Epson STYLUS PRO WT7900 Reference Manual page 24

Reverse White Print Mode – Main Clear Film Print Mode
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All color is applied first, followed by white
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Proofs are viewed from behind the printed surface
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Color is extremely vivid and clear compared to the Surface White Print Mode
Surface White Print Mode – Main Metallic Film Print Mode
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White is applied first, followed by all the color
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Proofs are viewed on the printed surface
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Color gamut is smaller than the Reverse White Print Mode
Two Different Printing Modes for White Ink
Epson Stylus Pro WT7900