So the larger of the two terra sig pieces came out of the kiln with two dark (symmetrically equidistant) patches at the base.
I'm unsure what caused them, but considering the base of the piece was constructed with thicker coils, I wonder whether it was caused because of the way the piece heated (and subsequently cooled). Originally, I wondered whether it was caused by glaze vapour from other pieces in the kiln, but the symmetry seems to suggest otherwise.
Attached videos to show how the patch is slightly shiny.
Didn't correct the colour temperature here. The photographs in previous post more accurately demonstrate the final colour.
