I have had a few questions recently about thinsets that are bleeding into natural stone tiles. A customer called while installing a dark granite tile and was concerned that the white thinset that he was using was entering and discoloring the tiles. I will tell you guys exactly what I told him.
When installing, and caring for, natural stone flooring, it is very important to use thinset, grout, sealers and cleansers that are specifically designed for your stone. In this case, the customer was using a thinset designed for porcelain tiles. Porcelain thinsets tend to be a thinner mixture and because your natural stone is a porous material, it can have a tendency to bleed into natural stone. When installing stone flooring, ensure that you are using a thinset that is designed for natural stones. Also be sure to mix the thinset exactly as the manufacturer suggests. If your mixture is too runny, you risk bleeding and seepage.
So, to avoid having your thinset bleed into your tiles and discolor your new floor, ensure that you a) are using the proper thinset and b) have mixed it to the correct consistency. This will help ensure that your tiles stay the same vibrant color that they were in the box and give you many years of beautiful stone floors.