Affected by foreign matter (such as oil, water, etc.) existing on the surface of the coated object (or mixed into the coating), the coating cannot be evenly adhered, and the phenomenon of shrinking and exposing the coated surface occurs. Because the causes and phenomena are quite different, those with a large and irregular exposed bottom area are called shrinkage (commonly known as laughing); those with a circular shape are called shrinkage holes; those with particles in the round holes are called "fish eyes" . This defect occurs on the wet paint film just after painting, and sometimes it is only found in the dry paint film after drying.

Reason:

(1) The surface tension of the coating used is high, the leveling property is poor, the release of bubbles is poor, and the sensitivity to shrinkage is high.

(2) The paint mixing tools and equipment are not clean, so that harmful foreign matter (some invisible to the naked eye) is mixed into the paint.

(3) The surface of the coated object is not clean, and there are foreign objects such as water, oil, dust, soap, silicone, and grinding ash attached.

(4) The air in the coating environment is not clean, with dust, paint mist, silicone, wax mist, etc.

(5) Coating tools, work clothes and gloves are not clean.

Prevention:

(1) When developing and selecting coatings, pay attention to the sensitivity of coatings to shrinkage.

(2) In the painting workshop, there must be no substances harmful to the paint, especially silicone.

(3) It should be ensured that the compressed air is clean, free of oil and water.

(4) Ensure that the coating environment is clean, and there should be no dust, oil mist and paint mist floating in the air.

(5) It is strictly forbidden to touch the coated surface with bare hands, dirty gloves and dirty cloth to ensure that the coated surface is clean.

(6) When spraying paint on the old coating, it should be sanded thoroughly with sandpaper and wiped clean.