Before you begin your mosaic it is important to consider carefully what adhesive you are going to use on your project. Use the wrong adhesive and you run the risk of your mosaic not lasting as long as it should.
The choice of adhesive is affected by a number of factors; the base you are using, the environment where the mosaic will sit, the materials / tiles you are using and whether the mosaic will be submerged in water.
To understand what is the best adhesive for your project you need to understand the different choices available and which one works best with different surfaces and environments. Adhesives are rated for different uses; indoors, outdoors, vertical, horizontal and submersible. To achieve the result you are after you need to select the right one for your application.
PVA adhesive (also known as ‘white craft glue) is commonly available and cost effective. Suitable for indoor mosaics only it dries fairly quickly, moderately water resistant, dries clear, non toxic and cleans up in water. PVA adhesives should not be used on any outdoor project. Weldbond is considered the best PVA adhesive by many mosaicists.
Cement Based Adhesives
There are numerous brands of cement based adhesives which can be purchased from hardware and tiling specialists. They come in pre-mixed and powder form, the pre-mixed ones are generally not as strong as the ones that you mix yourself. These adhesives are rated differently; suitable for horizontal, vertical or submerged water environments.
Well known manufacturers in Australia include Ardex, Laticrete, Mapei. The Dunlop brand manufacture a two part cement based adhesive called ‘Tile All’ that can be purchased at Bunnings and is suitable for use in submerged water environments, including pools and birdbaths.
Cement based adhesives need to rested before being used, this time is to allow the chemicals to interact. This time varies depending upon the brand so it is best to read the manufacturers instructions to find out how long.
You generally have about 20 minutes working time with a cement based adhesive so mix the adhesive in small batches. You can slow down the adhesive drying out by covering it with a damp rag when you are not using it.
Cement based adhesives are referred to as ‘Thinset’ in many mosaic books.
These adhesives are very strong, have a noxious odour and are difficult to work with. They work well on non-porous surfaces such as metal and glass. They have a short working period so they are not suitable for beginners. If you are using this adhesive make sure you are well prepared to work quickly.