Trouble with porcelain

[Big Red]

My porcelain is almost like flagstone; unlike the original sample, the tile is a greyed out brick red when dry and becomes the rust of the original dry sample, (as desired) when wet. Although apparently sealed, it seems to have a tooth or be almost gritty on the surface. Is there any matt or satin enhancer that can be applied to the surface that will not peel? It is in a shower enclosure. I have yet to see one that is not for natural stone applications and go so far as to say "not for ceramic or porcelain tile.

[jadnashua]

If it is truely porcelain, do not try to apply a sealer. The very nature of porcelain is that it is very hard and essentionally, does not absorb much of anything. The only porcelains that might need a sealer is if it is polished - this opens pores in the surface.