Because the uncoated side of the board has an open structure, it will absorb more of the ink, printed on the board. When printing on the reverse side of the board the ink will simply 'sink in' more than when the artwork is printed on the gloss side of board. This might affect the outcome of your artwork. Colouring, especially darker parts of the print might have less contrast. A heavy print on backside board also needs a longer drying time before we can use the board to fold sleeves. The drying time is very important, as dark print can cause marks on the light parts of the print. When we print on the reverse side of the board, we varnish it with a standard matt varnish which enhances the fixation.