By sealing your slate tiles you are blocking the pores of the stone this will then enable the grout to float over the pin head sized holes on the stone not stick within the pores the grout should now be easily removed when it is applied you are now ready for grouting the slate tiles.
How to grout slate tile on wall.
How to grout natural stone tile.
Applying grout to slate wall tiles is more demanding than applying grout to floor tiles.
Reload the float and continue to apply the grout to complete the first section.
Sweep diagonally across the tile forcing the grout into the joints.
Natural stone tiles such as granite marble or slate are attractive options to consider when remodeling.
You will need to be sure to give the tiles sufficient time to dry and must be careful when you work with the tiles themselves.
Start off by cleaning the tiles from any residues and excess.
How to install grout slate tile.
Step 1 cleaning.
The beauty of the stone natural is highlighted when used.
Make a second pass with the float holding it at a steeper 70 to 90 degree angle almost perpendicular to the wall and scrape off any grout residue from the faces of the tiles.