Choosing the right substrate (surface) for your mosaic.
Mosaics can be applied to almost anything that doesn't move! (and no ladies this does not mean your husband!) Artists and hobbyists have covered everything from wine bottles to store mannequins, buildings, bathtubs and more. You can let your imagination run wild but there are a few basics you need to consider.
When choosing a substrate the main characteristic you're looking for is that is solid without flex and does not expand or contract with differences in heat or humidity. Although there are many adhesives that work with flexible materials in the end the surface will not be able to support the weight of adhesive, tesserae and the grout. If the surface has to much flex the grout will crack and the tiles will pop off. Surfaces must be solid, free of loose paint, wallpaper, dirt and grease, etc. and must be strong enough to support the mosaic. It may be necessary to scuff the surface of some materials by scoring or rough sanding it first to give it "tooth" that aid in so the your adhesive will stick to it.
Another important consideration is where will the completed piece be displayed or used when finished. Inside or outside? Do you live in a climate with freeze/thaw cycles or high humidity? Will it come is contact with water? All of these things can affect the surface and may in turn have a negative impact on your finished project. It is just as important to select the right substrate as is is to select all the materials for your project. Below you will find a list of the basic substrate materials along with recommendations for their use.
WediBoard - Wedi board is probably the most commonly used lightweight substrates among mosaic artists. It's a German product normally used in the construction industry as an underlayment for bathrooms, showers, floors, anywhere that needs waterproof material. What is it exactly? Wedi board is a foam board covered with a thin layer of fiberglass mesh and a cement coating. It is entirely waterproof and weatherproof, very rigid so it won't warp, and super lightweight. It can be used indoors and out in all climate conditions. Available in 1/4" and 1/2" thicknesses each sheet comes 3' x 5" (36" x 60") so you can often get many projects from one piece. Its easy to cut with utility knife and leaves a smooth edge that will need to be framed or covered. It is important to note you need to plan ahead when it comes to hanging. If you are not framing, installation of hanging hardware and edge treatment should be done before you begin your project. See the how to video below for simple instructions on hanging and edge treatment.
You can use most any adhesive with Wedi Board but is was created for use with cement based adhesives such as thinset. Please make sure you are using the correct adhesive for your project final display location..
One of the drawbacks to WediBoard is availability. It is not carried at your local home improvement store. Contact you local tile and flooring store to check for availability.
GoBoard, Durock Ultra Light, Kerdi Board and other foam core products - Similar to WediBoard all of these products are lightweight, rigid, water and weather proof, and tempertaure stable. All were developed for the building trades for showers and flooring underlayment and all of the above cutting, hanging, and adhesive instructions above for WediBoard apply. The upside here is that one or more of the these products can be found at most local home improvement stores. The same hanging and edging practices used for Wedi Board apply here.
Cement board - This is exactly what is says. It is a cement-based product formed in sheets and reinforced with fiberglass mesh. It is most often used to construct shower surrounds and as a substrate for tile floors. Cement board is weather and water proof, permanent, and readily available at your local home improvement center. Cement board is heavy and cannot support itself, it must be screwed in place or to another surface that can support it. When cutting the edge are rough and a bit uneven, you will need to plan for covering or trimming these edges. Thinset should be used as the adhesive when working with cement board. This is not typically a backer that you would use for artwork but rather one for construction or surfacing of walls and such.
Hardibacker - A brand name backerboard that is easier to cut and lighter weight than cement boards. A composite material of cement and cellulose, it is water and mold resistant and secures well with thinset. Hardibacker can not support itself and must be screwed in place to a firm backing. There is more than one type of Hardi Backer to learm more go to James Hardie's website, (manufacturer of Hardibacker). The is a wealth of information about the product there.
Wood - Although wood is readily available one must proceed with caution when selecting this as a base material. Wood is vulnerable to changes in humidity or temperature and can warp or crack, thus popping tiles and cracking grout. if you are going to tile a wood piece such as a dresser or table. Make sure that it properly sealed, free of loose or peeling paint, and sanded to aid in bonding. Wood elements from craft stores (frames, shelves, birdhouses, boxes, etc.) are ready for mosaics but are NOT suitable for outdoor use. We recommend Kilz. It not only seals but acts as a bonding agent for your adhesive. Do not use sealer's like Thompson's water seal, as they leave a waxy finish that prevents adhesives from sticking.
Treated and exterior grade lumber also is not a choice. The treatment that it receives is to prevent rot and does not prevent warping.
* Best advice - If you are using wood. Keep it indoors where the humidity is more stable and your piece will not get wet. SEAL IT! Use a high quality bonding primer such as Kilz.
Plywood - Although wood is readily available one must proceed with caution when selecting this as a base material. Even plywood is vulnerable to changes in humidity or temperature and can warp or crack, thus popping tiles and cracking. It may be used successfully indoors in smaller sizes and should be sealed with Kilz or similar primer. Multi-layer birch cabinet plywood is a good choice for interior art work.
Glass - Glass makes a great stable surface to work on and if you are using translucent materials you can create beautiful Sun Catchers, etc. Stained Glass makes wonderful tesserae. You can create the look of stained glass windows without the lead, solder, and the fumes. Old windows, table tops, votives, all make great bases for mosaics.