Recently I heard from someone who liked the feel of throwing a white stoneware however the specific application was using a glaze called 'butter' which comes out a beautiful creamy white to light brown. It looks better on a clay body which contains some iron as it produces iron spots and helps bring out the brown color. White stoneware has less iron and impurities than stoneware so to get the butter glaze to come out in a white stoneware our experts suggested to try mixing iron oxide into the clay we were preparing for the day beginning with a small quantity such as 1 teaspoon. Iron will help to bring out variations and brown spots in the glaze.
Iron Oxide. This comes in many varieties and can provide a wide variety of colors under different firing conditions. Types of iron oxide are red iron oxide, black iron oxide, and yellow ochre. At earthenware temperatures, up to 4 percent oxide will produce amber and honey glazes.
At stoneware temperatures it can be applied directly to stain the clay surface. It is often used in this way to highlight textured surfaces. Can also be added to glazes.
can be fatal and should be avoided.
especially in the fired state can shed invisible floating fibres that have similar effects to asbestos.