Appearing black, the dark-brown glaze covering the interior and exterior of this cauldron is suffused throughout with silvery "oil-spot" markings. The "oil-spot" effect was achieved by the application of iron-rich solutions to the glaze in a way that resulted in super-saturated iron compounds collecting into the desired silvery spots.
This rare "oil-spot" censer is apparently unique. Technical characteristics indicate that it probably comes from kilns near T'zu-po in Shantung province. Its dating has been confirmed with a thermoluminescent test.