Automotive priming and surfacing

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With the metal in as good condition as it is possible to get it, the next step is to spray on the priming coat. This coat gets a " toe hold" on the metal and helps the following coats to be permanent by furnishing a surface to which they will adhere. That is the only job the priming coat has to do. But even a special primer cannot "hold on" if the metal is not thoroughly clean.

In general there are two kinds of primers—oil base and lacquer base. Neither primer will prove permanent on a surface that is not well cleaned up. However, of the two kinds of primers, the one with the oil base has the ability to absorb a slight amount of oil film from the surface of the metal. This is due to its slower drying characteristic. The lacquer base primer dries so fast that it has practically no time to absorb any oil film that might be on the metal.

However, even if an oil base primer is used do not expect it to prove permanent unless the surfaces are cleaned up to the very best of your ability. More refinishing jobs are ruined by the workman being too anxious to start spraying than from any other cause. Good refinishing is more dependent upon careful work in the preparation of the surfaces than upon great skill in spraying, though the latter is important, of course.

Many consider it best to use an oil-base primer, for while it delays the work a few hours by its slower drying, it does much to assure a permanently satisfactory finish. This oil base prime coat should be sprayed with the material as it comes from the can. However, if it is too thick to handle well, it may be thinned with turpentine.

It is well at this time to mention that the final result depends as much on the quality and suitability of the materials used as upon any other factor. Furthermore, there is so little difference in price between the best grades of the various kinds of material and the cheapest that it is folly to risk the quality of the job for a few cents' saving in material.

And in buying materials it is well to use the products of but one manufacturer—at least on any one job. The products of different manufacturers may be of equally high grade, but by using one brand from prime coat to rubbing compound you know that you have materials that were produced to work together, and if they fail, there can be no "buck passing." In the use of thinner particularly, it is important to use the same brand as the lacquer you are using.

Above all, follow the recommendations of the manufacturer. He knows from experience and research just how each product should be handled. And only by seeing that you use his product successfully can he hope for your continued business. For that reason you may be sure that his recommendations are sincere and should be followed to the letter.

Smoothing the surface

File marks and other imperfections in the surface of the metal must be filled in with putty or they will appear in the finished job. Glazing putty for filling such defects is on the market in handy tubes, as well as in pound and larger size containers.

Some shops make a practice of spraying the entire job with a coat of surfacer and then going over all surfaces with a flexible putty knife and glazing putty to fill the deeper imperfections.

Other shops do the spot puttying first, and then spray on the surfacer. It makes little difference which method is used. They are both good. The difference in results in various jobs would come only from a difference in thoroughness with which the work was done, not from any difference in methods.

If the whole job is first sprayed, then puttied, it should be given another spraying or two of surfacer after the putty has dried and has been sanded smooth.

To save time, some establishments try to finish the hand putty work near closing time. The reason for this is that the putty takes about 8 hours to dry; so, by following this plan, the car is ready to work on the next morning. The final undercoat is another spraying of surfacer.

Surfacers—like primers—are available in either oil type base or pyroxylin base. The oil type base offers greatest flexibility and is especially suitable for use over wood. This surfacer is also excellent for use on metal but requires longer time in which to dry than does the pyroxylin base surfacer.

Oil base surfacers take about 6 hours to dry, so it is possible to put on two of these coats in a day—letting the last coat dry over night.

Another coat in the morning will finish the job of surfacing, except for the sanding. And there is the job. When this last coat of surfacer is thoroughly dry, the car must be wet sanded with No. 220 waterproof paper to avoid scratching. To finish up, No. 280 waterproof paper should be used.

Then if any scratches or other defects appear in the surface, they should be spot puttied. When dry they should be wet sanded with No. 280 waterproof paper.

The next step is to sponge down the whole car with clear water to carry away any slop and dirt from the sanding operation. Watch the corners and cracks. Remember that any dirt dropping out later—or moisture remaining in such places—will ruin an otherwise good refinishing job. With compressed air, blow out all cracks and corners. And with chamois, go over every surface that can be reached.

Then let the car stand over night and it will be ready for the first coats of lacquer in the morning.