Monday, April 12, 2010
Firing the Noborigama
Saturday April 10th at 4am the Tamayaki (also known as noborigama) was fired up, making it the first one of 2010 at Sara Yama Studio.
The noborigama's fire is fed from 4am to 10pm, so a total of 16 hours of manual labor and temperature monitoring is needed. Sara Yama has about 50 students including myself from around the area. Each person is required to do a 3 hour shift to help with the noborigama.
To understand the workings of the noborigama I'll go through its stages.
From 4am the fire is lit and fed a constant supply of wood. At this point the type of wood does not matter, usually Arai Sensei has old boards or junk pieces from wood shops near by who donate old scraps they don't want to dispose of. (Of course the wood has to be pure, no paints or nails in them)
The temperature of the kiln has to rise steadily, rising too fast or too slow means the pieces will not turn out correctly. So feeding the fire the right amount of wood is tricky. Luckily modern technology has a helping hand in making sure we do it right. In the picture on the left you'll see a beige box, this little machine monitors the temperature of the 2nd and 4th dome of the noborigama (remember the noborigama has 4 domes) This machine is attached to the noborigama with two wires that have temperature readers at their ends, the readers are located at the top of each dome. This is the only technology used in the process, the rest is all done by hand, no machines or gadgets.
The temperature should rise 100 degrees Celsius per hour (50C per half hour) The temperature is recorded every 30 minutes in the Sara Yama's noborigama log book.
Going back to the schedule...like I mentioned before, from 4am the fire is started, the wood is fed into the base dome from the front. (See picture on the left.) From 2pm (after 10 hours has passed) the temperature is at 1000C. See the iron door on the right side of the kiln front? This door is now shut after reaching 1000C and wood is no longer fed through the front.
But a few hours before (11am) the front iron door is closed, we move to the side of the 2nd dome. If you remember from my previous post, this is the door where the pieces were handed to Arai Sensei one by one to be stacked in the noborigama. Since then bricks have been put in the door. (Of course before the fire was started at 4am) Since the door is an odd shape the bricks are of all different shapes and sizes and of course numbered so they can be put back in the correct order. Look at the picture of the door, you can see the numbered bricks. Can you find number 27? It's towards the bottom left hand side, it has an indent on it. Remember this brick for later on.
Retracing our steps, the iron door has been sealed and we've moved to the door on the 2nd dome. As you can see between the bricks there are cracks, letting heat seep through, for the remaining firing process we do not want heat seeping through. So a mixture of just regular old sand and water is made, it's a gooey consistency, good for slapping on wet bricks.
Before slopping on the sand mixture the bricks are prepared by wetting them with water. At Sara Yama an old broom and bucket of water do the job quite nicely.
Using gloves, the sand mixtures is pressed into the bricks. There's no right or wrong technique to this, just as long as the cracks are sealed sufficiently all is well. It's super messy but nothing goes to waste, the sand that falls is picked up again with a shovel and pushed back into the bricks until it sticks. Now that the door is sealed, it is let to dry and wood is fed into the front until 2pm.
Now from 2pm, things change drastically and it gets more complicated. With the side door dry and the front iron door shut it is time to proceed to the most important step. Remember brick 27? Well it is special since its removable, it is now the only hole to put fire wood into the noborigama. (See picture on left, you can see the roaring fire inside through the small hole)
No more scrap wood, now pine is fed into the fire. You can see the small wood cuts of pine here, they're the perfect size to fit through brick 27's hole. This entire pile of wood will be fed into the noborigama from 2pm until the end, 10pm. (total of 8 hours)
Putting the pine wood into the side is a 3 person job and is very labor intensive. There is a technique to this, three sets of 15 logs are thrown into the noborigama at a time, at intervals of about 15 minutes. The middle person has the easiest job, so beginners are usually in the middle since all they have to do is pass the logs between the first and third person. The first person passes the logs from the pile to the second person and they count the logs out loud to make sure the correct amount is inserted. Second person passes to the third person. The third person has the toughest job, also while counting the logs they throw them into the fire through the tiny hole, but there's also a technique to this as well. The first set of 15 logs has to be thrown quite far into the kiln so the angle in which the logs are tossed in has to be perfect otherwise they pile up and never reach the other side of the noborigama. If this happens the fire is uneven inside which means the firing process could be ruined if it keeps happening. The second set of 15 logs goes into the center of the noborigama, and also needs to be thrown at a certain angle to reach the right spot. The third set of logs is the easiest to throw since it's the closest to the hole and doesn't need much power.
This may sound simple but the entire process happens in a flash. Imagine throwing 45 logs into a hole the size of your hand, while counting them and aiming them at the right spot in less than a minute. I tried the first persons position and messed up terribly the first time. The logs piled up at the hole and I just ended up embarrassing myself more so than helping. It takes a lot of practice and power. The men mostly do this job, but they welcomed me to try and encouraged me to keep trying again. Eventually I'll get the hang of it.
After the pine is added, the smoke from the noborigama turns black, as you can see to the left. After 8 hours of feeding 45 logs into the kiln every 15 minutes brick 27 is sealed with the sand mixture and the noborigama is left to sit for one week to cool down.
Sunday, April 18th we will open the noborigama and see how all of our pieces turned out. I'm so excited! I hope the 18 pieces I put in are still intact!
**Picture is me and my pottery friends! Come visit us at Sara Yama!