Yohen 窯変

Yohen is a technical word of ceramic manufacturing.

Above two were made by Kuroki Fumihito and I presume he had used the same glaze. But they look different in colours… WHY?

(Some of you might point out why I said ‘I presume’ but don’t be fussy you will know the reason soon!)

Yohen is what makes them different.

So what is Yohen?

Yohen is sometimes translated as ‘accidental colouring’ because it is caused by a condition created naturally in a kiln by fire, temperature and ash from firewoods.

Let’s have a look at the lovely vases again.

The left one has got a bright blue while the right has yellow and a slight blue and looks darker overall. Iron in glaze normally makes blue colour when chemically reacted with less oxygen in a kiln. But it turns yellow when there is plenty of oxygen.

Potters use copper glaze to make green colour and there should be plenty of oxygen in a kiln. It turns red when there is less oxygen.

What’s interesting and exciting is no one can predict what’s going to happen after putting a fire in the wood-fed kiln filled with ceramic pieces. They stay up and take turn to keep the fire going for 36 hours in the private kiln and 55 hours in the communal kiln as the communal kiln is bigger than the private one. No one can control the fire in the kiln and the potters describe that the fire is a dragon.

Yohen brings more varieties, sometimes miracle and sometimes nightmare. That’s why each piece is so special.

The communal kiln in Onta Village.