Testing underglaze for nerikomi

While waiting for mason stains to be shipped, I wanted to see if there was a more cost effective way for me to make colored clay. Underglaze is made of clay and colorant, whilst overglaze is made of a mix of glass and other minerals. Typically for nerikomi and agateware, clay is colored directly with colorant (usually mason stains), but I think if you add enough underglaze color to a clay it could pick up the colorant.

I mixed buff stoneware (maybe not the best choice of clay - white would be best regardless of technique) the same way you would mason stains, dumping the colorant into an indent made into the clay then wedging it. I didn't measure, just adding enough until I noticed a difference in color. The white clay didn't ever seem to really change color.

Using an extruder, I pushed the colored clay into long triangle shapes. I was aiming for a very simple alternating black and white triangle pattern.

There’s a very subtle difference in color between the clays, but enough so that I could tell where to place them in the pattern. I cut them into about 2 inch bits and stacked them, spraying them with water between layers so they stuck together.

I upped the exposure on this picture of a cup I made out of the slab from the stacked clay. It still needs to be fired with transparent glaze. Usually at this stage, underglaze becomes more vibrant, but it’s very subtle still. It’s probably not a great method for nerikomi making going forward.