(1) the printability surfaces attached to the dirt and oil stains and other substances.
(2) the printing ink itself has bubbles or viscosity uniform.
(3) printing too fast or printing speed is not uniform.
Have a bubble internal factors is: because ink viscosity and surface tension of ink, printing ink of gas oil from ink film to skin to escape and stranded in ink layer. If the ink low viscosity ink surface tension is small, the bubble will disappear on its own, and also won't appear on the phenomenon of printed ink bubble.
Usually use the following measures to prevent ink layer bubble:
(1) use as far as possible hydrophobic solvent.
(2) the ink itself have bubbles, may in the printing ink join the amount defoaming agent. If the ink poor liquidity, when the screen plate up the, the ink flow are small, can't will screen trace fill and level up, get surface smooth level off of the ink layer.
In order to prevent appear after printing screen trace, can use the following methods:
(1) use of fluidity big some ink printing press.
(2) can consider to use the drying speed slow ink printing, increase the ink flow time make ink is progressive curing.
(3) in the plate making use of silk diameter as far as possible when fine single size screen.