Paint models with latex

Model Airplane News, Nov 2003 by Vaillancourt, Roy

Q WHAT'S THE BEST CLEARCOAT METHOD?

A Clear epoxy and polyurethane work well, but again, you must wait until the latex has fully cured. Also, be careful not to flood the surface with the clearcoat. If you plan to use water-slide or vinyl, pressure-sensitive decals, let the latex fully cure before you apply the decals. When everything is fully cured (after about a month or so), you can add a top coat. The key is to apply light coats; don't get the latex too wet. You'll need only a little more than a misting of clear.

Keep in mind that some epoxy and polyurethane paints use a toluene-based thinner that attacks latex. Check the can! Water-based polyurethane and epoxy work fine.

I have top-coated latex many times and prefer to use K&B's clear Hobby Poxy. On my military planes, I mix the clear with "satin" hardener, and I sometimes add talcum powder to the mix. Some modelers don't like to clearcoat because it can "yellow" over time, but my old WW II birds get better-looking with this "aging" process. On sport models, I use a glossy clearcoat and a few coats of auto wax from time to time to prevent UV rays from turning the clearcoat yellow.

I have never used a polyurethane color coat. I don't like to work with these paints because they are too heavy and messy. They are also very difficult to match if you need to repair your plane. If you want to try clear polyurethane, I suggest that you test a few samples first. Spray a piece of glass and let the polyurethane cure for about a week. Then apply raw fuel, and note the results.

Q HOW DO YOU MASK COLORS AND PREVENT BLEED-OVER?

Go to your local auto-body-supply shop and buy masking s tape. Use the good 3M stuff; the blue, low-tack type works best. Don't use cheap stationary-store masking tape. After you've covered all of the areas that you don't want to paint, spray the paint lightly along the taped edge, and gently dry it with a heat gun. Repeat this twice (three times total) before doing the entire area.

After you've applied the last coat, partially force-dry the paint near the tape, and then remove the tape and allow the paint to cure fully.

Q WHICH THINNERS AND/OR ADDITIVES WORK BEST?

A Naturally, most people expect me to say "water." Some guys suggest regular tap water; others use distilled water. Both work well, but I prefer to thin latex with an alcohol/water mix or-better yet!-windshield-washer fluid. Yep; windshield-washer fluid. You can use any brand, including the cheap blue stuff. Don't worry about the blue tint; it doesn't change the paint's color. The interesting thing about them is their soap content; they all have soap, and it slows drying to allow the paint to "flow" more and produce a better finish on almost any part. Once it has fully cured, latex thinned with windshield-washer fluid can be weathered just like epoxy and lacquer-really neat!

The only material I add to latex is Floetrol; it allows the latex to flow out without running. It also lubricates spray guns, and slightly reduces latex's sheen. (Latex dealers will tell you it doesn't, but it does.) You can get Floetrol from stores that supply professional house painters who use it when they roll and spray paint. Add about 2 ounces of Floetrol to a quart of paint before you do anything else. This is the only time you'll add this stuff, so you won't need to buy much.