Applying grout to slate wall tiles is more demanding than applying grout to floor tiles. 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. Make sure you follow these guidelines carefully.
Step 1 - Cleaning
Start off by cleaning the tiles from any residues and excess mortar. Wipe with a dampened soft cloth.
Step 2 - Sealing
Once the tiles have been allowed to dry, apply a coating of tile sealant on their surface with a small paintbrush. Coat only the surface of the slate tile and do not allow the sealer to get into the lines around the tiles where the grout will be applied.
Step 3 - Mixing the Grout
Next, you have to mix the grout. It is best to use unsanded grout. Also, try to choose a color which is similar to the tiles' color. Mix well until you achieve the desired consistency. It is best to add the water a little at a time.
Step 4 - Applying the Grout
Scoop a small amount of grout onto a grout float and apply it carefully in the space between one tile and another. A grout squeegee may also come in handy to press the grout down in the space. Use a damp sponge to wipe away any excess grout.