. This is often included on the can label itself. Assuming the use of the correct reducer, this doesn’t take into account other variables, including the shape of the part, the porosity and temperature of the application surface, overspray, material left in containers, guns and lines, and booth or paint station temperature. This theoretical guideline, then, is a sort of ballpark inference when the climate is controlled for weather.

A more reliable way to pull things together is by using the “actual coverage” calculation value, which is based upon a modified version of the theoretical coverage formula. To do this, you must first know the transfer efficiency at the temperature and air pressure you’ll be working with. Contact the manufacturer for more on how to determine this with any given product in their line. The resulting calculation will provide an estimate of actual coverage.

How to Minimize Soak and Dulling

Conditions: Low Temperature, High Humidity

1. Raise air pressure 5-10-15 psi. Get the solvent out.

2. Use a faster evaporating reducer (enamel) plus retarder, a fast/slow blend.

3. Apply heat. Remove the solvent from the wet film.

4. Allow two to three times the dry times between coats.

5. Reduce the volume control on the spray gun, increasing pressure vs. material flow to increase solvent release between gun and work.

6. Use minimum recommended reducer amounts, i.e., if range is 50 to 75 percent, use 50 percent (1 to 2) instead of 3 to 4. It’s important to reduce fluid flow when reducing at the lower limit to gain a smooth surface and correct film build per coat.

Conditions: “180” Days (Days when the temperature in Fahrenheit and the relative humidity equal or exceed 180 when added.)

1. Raise air pressure 5 to 10 psi to evaporate more solvent between gun and work.

2. On 180 days, allow twice the recommended dry times between coats to get the solvent out.

3. Use the correct paint solvent for temperature conditions. Don’t use a solvent too slow for conditions.

4. Use the recommended amounts of retarder. Don’t over-retard.

5. Don’t over-reduce final coats to achieve smoothness. Too much paint solvent will be introduced into the paint film. Over-reducing guarantees a hazy finish.

6. The use of a clear harmonizer will help to achieve a smooth surface with resin protecting the metallic.

Information courtesy of Martin Senour.

Writer Bob Leone, a retired shop owner and contributing editor to BodyShop Business, is ASE three-way Master Certified and is a licensed secondary and post-secondary automotive instructor in the vocational school system in Missouri. He is also a former NAPA A.S.E. Technician of the Year.

For more advice on dealing with weather-related paint problems, go to

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