|Monthly Tech-Tip |
Here is a good reason not to have single-temperature-tunnel-vision when evaluating or using a clay body or clay material. This high-iron clay looks great at cone 3 or 4 (the bottom bar is cone 5 and out-of-place). But by cone 5 the solubles (invisible at lower temperatures) begin to melt. Shortly after it rapidly descends into serious bloating and then melting by cone 8.
When clay materials and bodies bubble as they melt or over fire. This normally happens in raw materials that contain particulates that produce gases during firing.