hello there,

I' m new in screenprinting and i am trying to screen print on rack surfaces which i' ve prepaint with graffiti spray color. The material of the color which i acquired from the local dealer after his advice is vinyl. But while i have a good printed result right after the apply, i get several cracks in the vinyl color printed surface after a couple of days.
Would the vinyl color not be the correct choice of paint?

You would have to check with an industrial ink maker to be sure you're using the correct ink. I can tell you you'll need to allow the spray painted piece to air dry for a few days before applying any clear coats or over printing. If you do clear coats or over printing before the enamel paint is fully dried it will vape off solvents through that over print or coat thus damaging it's finish.

But logically if you're using enamel paints then an enamel ink may be in order. But again, I would check with an industrial ink maker for this info. However, they may have you using the correct ink but you're printing it too soon after painting the rack surface.