Body work is a skill which requires a great deal of patience. The old fashioned leading process (melting lead in place), has been supplanted with the newer plastic processes. Bondo has become synonymous with body filler material, and is made up of polyester resin and clay. It is cured, or catalyzed with a peroxide, which is generally carried in a solvent such a MEK (methyl ethyl ketone). Often these catalysts will have a color so when mixed with the resin material, a certain hue will be evident and with experience, the worker will know just about how much time he has to work the material. If the mixture is made too hot, (too much catalyst), not only will the working time be limited, but the strength will be compromised. The amount of catalyst required will also very with the ambient temperature, or whether the mixture is being applied in the sun.

It is much better to apply the filler material in thin layers and built up to the contour slowly. The polyester material has the ability to bond to itself through the process called cross-linking. During the hardening process, each molecule reaches out and grabs the adjacent molecule until one giant molecule results. After the filler has begun to set up, it becomes a cheese like substance. It may be worked with a rasp like tool to approximate contour. This must be done carefully so as not to remove filler below the contour. Finally, after enough filler has been applied in thin layers, the surface may be rough sanded with a double-action sander. The process should be repeated with a smoothing putty, which has a finer grade of clay filler, and will sand as smooth as the body needs to be.

After bringing the repair to contour it should be primed with a sanding primer. This is a primer paint that may be sanded smooth and will fill tiny pin holes. Finish sanding should be with at least 220 grit and finally 440 grit sand paper. A technique used by professional body men is to slide the flat of their hand over the repair. Even when you cannot see a slight discontinuity, your hand is sensitive enough to detect it. If you think you may have finished a repair and it looks good to your eye, there will be a time when the sun or light is at a position which will reveal a blemish. Rely on your sense of touch, not your eyes.

When a repair is large enough or there is a gap or a large discontinuity, it will be necessary to reinforce the repair with glass fibers. Glass fibers come in many configurations. You may use mat, which is a felted type material with random oriented fibers approximately two inches long. Roving is a series of continuous glass fibers, similar to a rope, but without a twist. Glass fabric is a woven material with a basket type weave, ie., the fibers are oriented at ninety degrees to each other. And woven roving is a heavy fabric material woven like a basket weave using the glass roving. The strongest material for, say a boat hull, would be the woven roving. It also builds up in thickness faster. This would seldom be used in a body type repair unless there was severe damage.

The most common body material for reinforcement would be fiberglass mat. This is similar to material sprayed with a chopper gun with glass fibers 2 to 3 inches longs in a random pattern mat. It provides adequate reinforcement and is omnidirectional in strength. A useful tool when using mat is a washer roller. This is similar to a paint roller, but is made with a series of washers, approximately 1½-inch in diameter, and ½-inch diameter alternately stacked on a rod. This tool allows the mat fibers to be rolled and pushed down into the resin matrix. For example, if you paint the resin on the repair, and then apply the mat to the wet resin, it is sometimes difficult to wet out all the fibers with a brush. This is true even if you apply a second coat of resin. Use the washer roller over the repair and the resin and mat will be homogenized, but the roller will not pick up the glass fibers. After the repair is reinforced, it should then be finished to contour as described above.

If your bright metal, such as your silver sides or your aluminum is damaged, it will be necessary to replace the damaged part. There are a number of companies across the country which will sell you metal skin panels finished to size. Siding is available so you may cut and size it yourself. It is not my intention to name any firm which furnishes these products. They may readily be determined through various magazines ads.