Important activity before painting

Degreasing the surface is an extremely important procedure in even the smallest paint repair, not only before the painting itself.

The general rule is that the topcoat should be applied over a layer of primer, primer or over the old paintwork. Bare sheet metal must not be varnished, because the varnish will not stick to it well. In order to obtain good adhesion of the varnish, blow out the previously prepared surface with compressed air and degrease it. Surface degreasing consists in spreading small portions of a solvent designed for this purpose with a cloth soaked in it. Then, using a dry and clean cloth, wipe off the solvent before it evaporates. The solvent used to degrease the surface must not react with it. It is only supposed to dissolve greasy deposits on it. Wipe the solvent off the surface with moderate movements, without exerting too much pressure on the surface. In this way, the solvent evaporation process will be slow to obtain the best possible degreasing result. If you do not wipe off the solvent but just let it dry completely, greasy deposits will not be removed from the surface in this way. 

The surface must be degreased not only before painting but also before sanding. First, when sanding a non-degreased surface, lumps are formed from grease and sanding dust. They are the cause of the distinct sanding marks. At the same time, the abrasive wears out faster. Second, the grease particles are forced into the sanded surface by the abrasive grains, where they are difficult to remove afterwards.

In other words, washing the surface with a degreasing agent facilitates and speeds up sanding.