Grogs are raw materials that contains high amounts of silica and alumina, and can be added to clay bodies for increased strength and/or texture. Because grog can add extra body and support to clay, it is a common additive in clays that are used for handbuilding or sculpture -- often, in large-scale artworks, it is grog that allows the clay to go large! Grogs are also helpful when added to clay intended for wheelthrowing, particularly on a larger scale - the grog gives a piece support. High grog content clay bodies are not always ideal for throwing, however, because the grittiness can be too rough on the hands and can cause skin irritation. As a result, potters who work on a wheel will often prefer clay with little or no grog, or if they do decide to add grog, they like to use grog with a smaller mesh size.
Adding grog to clay produces a number of benefits. For one, grog will reduce the degree of shrinkage that clay experiences during drying and firing -- that’s because many grogs are made up of ceramic materials that have already been fired (and then pulverized), so as a material, they’ve already done all of or most of their shrinking. Secondly, because the grog creates a more porous composition, clay with grog dries more evenly. Because of this tendency to encourage clay to dry more evenly, adding grog to a clay body can help quite a bit to prevent cracking.
Grog is available in in various mesh sizes. With mesh, the larger the number, the smaller and finer the particles. For example, a 100 mesh grog is coarser than a 200 mesh. The finer the particles are, the stronger and more dense the clay body will be. Like all of our dry materials, we sell our grogs by the pound, so if you are interested in testing some different mesh sizes wedged into a claybody, we can do that.