I explained to my customer - who was very happy with the choice of tile - that the fireplace would have be cleaned and sealed once the Slate tiles had been installed. This customer planned on having a coal fire installed following the tiling, but without a robust seal the Slate would be blackened by the coal and become difficult to clean.
Cleaning and Sealing an Oyster Slate Tiled Fireplace
Once I had successfully tiled the fireplace with the new Oyster Slate, I set about cleaning the area with an application of Tile Doctor's versatile alkaline-based cleaner, Pro Clean. The tiles were caked with debris and dust from the tile installation, but Pro Clean - which is suitable for use on most types of natural stone tile - quickly cut through the layers of dirt and left the area looking perfectly clean and ready to be sealed. My choice of sealer was Tile Doctor Ultra Seal, an impregnating sealer which soaks into and fills the pores of the Slate, thus preventing dirt - such as debris from a coal fire - from becoming ingrained in the stone. Ingrained dirt can make tiles notoriously difficult to clean, so it's always recommended that you have use a suitable sealer - and keep it topped up - to make your life easier when maintaining the appearance of your tiles in future.The sealer also enhanced the natural colours in the slate enhancing the look of the fireplace and the customer was very pleased with her new tiled fireplace with a robust seal in place she will not have to worry about its appearance becoming spoiled any time soon.
Source: Tile Installation, Cleaning and Sealing Service in East-Yorkshire