In order for ink to be visible and accurately show the precise colors desired, it must be applied to a white background. On darker backgrounds, ink will be difficult to see, and it will be completely imperceptible on backgrounds that match its color. Put briefly, if the image being printed is darker than the surface of the fabric onto which it is being transferred, you should use light fabric heat transfer paper. If the image being printed is lighter than the surface of the fabric onto which it is being transferred, you should use dark fabric transfer paper.
Transfer paper for lighter fabrics is extremely thin and the white of the paper transfers to the fabric as a transparent layer that is almost imperceptible on the light fabric. Dark fabric transfer paper is thicker and more opaque in order to prevent the color of the fabric from showing through the image. The transfer paper used for lighter fabrics is thin enough to result in a texture that feels like a screen print; the transfer paper used for darker fabrics, however, is thicker and can feel a bit like a sticker on the fabric.
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