Be sure to clean off any dirt or debris from your base before you use it. Use a damp sponge to scrub off any stubborn debris. Dry the base completely before you start applying the mosaic pieces to it. Your base can be any shape, but be careful with very extreme curves because you will need very small mosaic tiles to fill the curves. The best mosaic base for outdoor mosaics is concrete because it is the most weather-resistant. You can find thin concrete boards at your local building material store. A mesh metal pizza tray works especially well for making decorative glass gem mosaics. Terracotta bases are more risky for outdoor mosaics since they can be susceptible to freezing damage. If you want to make a mosaic on a terra cotta pot, for example, either take the pot inside in cold weather or apply several coats of sealant when you are finished to protect it from the elements.
Consider the size of your mosaic base when collecting your mosaic pieces. If you are unsure, scatter the pieces across the base. They should be able to cover it fully. If you are reusing materials for your mosaic, be sure to clean off any dirt or debris with soap and water. Let them dry completely before you begin the project. You can also add other objects or decorations to your mosaic, like small ceramic flowers. You can also used smashed china plates as mosaic tiles. Break one plate at a time with a hammer inside a plastic bag. Use a tile nipper to break the plates for more control over the sizes and shapes of the pieces. You will need 5-7 plates for a medium-sized mosaic, about 20 by 24 inches (51 cm × 61 cm). Cups don’t work as well for mosaics because they don’t end up making flat pieces so they are harder to arrange and glue down. [3] X Research source Round glass gems are a kid-friendly mosaic tile because you won’t have to worry about sharp edges. You can find the gems in your local craft store. They are available in many different colors and sizes. [4] X Research source
If you’ve sketched something on paper first, transfer your design onto your base using tracing paper.
You can further break your pieces with a hammer or tile nipper if need be.
If you are making an outdoor mosaic, make sure your adhesive label states that it is water-resistant. For mosaics that will regularly get wet, like shower floors, use thinset mortar. [7] X Research source Acrylic-based adhesives are easy to use and very strong and good for slippery surfaces like ceramic and glass. Epoxy resins work well on metals, but they can be messy to use and smelly.
If you have a powdered adhesive, mix it up outside and wear a dust mask so you don’t inhale the dust particles.
You can also put the adhesive directly on each mosaic tile as if you are buttering it like a piece of toast. Apply the buttered piece directly to the foundation and press down to affix it in place. This also works well if you have an adhesive that comes in a squeezable tube.
If you are using concave mosaic pieces, like shells, coat the underside of the shell with adhesive and fill the body of the shell with adhesive before you place it on the base.
Try to wipe the excess mortar as soon as possible after its set. If you wait until the adhesive cures completely (usually another 24 hours after it is set), it will be very difficult to wipe off the excess from the tiles. If you used traditional mortar, 24 hours is usually enough time for indoor mosaics. Outdoor mosaics will need to set for 72 hours. Acrylic adhesives and epoxy resins usually take between 12-24 hours to set completely.
If you used very textured or porous pieces, like shells or very uneven stones, you don’t need to grout your mosaic. If you are in doubt about the grout color, black is usually the best choice, and pure white often drowns out the mosaic design. If you want a lighter color, try a cream-colored grout.
If there is any stubborn grout residue left on the mosaic, or if you wait too long after it sets to wipe it off, clean the excess grout off with a clean lint free cloth or a piece of crumpled newspaper. Remove big pieces of grout stuck to the mosaic pieces with a non-scratch nylon scouring pad or a small wooden stick.
Let the sealant dry before using the mosaic. You can also get a matte finish sealant if you don’t want your mosaic to have a glossy sheen. Apply at least 2-3 coats of sealant to protect outdoor mosaics. Let the sealant dry between coats.
