What is Substrate?
Well basically it is the stuff you glue your tesserae and other mosaicing media to. It's the base or foundation for all your mosaic works of art.
Examples of Substrate Materials:
Wood of all types.
What Can Be Used For Substrate?
This is a bit of a tricky subject. You can use as substrate anything that will allow you to glue things to. Some things are easier to stick things to than others though, for example it is much easier to stick to wood and hardboard than it is to ceramics, glass and metals. These harder substrates need specialist glues to get them to stick.
I tend to use a lot of pre-cut wood such as keyring blanks and small wooden chests, but I do use hardboard as well. I have had immense difficulty with glass because finding specialist glass glue is not easy. Any porous material can be used, although I would definitely prime everything you use as a substrate beforehand.
How to Prepare Your Chosen Substrate.
A lot of the preparation depends on the type of substrate you use as different textures need different techniques. For all my wood, glass and ceramic mosaicing I prime with a 50/50 pva glue to water mix. It just fills up any holes in the substrate and gives a nice smooth surface to work on. I prime my pieces, then colour them in using felt tip pen. When the pen is dry I spray a varnish over the top of that to seal the colour in place and then I start work when that varnish is dry.
You also need to check your substrate and make sure it is straight and even. Possibly you may have to sand down materials left behind, for example if you have a piece of ply board that you are cutting to coaster size you might need to smooth down and saw marks or rough bits. Check that what ever surface you use, it is clean and dry, free from any grease or oils and as smooth as possible so you do not have to tile over bumps (very annoying I assure you.).
Make sure you leave your substrate for at least 24 hours after priming or varnishing the colours in, to be sure it is completely dry. I tend to prime all my new substrates together at once, then the next day start colouring in, when that is done I leave the piece for another 24 hours, varnish it and leave it for another 24 hours before I start work. I do, however tend to get large amounts of things at once so there is always something drying somewhere, something to be primed and so on.
Finishing Up With Your Substrate.
The last thing to say about your substrate is to make sure it is all covered up if possible. Returning to the 10 x 10 cm coaster, when you have finished everything on the front, make sure you tidy up the sides and cover the base up with a backing material such as felt. This makes the end product look very professional whether you intend to sell it or keep it yourself!