While printing, Why the pad print silica gel printing often arise the sand hole phenomenon ?

1. The sharp of the pad may wrong, too flat or the angle is wrong.
2. The pad culminating point print in the design, formed air can not discharge, formed air bubble.
3. The pad is stickiness, broken or oil stain.
4. The print plate trapped too deep,  because of the thick oil effect make the pad stickiness incompletion.
5. The print plate is too shallow, and the oily layer can not thick enough.
6. The oil is too dilution or dry so slowly.
7. The oil is too dry or dry so quickly.
8. The sword scratched some oil.