Friday, March 10, 2017

Holes, holes, holes … micro to huge: Charcoal cooking in Niiharu Citizen Forest

Bincho charcoal 備長炭 is made by professionals for continuous 2 weeks. Unless we have a high-tech kiln, Niiharu Lovers, i.e., weekend citizen volunteers, cannot do this obviously. Having said that, even if Niiharu’s charcoal cooking is a one-day task, I understood it was a LONG activity. How long? According to my senior volunteers, it was about 8 or so hours’ activity so that when we began cooking at 6:00 in the morning, the task would be completed at 14:00 … well, it was an estimate when the kiln was (at least) not old. I joined the charcoal making this winter. It took 14 hours … and we figured it out why when we opened the lids 3 weeks later. Before going to this point, I tell you my adventure on that charcoal cooking day.

So, it takes time to make charcoal. Starting a day earlier, the better. It is a kind of tradition for Lovers to fire up the charcoal kilns at 6:00 in the morning. Luckily, it was a very fine day. The air in Ikebuch Open Space was clear and crisp. Wonderful! Basically, as we have to operate kilns for hours, firewood for charcoal making should be able to keep fire long. I didn’t know firewood made of coniferous trees were not good in this regard. “…Look for woods dry enough ... You know, fallen branches of cedar or cypress are good for starting fire since they can burn very quickly. But to maintain the firepower continuously, it’s tricky to use their logs. Firewood from Quercus family, like Quercus acutissima and Quercus serrata is far better …” One of the senior Lovers told me when we gathered firewood from a shed in Ikebuch Open Space. Hmmmmmmm … so, the artificial forests made of coniferous trees are really for urban development, I surmise. The broad-leaved forests for coppicing had a very good raison d'être when people depended on mountains for energy ...

Needless to say, it took a while for inside of kilns to be heated up. Making and maintaining the flow of hot air is the key. It translates into the position we burn the firewood. “Keep the fire at the mouth of the gutter, and make large enough space at the end. The end of the U-gutter is under the hole of the drum. Let the hot air created at the mouth flow to the end and go up through the stove pipes. The air will steam the bamboos inside.” I realized it was a matter of will when we guard the fire. It’s so tempting to add more firewood hoping the fire deep in the gutter may grow bigger. Wrong. When we stuffed the furnace with logs, the end of the gutter was deprived of oxygen. The fire there could be extinguished even if the flame was large at the mouth. The air did not flow smoothly to the drums, and cooking would not go well. Patience was needed, in addition to adjust the fire-force at the mouth. Really, PATIENCE!

Fuzzy, fuzzy …
I was sleepy then.
Firewood of Quercus acutissima
The pipe from the lid is holding
the end of industrial thermostat
to measure the temperature inside.
Being a part of industrial regions of Japan,
Kanagawa Prefecture has
leading manufacturers of industrial thermostat.
One senior member of Lovers has
a very good connection with them
to procure such tools at reasonable price.
Whatever, it takes time for the inside to get hotter …
You may notice the difference between the two kilns
… That’s the problem. More to it below …

The seniors told me the temperature inside goes up exponentially. The slope of the curve depends on the amount of moisture the material contains. The thinner the bamboo wall is, the quicker it heats up. At the beginning of cooking, bamboos release steam with the heat from firewood, and hence the gas comes out of the bamboo funnels are mainly water vapor. Comparing with woods, bamboos are constructed of far larger number of micropores that contain H2O. That’s why we often encounter bamboos vigorous enough to ooze out droplets from a cut end. When we cook charcoal from bamboos, chimney of a kiln would emit lots of white smoke that is mainly water steam. Sure enough, eventually, the bamboo chimneys of Niiharu kilns started to spew out white smokes. Or, observing the reaction of my seniors, it seems to me checking out how fast the white smoke comes out is the first target of operation. “Hurrah! The white smoke comes!”

The bamboo chimneys from the kilns
gushed out white vapor.

It also means we have to be ready to collect wood vinegar. Bamboos contain acetic acid which made them good material as insect repellent for the base of mud walls in traditional Japanese houses. The acid is vaporized during charcoal making and released through the conduits from a charcoal kiln. With cold winter atmosphere the vapor containing H2O and acetic acid from the drum rapidly cooled and dripped in the bamboo buckets situated at the mouth of metal pipes. At the beginning the collected liquid was more of water, but gradually it was tinted darker and darker in amber. I licked little bit of them from time to time. The beginning, it tasted … er well, water. Then, it became more and more acidic. Accordingly, the color of smoke from the vents turned from white to bluish. The seniors told me when the smoke obtained purple, it’s the sign we should stop adding firewood. I was looking for that mysterious purple … Oh, by the way, till 100 or so years ago, wood vinegar was used by married Japanese ladies to tint their tooth black and to shampoo their tightly coiffured hair. (Please imagine Madam Butterfly in the Met or the Covent Garden.) At that time, tooth blackening was the social norm for married women, and coiffured long hair invited lots of lice. Wood vinegar was safe must-have to treat both issues. It would be a very good research topic for anthropology, “Evolution of Satoyama and Japanese power structure of gender”, wouldn’t it?

Bamboo vinegar drops in …

The liquid collected in this way inevitably holds soot. Niiharu Lovers sell charcoal and bamboo vinegar manufactured in this way at City festivals year-round to raise funds. In order to make the vinegar marketable, we have to strain it. Traditionally it’s done by “a bamboo funnel” in Niiharu. It goes like this …

The funnel,
a 1m bamboo log tied up straight
to a pillar of the charcoal hut
Inside the log is hollowed out,
except the very last section that has
a tiny 3mm hole opened by an awl.
And above the last section, the Lovers tightly stuff rags,
leaving the top for about 10cm.
There is an order to pack, a sort of.
The texture of fabric gets coarser to the bottom
so that the rag immediate above the 3mm hole is a mesh.
The top is a woolen fabric.
Here is a good logic.
The top of the funnel is to strain the soot,
and the materials removed get fewer
as the bamboo acid trickles down inside the funnel.
Stuffing the rags
The collected liquid is poured in the funnel,
and …
comes out about 20 minutes later as
“purely hand-made” bamboo acid.
We collect the strained liquid,
and repack them
in cleaned 500ml plastic bottles
for fund-raising.

So we watched the fire, collected the bamboo vinegar, cleaned the metal pipe coming from the drums from time to time, and … waited for the bamboos to be heated up in the kiln. In theory, when the inside temperature reaches more than 500°C, the smoke from the chimney becomes blue-purple, which is the sign the water is completely extracted from the wood. When we add more external heat after this point, the bamboos in the drum become ashes. We have to close the kiln completely ASAP to deny the oxygen inside. Nonetheless, for a while bamboos inside will keep on burning themselves to touch 700°C or so, with the heat it stored during our firing. After the max temperature, they gradually simmer down to the level of outer atmosphere. The charcoal cooking is the process until we blockade the kiln. (Bincho charcoal is made of a final fire-up after opening the blocked kiln, which is a skilled task of professionals.)

We were hopeful at this stage…
The pipe cleaning stick
Cleaning the vents during cooking
During the wait, we prepared for the next cooking day …
We also cleaned, trimmed, measured and packed
the products made in the previous operations for selling.
Ours is popular and easily sold out in City fairs.
Recently, the City Office asked the Niiharu Lovers
to keep on opening the marquees during any event
even when we sold out all the products we brought
from the charcoal kilns and the atelier for wood crafts.

Before, the Lovers could seal the furnace at around 14:00 … this time, er, no. At 14:00, inside of both kilns was still 200°C. The Lovers frantically added more firewood and cleaned the pipes, and waited, waited, waited … Meanwhile, cone-shaped Ikebuchi Open Space was filled with the bluish, but no-purple, smoke. Now I understood why the people of Hikarigaoka Housing Complex were in a rage to volunteers of Shikinomori Park. (er, of course, Lovers of Niiharu obtained the permission from the fire station to do this in the forest.) Woooooooow. The operation from the dawn reached to the dusk, and the kilns’ temperature was still less than 400°C. “Well, it’s strange.” “Why?” “Anyway, we have to keep on burning the firewood.” Eventually, we ran out of Quercus firewood. We were forced to burn the logs of coniferous trees. The forest entered into the night ... I could not see any purple smoke from the kilns in the end … I didn’t know either Yokohama’s sky could be that dark with lots of stars above us … beautiful hole in light polluted sky of Tokyo Megalopolis … come to think of it, that’s why no one came us to complain. No light pollution means none lives near from Ikebuchi Open Space.

I would say the smoke is … a kind of blue … isn’t it?
And we are still here …
So, let’s clean the vents …

The kilns finally arrived 500°C at around 19:00. We checked if the air from the pipe vents from the drum can ignite matches. They did! It’s a sort of ritual, whose practical meaning was to see the sign the smoke contents from the drums included very few water, if any, and hot enough for the bamboo sticks to self-steam to be charcoal. The Lovers then hurriedly made another butch of red cray paste, sealed the furnace with bricks and cray, and finally went home to bed. Phew. 3 weeks later, we opened the lids, and found nicely charcoaled bamboo sticks … surrounded by crumbling wall of drums. One of the drums actually had huge holes on the wall near the bottom. Ah-ha. That’s why we struggled to heat up inside.

Night playing with mud
Fire ignition!
Closing the furnace, hurriedly.
Otherwise, the fire would turn the bamboos into ashes.
We also removed the bamboo conduits
and covered tightly the mouth of pipes
from the drum with
aluminum foils and bamboo buckets.
The sealed-off was complete.
The change in temperature inside the kilns. The vertical axis measures the temperature.
The horizontal one is for hours. I won’t say they are not exponential, but …
3 weeks later. Digging out the kilns.
Opening the lid …
Voilà! Bamboo charcoals we made!
Our product
And one of the large holes we found

“Er, well, yes, the kilns are reaching to their limit.” “Hmmmmm … will we replace them with new drums?” “That’s the option we’ll think this summer, isn’t it?” For now, we have covered the holes with bits of metals, and operated the kilns two more times for this winter with lots of vent cleaning to reduce operation time. It has been shortened to 9 hours! … In any case, due to the porous structure of bamboo charcoal, they are ideal deodorant. We can use them almost permanently as such when we dry them with direct sun once in every 2 months for dry season, or in every month during rainy season. Caution: never wash them by chlorined tap water. The chemical remains the micropores of bamboo and block the space where the molecule of smelly staff comes in, i.e., destroys the ability of bamboo charcoal as deodorant. If you visit any City fair of Yokohama for environmental matters, Lovers of Niiharu would be there with our charcoal. Good to see you, and thank you for your donation!

If you find a problem in Niiharu Forest, please make a contact with

Office for the Park Greeneries in the North 北部公園緑地事務所
Yokohama Municipal Government Creative Environment Policy Bureau 横浜市環境創造局
Phone: 045-311-2016 (I guess in Japanese only)
FAX: 045-316-8420 (I hope there is somebody who can read English …)

Niiharu Administrative Office / Satoyama Exchange Center 新治管理事務所・里山交流センター
Phone: 045-931-4947
Fax: 045-937-0898

No comments:

Post a Comment