A water dropper is used for diluting ink. The ink consists of a mixture of oil and charcoal compressed into a small stick and then dried. For writing with this, the dried ink first has to be rubbed to a fine powder on an ink stone, and then diluted with water from the water dropper. The more water used, the greyer the ink produced. Since the sixteenth century water droppers have been made of porcelain in Korea, in many different kinds of design and in all sizes. They changed from being a simple object of use, into much-desired collectors' pieces, and they continue to be much sought after today.