The Preval Spray system is a terrific and economical tool for spraying many varieties of paints and on different surfaces.  Preval sprays lacquer incredibly well, as well as many types of enamel and waterborne paints.

The very first step in spraying is to get to know your Preval Sprayer.  Get to know what you do best with the Preval Sprayer as well as what you don’t do well. This is best achieved by trying out your Preval on an old piece of scrap wood, or any old piece of sheet iron.

Treat the Preval spray system as you would a precision tool. Make sure to keep the reservoir and spray nozzle clean – you will get many uses from your Preval unit this way.

*Note: When you finish spraying, or are changing color, put some thinner in a cup and dip the nozzle in the thinner. Spray this thinner in a safe area until you don’t have any more color coming out the nozzle.  This will clean your entire system.

Lacquer and enamel

There are important differences between handling lacquer and handling enamel. Lacquer is more fluid and more volatile than (synthetic) enamel.

Due to the volatility of lacquer, use your Preval to spray closer to the surface—a distance of 6 or 8 inches is best. (Synthetic) enamel works well-sprayed 8 to 12 inches from the surface. Working too close with either finish is likely to cause a wet, heavy area that may sag.  There is a greater chance of this happening when working with synthetic enamel.

The drying is very rapid with lacquer, so holding the Preval spray system too far back will cause the material to dry in the air, resulting in a rough surface. This is not as much of a concern with enamel.

The action of either product is influenced by the manner of thinning, the lacquers usually (per paint manufacturers direction) being thinned with 1 1/2 to 2 units of thinner for each unit of lacquer. With synthetic enamels there is generally (per paint manufacturers durection) 1 unit of thinner to 5 units of enamel. It is interesting to note that since there is more solid material in the enamel, one enamel coat is equivalent to several coats of lacquer.

Most often, a lacquer finish consists of 3 or 4 double coats. A double coat is generally considered to be the result of covering the surface first with overlapping horizontal strokes and then with a series of overlapping vertical strokes. Studying the spray pattern will determine how much to overlap. Think of the spray pattern as being in three sections:  When sprayed correctly, the middle one-third will cause the outer thirds to thin. If the strokes are overlapped by this amount, the entire coat will be of uniform thickness.

When handling polychromatic finishes, lacquers should be applied with one fairly heavy wet coat followed up by two or three mist coats. This is just the opposite of applying the straight lacquer finishes, which should be put on with a thin coat first followed by wetter coats.

In handling the polychromatic synthetic enamels, there should first be a heavy coat sprayed on—being very careful not to get it so heavy as to cause it to sag, and then this should be followed by a thin coat.

The manner in which these two finishes dry differs widely. Lacquers dry by evaporation, and can be polished under normal conditions in about 1 hour. Synthetic enamels have a preliminary drying by evaporation and then harden through oxidation of the oil. No polishing should be attempted for 48 hours unless the job has been oven dried. And even then, sanding or polishing tends to remove and ruin the sealing effect of the synthetic enamel and thereby reduce its durability.

Before you get to thinning your lacquer, make sure to experiment to get the best viscosity. There is a difference in thinners and only by experience can you know the exact quantity to use. This is especially true when spraying heavy material to obtain a glossy surface.

When you use higher quality thinners, which is rich in slow-drying solvent, you are more likely to get your desired effect.

The quality of the thinner you are using makes a difference in the quantity needed for any specific application. Test your samples. Watching the proportion, prepare a small quantity of material and try it on some old part. If it is difficult to apply, gives an uneven effect, add more thinner. If it fails to cover the surface or tends to be iridescent—has "rainbow colors "—too much thinner has been used.

When the proper proportions are found, make note of them and use the same proportion for each mix.

Get to know the "feel" of your Preval spray system. Holding it near a practice surface, gently squeeze the trigger as you sweep your arm across the panel. For flat surfaces the Preval should be adjusted to give a "fan" shaped spray. A. well-adjusted spray will have quite uniform distribution of material. However, the outer ends of the fan will have less material than the centre. If the fan is covering a 6-inch width, the outer 2 inches of each end will be fairly light.

The center 2 inches will be quite "wet." In working the Preval spray system, keep all strokes parallel and overlap each stroke so that the material is of uniform thickness. Stop the flow of material at the end of each stroke or runs will result. You will get better with experience.

Three to five coats if using lacquer should be sprayed onto the body, hood, and fenders, too, if they are to be the same color. If a different color is to be used on certain parts, masking will be required.

The first coat should be very light. If too much material is sprayed on, it will tend to raise the oil undercoats. For that reason, have your material quite thin, and spray on but a mist the first time.

About 30 to 60 minutes should elapse between coats. However, if you are working alone on the car, your spraying can be practically without interruption. By starting, let us say, at the right front fender and working all the way around the car, it will take 30 to 60 minutes. Then you'll be ready to start the next coat at the right front fender.

Before going ahead with this, however, it is best to give the chassis, running gear, and under side of fenders two coats of chassis gloss black. The reason for doing this now is to guard against the harm that would result from the black blowing onto the finish of the upper part of the car. Of course, the spraying of the under part of the job may be done at any convenient time after having been washed and wiped off with gasoline. Also, if the engine is to be refinished, it can be given a coat of grey engine enamel when the chassis is being taken care of.

In spraying the upper part of the car, hold the Preval spray system at a uniform distance of 6 to 8 inches from the surface for lacquer and 8 to 12 inches for enamel. Do not use your arm as a radius, thus drawing the Preval away from the work at the end of each stroke. Be sure the Preval unit follows the curve of the body—not the arc of your arm. See left.

Left are two identical panels are represented. In the upper, the gun is held at the right distance and the material started as the gun approaches the panel and stopped as the end of the panel is passed. The result is as it should be.

In the lower, the Preval unit is swung with the operator's arm as a radius. Even though the material is started and stopped at the right time, the sections indicated by B and C will be rough, and A will probably have runs in it.

Holding the Preval unit even a little too far away creates excessive finish dust and causes a rough surface. Holding the Preval unit closer lets the finish strike the surface while too wet, which tends to cause runs. Other things that cause runs are the use of too much thinner in the material or holding the gun in one spot.

*Note: runs are extremely hard to work out.

Lacquer, unlike enamel, softens the under coats and becomes a part of them. That is a great advantage in the final finish, but a great disadvantage when runs occur, for it means that attempting to wipe the runs out may take off the finish down to the metal.

The only way to take out a. run is to let it dry thoroughly and then sand the spot smooth. This is done, of course, before the final coat is applied.
But until you are thoroughly experienced in mixing lacquer and enamel and in handling the Preval spray system, practice on junk pieces whenever you can. Some operators keep an old fender handy to use as a "target" to try out new mixtures—or different gun adjustments. It might be worth your while to do the same thing and thus avoid the chance of creating runs or sags in the finish of your work.

Masking for two-tone work

Any painter's supply store can furnish masking compound, masking tape, and paper. Newspapers can be used, but there is the danger of its printing on the surface of the car if much lacquer is sprayed against the outer side. The thinner has been known to soften the ink on the newspaper, thus making it print. Brown paper is not very expensive and is much more convenient than newspaper, being larger and stronger.

Masking compound is used on windows before doing any spraying. This compound can also be used to protect metal parts that are not to be sprayed. And some operators use it to protect the body itself in two-tone work. However, to get sharp edges it is necessary to finish off with tape.

After the parts that are not to be sprayed are covered, the surfaces that are to receive the other color should be given two or three coats, assuming a lacquer job.

Then let the whole car stand for at least one hour, and then remove tape and paper. The masking compound will wash off with clear cold water. Use nothing but water—but use plenty of it. At this time the compound should be removed only from the lacquered surfaces of the body if this method of masking was used. Leave the compound on the windows and metal parts, for a final "flow" coat of lacquer thinner is yet to be applied. 

You will be delighted with the professional look of your finish using the Preval spray with these finishes.

- Emanuel G