The white on my tile is dependent on the color of the clay itself because I work on the raw clay, after which I apply a clear glaze on top. Actually, Mr. Cranky is the glaze applier, but that is beside the point.
Dal tile, mechanical, ram-pressed
The point is, sometimes a client has commercial field tile that they want to match and I am limited in the shade of white that I can offer. This issue came up recently when a client ordered a few pieces to go with some tile she had already purchased and was dismayed to find they did not match well enough. The client was so sweet and so in love with the little ducklings that I decided to try decorating on top of the mechanical tile she had.