When applying light paint on the dark primer, what is the reason why the dark color will penetrate and how to prevent it?

Paint film bleeding means that after the topcoat is applied, the primer is dissolved by the topcoat, and the color of the primer penetrates into the topcoat, causing the topcoat to change color and affect the appearance. Causes of bleeding are as follows:

(1) The bottom layer uses a material that dries extremely slowly. For example, after scraping the surface with lacquer putty, no matter how to brush water color, oil color or wine color on this surface, even if the color is very uniform just after brushing, after about half an hour, the color of the black spot putty part of the lacquer will disappear. It will all be exposed on the paint surface. Another example is that if the asphalt-coated surface is painted again, traces of asphalt will appear on the paint surface.

(2) Apply the topcoat before the primer is effectively dry. For example, when painting blue or green alkyd enamel paint or blended paint on the wet red phenolic antirust paint, it is easy to make the color of the primer penetrate into the surface of the topcoat; If the paint contains a strong solvent, it is easy to dissolve part of the oily paint, thus causing the top coat to bleed.

(3) Before painting the primer, the oil stains, turpentine, red mercury, dyes, etc. on the surface of the object are not removed, and the shellac paint is not used to seal, that is, the paint is painted, causing the paint film to bleed.

(4) The primer is dark, or contains staining, and the top coat is light. If the white topcoat is painted on the red or brown primer, the topcoat will bleed red or brown, especially the bleeding phenomenon of nitro paint is more serious.

Prevention method:

(1) The bottom layer does not need to be primed with lacquer putty which is extremely slow to dry;

(2) Wait for the primer to dry before painting the topcoat;

(3) Before painting the primer, it is necessary to effectively remove oil stains, turpentine, asphalt, red mercury, dyes, etc.;

(4) Bleeding on the wood surface can be closed with shellac varnish;

(5) When painting different colors of nitro paint, the amount of thinner should be appropriately reduced in the top coat, and the coating should be thin so that the paint film can dry quickly;

(6) For bleeding on the metal surface, scrape off the bleeding part, or seal it with shellac paint or aluminum powder paint;

(7) Use a solvent with a fast volatilization speed and a small dissolving ability for the underlying paint film.