The bright bursts of cobalt blue and turquoise on the body of this jug were initially colorless when they were applied and did not gain their final hue until after firing. Ceramics from the Islamic world, but especially medieval Iran, often feature incongruous splats of blue, turquoise, or green that perhaps were originally accidental but were later adopted as part of a vessel’s decoration. Here the alternating streaks of blue and turquoise are a continuation of the "accidental" drip made intentional.