Mosaic Substrates. What is a SUBSTRATE ? A substrate is a term used in mosaic-making for the base or board that we place our mosaic design onto. It could be wood, concrete, tile-backer board, metal or even plastic....but ......not all make suitable substrates, especially if you are making a project that will go outdoors. Some may warp, flex, absorb moisture or break down over time, so it's important to understand what will make a good substrate 👍 and what won't ❌ I'll be covering substrate choi