Grog, Sand, Paper and More: Clay Additives and Their Uses
Have you ever been shopping for clay, and noticed that you could buy it with "paper", or "grog", and wondered what that means? Wonder no longer! We've put together a list of the most common clay additives and what they are used for.
Grog is fired ceramic material that is ground up through different-sized meshes and then added back into a raw clay body. The most common form of grog is smaller mesh sizes (around 100M to 80M) that look like speckled sand. You can also buy it in large mesh sizes (30M to 60M) for a coarser consistency. Grog is added to get the clay more strength, which is good for building large items.
Be aware that extra grit, like grog and sand (below), can be rough on your hand when you are throwing.
Sand has the same added strength as grog when you're building larger or taller forms. But since it is used as an ingredient in both clay and glaze, adding too much can cause fit issues between the clay body and glaze.
Be aware that beach or landscaping sand may have contaminants that affect the firing results as well. Sand purchased from a clay or refractory company is free of these impurities, and is a much better way to go.
Clay with paper pulp added is called paperclay. Paper pulp mixed into clay helps give the greenware strength (for sculpture and building large pieces) without adding weight to the fired piece.
Paper clay is quick to mold and has a strong odor during firing. If you fire in a poorly vented area, you will potentially set off smoke alarms or disturb others with the smell of the burnout.
Be very conscientious of your paper-to-pulp ratio because the paper will smolder in the kiln.
Nylon fibers added to a wet mixed clay help add structural support to very large pieces. The fibers are chopped into short sections so large stars don't cause problems while working.
These fibers don't wedge into clay easily. It’s best to add this to a wet slurry and then reconstitute the clay into a workable state. A little goes a long way. If you’re using a commercial clay mixer or pug mill don’t add too much at a time, it can jam the equipment.
Mason Stains are a great way to add different colors to your clay body.
Generally speaking, you’ll want to use a ratio of one part stain to ten parts clay. This means if you are using 100 grams of clay, you will want to add at least ten grams of stain.
Unlike the much softer black and red iron oxide, this material is useful in granular form to introduce speckling into bodies and glazes.