Incense Clocks: Burning Time in Medieval Japan

Before the introduction of mechanical clocks with pendulums and gears, people around the world used a variety of ingenious devices to mark hours and keep track of time.

Most people are familiar with hourglasses, water clocks, and candles, but fewer people outside of Asia have seen (or used) an incense clock.

Incense clocks originated in China or in India (there are arguments, and evidence, for both) and spread to Japan by the 8th century (if not before). While the simpler clocks used sticks of incense that took known periods of time to burn, more elaborate clocks involved setting patterned lines of chipped or powdered incense on a bed of ash.

First, the bed of ash was cleaned, dampened slightly, and tamped down to provide a smooth, level bed. A stencil was rested carefully on the ash, and the prescribed amount of incense poured into the open areas in the stencil. After carefully tamping the incense onto the ash, the stencil was removed, and the clock was ready.

The incense trails consisted of patterned lines, with markings to indicate hours or fractions thereof; when the incense had burned as far as the mark, the indicated amount of time had passed.

The clocks, and the incense tools, were made by artisans – and while the tools and casings could be quite elaborate, others (like the ones above, which sit on display at a small museum in Magome, on the old Nakasendo Road) were more humble, and intended for use as part of daily life.

Specific types of incense, with known burn rates, were used to create the patterns. While some of the patterns were fancy, most were simple lines, spirals, or zig-zags:

As an added bonus, incense smoke helped drive away insects and prevent both bugs and other pests from taking up residence in the thatched roofs that were common in Japan during this period. A winning situation all around.

Do you like unusual timepieces? What’s the strangest–or most beautiful–clock you’ve ever seen?