Select the material you wish to use. Pieces of material used in a mosaic art are called tesserae. I used white sea shells
Pick the foundation to adhere the mosaic tiles on. I used an old pewter plate
Prepare the tesserae: I use a hammer to break the pieces. Make sure the pieces are clean of any dirt or debris before laying them out.
Mix mortar per manufacturer recommendations. Apply it to the pewter plate using a trowel or spatula. While still wet, gently affix the mosaic tiles by pushing them into the mixture. Starting in one corner and work across. Make sure you leave enough space between pieces for grout.
Let the mortar set. Time varies depending on usage, so follow manufacturer recommendations. For pieces in your home, the timing is roughly 24 hours. Outdoor mosaics will need to set for 72 hours. Clean the mosaic tiles once more to clear away any extra mortar that may have risen to the top.
Prepare the grout mixture. Grout comes in many colours and there are colours you can add to the grout to change the coloring. Choose a colour that accents your mosaic. Mix the grout by following the instructions provided by the manufacturer
Apply the grout using a spatula. Fill in the creases between the tiles. The grout should cover the mosaic enough to fill the gaps.
Let the grout set for 20 minutes, or the time advised by the manufacturer. Wipe the mosaic with a clean sponge and warm water. Rinse out the sponge regularly as you wipe away grout from the surface of the tiles.
Seal the mosaic with varnish. This will coat the tiles and safeguard against damage, especially for outdoor mosaics subjected to fluctuating temperatures and adverse weather conditions. It also will give a high gloss shine that will make the colours stand out.