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| Posted on 3/20/08 at 11:35 AM | |
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The answers you found are all spot on and helpful. But a couple of things that may help as well. The reason pre-flashing or pre-drying the garments before print seems to help some, is that... yes...it helps to rid the garment of moisture that is entrained in the dye. It does not get rid of all the moisture though. The prescence of moisture and the fact that you are putting the white down in two layers is the crux of the problem. You are trapping moisture that is still venting off, between the two layers. When it steams off due to the heat of the second flash its popping holes or bubbles in the second layer of white. The bubbles that do not pop all the way through are partially responsible for the raised bumps or "orangepeel". I say partially because the other portion of that is probably excessive squeegee pressure. After adding the stretch additive the ink is resiliant enough for the excessive squeegee pressure to not actually pop holes in the ink film. But the trapped air/gas bubbles are generally still there. By slicing a strip of this area out and magnifying the edge you can usually see what looks like a "sponge" structure to the two ink layers. The stretch additive makes the ink more flexible. You will still get some orange peel if the only change was adding stretch additive as it allows the ink to stretch enough to not have the gas bubbles blow holes in it. Since the ink with stretch additive is actually a bit tackier, that "pop" you are hearing is the soft tacky ink patch sticking to the back of the screen from the excess squeegee pressure. The flash only makes it dry to the touch. It is still tacky and carries a lot of heat back to the screen. My suggestion to help make this even smoother would be to either (a) go to a higher mesh count since you are going to be putting two hits of white on anyway...as well as increasing screen tension which will allow lowering of off contact... which will allow decreasing squeegee pressure and/or (b)...greatly increase screen pressure which can allow you to get away from two hits in the first place. that second one is actually a common technique and has been around, but it requires a great deal more tension, attention to detail of set up and very low off contact. the object is to release a thinner layer of ink (to keep the soft hand)...directly and only... onto the top of the shirt fibers (not pushed in at all) which will maintain opacity as good or greater than two compacted layers of ink. Ray [Edited on 3/20/08 by raygreenwood] | ||
 
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