A mosaic is a picture or design made from small bits of materials, and mosaic tiles date to Roman times. Mosaic tiles can be regularly shaped square tiles or broken tiles that the artist arranges by hand. Tile artists use broken pottery, glass, beads, gems, metals and other materials to transform the tile surface into tile art. Commercial mosaic tiles are mounted to a mesh sheet, come in uniform sizes and are simple enough for a do-it-yourselfer to install, although the inside corners can be tricky.
Position the last two mosaic sheets that will take you into the corner of the tiled area. Lay the sheets next to each other on your work surface and bed the tile by moving the tile sheets into close proximity, about one grout line width apart, so that projecting tiles from one sheet overlap mesh backing on the adjacent sheet.
Measure the width of the space left on your wall. Carefully mark the measurements on your cornering mosaic sheet along the edge you will need to cut. Use a piece of tape to mark the cut lines on the tile sheet, and measure several locations since your corner may not be square.
Turn your mosaic sheet over and cut the mesh between the tiles that are on the waste side of your tape using a utility knife and heavy scissors. Cut through individual mosaic tiles that cross the tape line using a tile nipper. You should end up with a straight line of tile at the corner of the wall.
Trowel your thinset mortar onto the wall from your last installed tile to the corner. Drag the V-notch side at a 45-degree angle to scrape off the excess mortar. Flatten the V-notch if you are installing glass tile, as the lines of the notch will be visible behind the glass.
Install your two sheets of mosaic tile. Bed the mosaic pattern together. Use spacers as necessary. Tap with a rubber mallet and block to seat the tiles well into the mortar. Double check that the mosaic tiles are level and straight and that none have fallen off.
Install the adjacent tile wall by marking the center line of your tile work and moving toward the corner or ends. This means that your first mosaic corner will be finished after the majority of your second tile wall is complete. When you fit the last two mosaic sheets of your second wall toward the corner, follow the same directions as above. The inside corner edge of your final tile sheet should be the width of one grout line away from the existing tile face on the adjacent wall. This will allow you to grout between the edge of one sheet and the face of the other sheet to create a clean finished corner. Make sure your tiles are aligned, level and straight.
Allow the thinset to dry 24 to 48 hours before grouting.
Mix grout to the consistency of frosting. Allow your grout to sit for 5 minutes. This will help the grout spread more easily.
Remove the grout spacers. Use a rubber grout float and apply grout to the tile. Press grout into the corner to fill the gaps between the tiles. Drag grout across the face of tiles at a 45-degree angle to fill the grout lines. Move your float at different angles to ensure that the grout lines are filling up. Gaps or bubbles in the grout indicate holes and must be filled.
Wipe and wash tile within 15 minutes of grouting or the grout will stick to the face of the tile like concrete. Use a clean sponge and bucket of water. Clean the sponge between each wipe and change the water frequently. Wipe the tiles until the grout becomes firm and the haze on the individual tiles is minimal. It is often a good idea to have one person grouting while another person cleans and finishes the grout and tile.
Allow the clean grout and tile to dry for 24 to 48 hours before using the surface.
Apply a grout sealer once the grout has cured. Paint the grout sealer onto the grout lines with a thin paintbrush.