What Mosaic Base Should I Use?

Mosaics can be applied to most surfaces, including bowling balls and styrofoam forms. This article looks at common mosaic bases, their pros and cons and what adhesives can be used. Ultimately the choice of a mosaic base or substrate is determined by many factors, including the mosaic's intended use, location, type of project, cost and individual choice.

Surface Preparation Tips

Make sure your surface is clean before you start
Check if your surface needs to be sanded and primed to allow the adhesive to grip the surface correctly.
A primer works to reduce the porosity of a substrate; it doesn't eliminate it. It helps to stop the adhesive from drying out too quickly and destabilising it. It also creates a clean surface for the adhesive to stick.

Download a copy of the instructions for What BASE IS RIGHT for Your Mosaic Project below.

TYPE OF BASE	INDOOR	OUTDOOR	SUITABLE ADHESIVES
MDF (Medium Density Fibreboard) Made from compressed and glued pieces of sawdust, it is dense and heavy and will not warp. Venerability to water damage can't be used for outdoor mosaics. The bonding agent used to make MDF pose health risks; a safety respirator should be used when cut. Popular for craft projects because it's easy to use and cheap. It can be primed or sealed before use.			PVA Weldbond Cement Based Adhesive Liquid Nails
PLYWOOD Plywood is made from thin sheets of wood that are laminated together. Susceptible to water damage and not recommended in areas exposed to water. Plywood needs to be sealed. Seal the mosaic well and paint all surfaces that aren't mosaiced. Easy to cut and screw, able to be shaped into different forms, cost-effective, resistant to splitting and warping. It needs to be primed or sealed first.			PVA Weldbond Cement Based Adhesive Liquid Nails
HARDWOOD It is not a good material for mosaics because of its vulnerability to moisture and decay. Do not use it on an outdoor mosaic. Wood can be used on small indoor mosaics such as mirrors or plaques. To prepare wood seal back and edges or paint. The bigger the mosaic, the thicker the wood must be to prevent it from warping. It needs to be primed or sealed first.			PVA Weldbond Cement Based Adhesive Liquid Nails
TERRACOTTA A good choice for a mosaic base due to its weather resistance Ensure that the surface is cleaned and a coat of sealer is applied. Sealing the terracotta will help stop it from absorbing water from the adhesive and the grout from drying out too quickly. It needs to be primed or sealed first. A tacky adhesive is good for holding your tiles on curved surfaces (for example, a cement-based adhesive).			PVA & Weldbond - indoor projects Cement based adhesive - outdoor projects
CEMENT / CONCRETE Excellent surface to mosaic, especially exterior mosaics. Robust, rigid and weatherproof. Stepping stones can be from wet cement poured into moulds or cement pavers. Tiles and tesserae can be laid directly into wet cement. It needs to be primed or sealed first.			Cement based adhesive
GLASS Glass is highly effective when using transparent tiles. Clean the glass with methylated spirit before mosaicing. Ensure the glass tiles adhere with smooth side onto glass with plenty of clear silicone. Wipe away excess with a sharp object, and press down well to ensure no air bubbles.			Clear silicone Weldbond Adhesive Mac Glue
METAL Lightly score or rough up the metal surface before adhering the tiles. Check the metal surface for rust. Consider the weight of the mosaic when finished. Metal can expand and contract under temperature extremes, which may cause the grout to crack and tiles to fall off. Consider covering the metal with a wire mesh fixed with screws and then applying a coat of cement. Some examples of metal objects to mosaic: shovel, bath, pot, table & bucket. It needs to be keyed or roughed up and primed.			Two part epoxy Araldite
COMPRESSED FIBRE CEMENT (CFC) High-density fibre cement sheet Difficult and messy to cut Excellent for outdoor murals and tabletops Tough, durable substrate, will not warp, weather resistant Apply a coat of primer to help the adhesive take hold			Cement based adhesive (Thinset)
MARMOX A lightweight, economical substrate. Made from waterproof extruded polystyrene, faces with a fibreglass mesh embedded into a cement polymer on each side It is light and tough but can be cut with a sharp knife; no power tools are needed. Not prone to warping and waterproof, suitable for outdoors. To make Marmox waterproof, coat the edges in either cement or a cement-based adhesive.			Cement based adhesive (Thinset)
STYROFOAM FORMS Great for creating 3-dimensional shapes Don't use adhesives that contain solvents, as they will dissolve the styrofoam. Weldbond works well as an adhesive for indoor smaller-sized projects, with the tiles and tesserae being directly applied. For outdoor or larger projects, wrap the styrofoam form in wire mesh, then apply a layer of cement to serve as a base for the mosaic. The cement can also be applied directly to the form in smaller projects. Not suitable for outdoor projects unless covered with a protective layer. It can be coated in a layer of cement-based adhesive to give it extra rigidity and durability (important for outdoor mosaics).			Cement based adhesive (Thinset)