The firing of several vessels stacked on top of one another, or the firing of the fired vessels. In this case, “buds” or “needles” made of refractory clay are used between the vessels to prevent the glaze from fusing to the glaze of each vessel. As a result, the fired pieces leave traces of the buds and lack glaze in these areas. In other cases, when vessels are stacked one on top of the other, the part of the vessels that touches each other is sometimes left unglazed, leaving a serpentine pattern. Both of these techniques are found only in old pottery, where kiln-filling methods were not developed, and in modern coarse pottery, which is intended to be inexpensive.
