QUESTIONUsing Different Tiles Together - I was given a bunch of different tiles that were left over from various tiling jobs. Without any original packaging for reference, how can I determine each tile's hardness rating? I want to redo my floor and am willing to mix and match, but shouldn't I make sure that all the different tiles I use have the same hardness rating?
ANSWERANSWER - Using different types of tiles in the same installation can be done if you like the blend of colors. You do need to adjust for different facial dimensions and different thicknesses from one tile to the next.
If they are all floor tiles it probably isn't a big concern if the hardness of their glaze and body are different, as long as they are not significantly different. If they are more recently made floor tiles they are probably all vitreous or impervious type of tiles. I assume they are all glazed floor tiles. Unglazed floor tiles would not be a concern even if they have different harnesses, because they are all designed to be more durable.
Old Italian button-back glazed floor tiles could be a concern because those tiles had very porous bodies that were not as hard and they tended to be more prone to chipping. The rule was if the hardness of the glaze was more than 2 calibrations different than the hardness of the body that it would tend to be prone to chipping. You can use a Mohs Hardness kit that uses different minerals to determine the hardness of a tile body or glaze by scratching it with the mineral. You can have a testing laboratory do it, but it will cost $150 or so for each tile you test.
A simple qualitative test to perform would be to put a dimes amount of water on the back of the tile and if it readily absorbs then it is a softer tile. If it sits there and doesn't absorb right away then it would be a harder tile.