What is the reason for the degree of paint that is not used up after opening the barrel, and how to deal with it?

Paint skinning occurs mainly in oil-based or resinous paints containing tung oil. Generally, the knot degree is caused by air leakage of the container, too much cobalt driers, or too high storage room temperature. If the crust is thin, it is easily broken into small thin skin particles and mixed into the paint, which will make the surface of the painted film rough and affect the quality. A thick crust will not only affect the appearance of the paint film, but also reduce the utilization rate of the paint. In the past, painters often cut kraft paper into circles, dipped it in water, and pasted the paint tightly to avoid air contact with the paint to prevent skinning. For the whole bucket of paint, when the dosage is small each time, after pouring out a certain amount each time, immediately add a little "covering oil" (that is, a slower volatile solvent, such as turpentine, etc.) The surface is isolated from the air and sealed with a cover.