Preparations, Surfaces & Methods to Mosaic Art
Mosaics can be laid on to a variety of different surfaces, and, as long as the correct procedures are followed, they will be hardwearing and waterproof and have a professional-quality finish.
Traditional mosaics were laid on to a cement bed. Now we can also mosaic on to all sorts of different surfaces, such as wood, old furniture, plaster, ceramic, terracotta or fiberglass.
Unless working with a sculptured form, you should work on to a flat, even surface for a professional-quality mosaic. Uneven surfaces should be sanded down. If working on to cement, a new surface should be laid: self leveling cement is an easy option.
The base or surface should be rigid. For example floorboards are flexible, and any mosaic laid on them will lift it there is movement. So a thin layer of wood should be cut to fit and screwed in evenly to cover the entire surface. Wood is a very good base, but if the mosaic is going outside or will come into contact with water, the wood must be exterior grade, such as marine ply.
The priming of surfaces is very important.
Most working surfaces, such as wood, concrete, terracotta urns, old furniture or plaster, are porous, so the surface must be sealed with diluted PVA (white) glue. This greatly improves the sticking power of adhesive and makes the final mosaic more hardwearing and waterproof. Before sealing, it is important to ensure that the surface is clean of all loose debris and hair. Smooth surfaces, such as wood or fine plaster, should be scored with a sharp implement, such as plastics or existing tiles, a special two-part resin primer can be brushed on to provide a key. It creates a surface to which an adhesive can easily attach.
Diluted PVA glue can also be used to coat terracotta pots in order to make them frost-resistant.
Once the surface has been properly prepared, there are various ways to fix the tiles. Choosing which technique to use depends partly on where the mosaic is situated and partly on personal preference. The direct method involves placing the material straight on to the working surface. The indirect method involves creating the mosaic off-site, then installing it.
The Direct & Indirect Method
There are two basic methods for making a mosaic: the direct method and the indirect method. The direct method is the most obvious technique. The mosaic pieces are fixed directly in place onto the base, the right way up, then grouted. It is a one-stop process, and what you see is what you get.
The indirect method, or reverse method involves constructing your mosaic upside down on a sheet of brown paper. This is an interim measure that allows you to work on the mosaic in a comfortable position away from the final site. The indirect method produces a smooth, level surface, particularly useful if your tesserae are of uneven depths.
Step 1. Transfer your design in reverse onto brown paper using diluted water-soluble white glue (one part water one part glue).
Step 2. Spread a ready mixed cement based adhesive over the base of the mosaic's final site then comb through with a 3mm (1/8-inch) notched adhesive spreader. Try not to take too long over this, the adhesive can became tired and not behave properly.
Step 3. Place the papered mosaic carefully onto the bed of adhesive, and press it down thoroughly, using a small, flat board to help.
Step 4. Leave the adhesive to set completely, then dampen the paper using a sponge and warm water. After a few minutes, carefully peel the paper off. The exposed mosaic can then be grouted. You may also consider pre-grouting the mosaic before it is set into the bed of adhesive.