Pinholes

Pinholes are small very narrow channels-holes perpendicular into the paint surface.  These circular defects on the paint surface typically range in diameter from about 0.1 mm to 1 mm. The defect may range in appearance from a very narrow hole just into the clearcoat or a deep hole which extends all the way to a lower paint layer. They can often be observed in the wet paint but are most troublesome as defects in the baked paint.  Pinholes can be observed in all layers-clearcoat, basecoat, or primer.  

Also known as: pinholing, pin pricks, “pops”

Pinholes are normally caused by a defect in a lower layer.  The next layer in the film cannot cover the defect and a surface tension gradient that causes the paint to flow away from the hole, resulting in the pin hole defect.  

Since the pinholes are often formed in a layer above which a pop or other defect occurred, it is best to avoid any pop in lower layers. 

See Pop -> Tips to Avoid