* - In order to ensure that overpainting layers will adhere strongly to the primer, many primers have a "tooth", or "micro-texture" for the paints to grab on to. This is achieved by adding small, inert, texturizing particles to the primer. Standardly, these are made of crushed minerals like ground silica (ultrafine sand) or a coarse grade calcium carbonate such as marble dust. These particles are exremely sharp, and they wear out fine brushes very quickly. So we searched for a better particle! Our particles have the strongly angular shape needed to grip paints, but with edges and points which are slightly rounded to spare your brushes.