Dark shirts tend to run a little higher then basic white garments and that's because they require longer prep times and a white under base.
Lets say you have a 3 color design but since it’s going on a colored shirt. it turns it into a 4 color design and this is because of the white under base. Whenever you print on a colored shirt you automatically have to add on a under base and screen which acts as a blocker between our ink and the garment dye.
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