Natural stone tiles such as granite, marble and slate are popular on floors and walls. But if you are not careful during the work, you risk the delicate stone becoming discoloured. This is due, among other things, to so-called “sweating”, where the part of the tile that is in closest contact with the grout or glue becomes darker and takes on a wet appearance.
You minimize the risk of discoloration by choosing a sealant or glue that is chemically neutral to the stone. Always make sure to make a sample before starting the task itself – the composition of the stone can vary. If you want, for example, an elastic joint, it is recommended to use a suitable MS-based joint compound or neutral silicone joint compound.
Read more about the right choice of sealant and glue for natural stone here:
http://www.danalim.dk/fileadmin/editors/Saadan_Goer_Du/dk/Natursten.pdf
