Doko Copper Vessels (銅壷)
Doko' are utensils used to heat water and warm sake by placing on braziers. Heat obtained from charcoal heats water which has baths for semi-submerging sake bottles for warming. Two pipes are incorporated into the unit which make it resemble a balancing kettle or bathtub. The unit is made of copper which conducts heat well. Since the days of yore it has been said that water in 'Doko' heating units never goes bad; however, this is because of the sterilizing effect of the copper ions.
A large section of that part of the unit which is heated is designed to conceal the charcoal which is placed below. The exterior of the section designed to conceal the charcoal is shaped like a dome with an open ceiling. The upper sections of the unit often incorporate a built-in kettle stand. The units have two layers: the internal section being full of water which is heated by the charcoal. Built to be buried in the charcoal directly below is a u-shaped pipe which makes it comparatively easy to control the charcoal by use of metal chop sticks. The place at which the pipe and hot-water bath section come together is slightly separated and built to enable the circulation of heated water.
The shape of the section used for heating porcelain flasks full of sake is generally rectangular, but the openings in the water reservoir in the upper section of the unit have round openings to facilitate the insertion of sake flasks for warming. The openings in the water reservoir were covered by lids to keep in the warmth and prevent ash from falling in.
Kandoko Copper Sake Warmer
The piece of equipment made of copper that uses a charcoal fire as a heat source to warm-up sake flasks is called a 'Kandoko.'
It differs from 'Doko' copper warmers that are placed over a brazier. It is a piece of commercial equipment for use in establishments selling alcohol, and has been in use since the Edo period. Modern day sake flask warmers have changed to using gas as the heat source and being made of rust resistant stainless steel. Doko' style warmers that are placed over a brazier are no longer main-stream, and 'Kandoko' copper sake warmers are often simply referred to as 'Doko' copper warmers. Sake warming machines that heat the sake before it is poured into the flasks have become common, but actual 'Kandoko' copper sake warmers are built completely differently. Therefore, it is wrong to call these sake warming machines 'Kandoko' (or 'Doko').