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Sorry, matey, this kind of grog is not something the English army used to drink.  Instead, it's a refractory material that's often used to make more durable casting molds. 

Grog usually refers to one of two different products.  One is pre-fired clay that has been ground and screened to a specific particle size.  This product is usually available at ceramic supply stores, and is also known as chamotte or firesand.

The term grog is also used to refer to ground up silica bricks.  (This type of grog is often called "silica grog".)  You can make these yourself by grinding bricks, but it's easier and safer to purchase it pre-ground and sifted by particle size.  Silica grog also tends to be more refractory than clay grog (it can withstand a higher temperature without deteriorating), and is probably the best choice for molds that will be fired at or above fusing temperatures for a longer period of time.

Grog can usually be added to any casting mold formula to increase durability.


Copyright 2006 Brad Walker.  All rights reserved.

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