Grouting a mosaic can significantly enhance its beauty and durability. To get started, ensure that your mosaic is fully set and dry; typically, this means waiting at least 24 hours after laying the tiles.

First, prepare your grout according to the manufacturer's instructions. Mix it to a smooth, creamy consistency, being mindful not to overwater as this can weaken the final product. Once mixed, use a rubber float to apply the grout, pressing it firmly into the gaps between the tiles. Work in small sections to maintain control and ensure an even application.

After filling the joints, take a damp sponge and gently wipe over the surface of the tiles, being careful not to remove the grout from the joints. Rinse the sponge frequently to avoid smearing grout onto the tiles. Once you've wiped the surface clean, let the grout set for about 15 to 30 minutes before buffing the tiles with a dry cloth to remove any remaining haze.

Finally, allow the grout to cure fully over the next few days, following the advice on the product for best results. Your mosaic will then be ready to shine, showing off the intricate patterns and colours you’ve painstakingly created.