Inkstones are used to turn solid blocks of ink into liquid ink.
A little water is poured into the inkstone then the ink stick rubbed against it, releasing an indescribably beautiful perfume that calms the mind and makes you want to sit up straight.
I used to think that this perfume was the smell of the ink itself, but in actual fact it is added while the ink is being made.
The glue that is used to bind the ink into a block has a distinctive smell of its own, and it was in order to disguise this that perfume was added.
All Japanese people will have experienced this perfume when they practiced calligraphy as children, but few realize that it is actually derived from incense.
The inkstone used to dissolve the ink - releasing a beautiful perfume in the process - can be made from pottery or old tiles, but by far the most common type are stone.
The best are known as Tankei-suzuri and are made from stone quarried in China.
Of course, an inkstone must be able to grind the ink consistently, but they are also graded according to their color and sheen, whether the hand seems to be sucked into it when it is touched, and the time it takes for the condensation to disappear when breathed on.