Could you please suggest a colour that isn’t visible through the fabric of a T-shirt? I need to print on the inside of the collar without the writing showing on the other side.
The problem isn’t the ink, assuming it’s not really runny.
The problem is the thickness of the T-shirt and the pressure applied on the squeegee.
In general, since any ink that’s soaked up by the material, from a coverage standpoint, is completely wasted, it’s always good practice to control and limit the pressure applied on the squeegee: two light, rapid movements are better than a single, heavy movement.
Indeed, on screenprinting courses, to check if the squeegee movement has been done correctly, the T-shirt is inspected from behind: if the ink isn’t visible, the movement was fine, if the ink is visible, the squeegee pressure was too great.
Obviously, some of the T-shirts that are available to buy are made of very thin fabric, so thin that it’s impossible to prevent the ink from coming through, no matter how light the movement is.