The paint film bites the bottom, that is, within a short period of time after the painting is finished, the paint film of the previous coat of paint will automatically expand, shift, shrink, wrinkle, and bulge, and even cause the previous coat of paint to lose its adhesion and appear peeling Phenomenon. The reasons for bottom bite and how to prevent it are as follows:
(1) On the surface of oil-based paints such as general grease paints and alkyd paints, if you encounter paints containing strong solvents, especially when the topcoat is very thick, the bottom paint film is easily swollen and bulged by the solvent in the top paint. rise.
(2) Before a layer of nitro-lacquer (or perchlorethylene paint) is dry, when another layer of the same kind of paint is applied, the bottom will often occur.
(3) If the primer and topcoat are not matched, the bottom will also bite.
In order to avoid biting the bottom and improve the adhesion of the paint film, attention should be paid to the compatibility between the primer and the top coat. It is recommended to use the same performance paint and the same performance thinner for matching coating. When the material is not available, it can also be matched with phenolic paint, ester glue paint, calcium ester paint and oily blended paint, varnish, tung oil, lacquer and thick paint; It can be used on the lower layer of the previous paints, or after the paint film of the previous paints (except lacquer) is effectively dried, then it can be used on the top layer, or it can be used on the upper layer of shellac paint, nitro paint, and perchlorethylene paint. Shellac paint, nitro paint and perchlorethylene paint, in addition to being used alone, can also be used as the lower layer of various slow-drying paints. However, shellac paint cannot be used for the middle layer of slow-drying paint, and other paints cannot be used for the upper layer of large paint. In addition, pay attention to the interval time between two coats of paint and the appropriate solvent. In this way, it is not easy to bite the bottom again.
