Gas Firing 2016.02.20 Comments and Notes

This firing of the kiln went too long, resulting in Orton cone 11 flat.  Ideally, it would be cone 11 touching, then sagging a bit.

Upon unloading the kiln this morning, one thing was immediately apparent: the right side was far more reduced than the left. Yellower glazes and more slumping. Even on the left side there was some slumping, because of the excessive temp., and because of the clay which contained some low temp high iron clay to help seal the ware against leakage.

Left side, sagging only slightly, white surface.
Left side, sagging only slightly, white surface.
Right side sagging badly, white glaze turned yellow.
Right side sagging badly, white glaze turned yellow.

Chosen Karatsu came out pretty good, but the white was on too heavy, running down the pots too much.  It still came out looking ok because of the clay.

Most of the teabowls warped or sagged, so I only get to keep 2 or 3 of the 15. This is why teabowls are expensive, kids…IMG_3399 IMG_3398

All in all, not a bad firing, but need to adjust clay bodies, and pay closer attention to cones. Also, figure out the over reduction on the right side. It might be that one burner that sounds a bit off.

Kakewake CG bowls
Kakewake CG bowls
guinomi, need more sand in the clay
guinomi, need more sand in the clay
crystals, only grew on the right side, where reduction was strongest.
crystals, only grew on the right side, where reduction was strongest.
cylindrical tea bowls
cylindrical tea bowls
yunomi
yunomi
shells on feet
shells on feet

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saggared and much improved.
saggared and much improved.
porcelain, saggared
porcelain, saggared

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Fall 2015

has been busy.

I’ve gotten pretty far behind keeping up with the blog, falling into the bad habit of making small posts to Facebook. One of my areas of increased effort over the next year will be to work more on maintaining the blog, and getting it more integrated with other forms of social media. Trying to keep track of them all is like trying to herd cats.
I had made one promise to show before/after pictures for a couple of pieces, the first of which is the slab/paddle built sake chiller w/ feet and lugs:

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raw unglazed
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Fired piece, Chosen Karatsu style glaze. Matchbook for scale.
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Underside detail. Fired on shells, feet not touching the shelf.
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Glaze detail

 

The other thing I’ve been working on since early this year is getting a usable kohiki/clear glaze combination, because for some reason a lot of customers have been requesting white work. They have also been requesting black, so I’ve been working on getting a reliable semi matte black glaze. Mission not quite accomplished, but I feel I’m most of the way there. Here is the kohiki I’ve come up with and I am happy with it:

Kohiki cups. Cup on the left is unused. Middle has been used a bit, and right has been used a lot. The patina is beautiful in my opinion, and the fineness of the crackle is something I’ve been wanting for a long time in my work.
Various guinomi from 2015, mostly from the fall firing. Guinomi make great gyokuro drinking cups.
Various guinomi from 2015, mostly from the fall firing. Guinomi make great gyokuro drinking cups.
Seabirds on white.
Seabirds on white.
The other thing I have started doing is Japanese kana inspired brushwork
The other thing I have started doing is Japanese kana inspired brushwork, except with English. This cup is decorated with vertical English writing, a Goethe quote I like: “Whatever you can do, or think you can, begin it. Boldness has genius, power, and magic in it.” One of the other said: “Don’t be a dick.” These were more popular than I had anticipated and are currently sold out. Definitely making more!

Here are some of the pieces with the new black glaze. It seems to look best thin, and as with most glazes looks nicer over interesting wild clays rather than processed clays.

Type 1 semi matte black Katakuchi with black lacquer repairs.
Type 1 semi matte black Katakuchi with black lacquer repairs.
Type 1 semi matte black dish.
Type 1 semi matte black dish.
Semi mmatte type 2: two black glazes layered
matte type 2: two black glazes layered, makes a fatter glaze surface.

Chosen Karatsu Slabs

I had to make a batch of slab plates after the fall wood kiln firing, because every one of my slabs cracked in that firing. Turns out the clay I used was high in silica, and didn’t agree with the long wood kiln firing. The silica turned into cristabolite, and all pots made with that clay experienced shivering, or cracking, no matter what glaze they were paired with, and across a range of temperatures.

Forward a few weeks, and I’m frantically trying to get some replacement plates fired because this weekend is the fall open studio event, followed by an exhibition in Nagasaki during the first week of Dec.

For the most part this firing went well, aside from the fact that I exploded my large platter. Drat.

Red Lungs

Getting ready to set up a whole kiln load of glaze tests to fix my misbehaving ame (iron/ash) glaze, and realize that I’m out one very important ingredient, red ochre collected from a place right here in Taku. Completely forgot that I had used the last of it in my last glaze batch mixed up a couple months ago. Doh!

So…. Delay the mixing of test glazes for tiles and cups, I had to spend the day crushing and sieving red ochre. I haven’t used my man powered stamp mill in a while, and I added too much material to the mortar. My wooden pestle (4 foot long pole) that I use to stamp the material was just not up to the task because it was too light to sink down into the material and get it circulating in the mortar.  To remedy this, I retrofitted one of my wooden pestles with some  3cm diameter round steel bar left over from a long piece of bar I cut into sections for my kiln’s grate bars.

This new pestle worked really great, so great in fact, that material was flying out of the mortar from the striking force. So I proceeded to cut down a large cardboard box to keep most of that stuff from flying out or away. It is really hard work digging it, carting it around, and crushing it, I hate to lose any at all.

So anyway, here are some pictures of today’s festivities, and I did wear a dust mask, so I don’t have to worry about getting red lungs…

Mortar full of material, big chunks.
Mortar full of material, big chunks.

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My two 'pestles'
My two ‘pestles’
retrofitting with steel bars
retrofitting with steel bars
Now we're in business!
Now we’re in business!
Things moving along nicely now.
Things moving along nicely now.
Sieving. This is one of the jobs I dislike the most.
Sieving. This is one of the jobs I dislike the most.
This bucketful is sieved through 50 mesh. Before using it, I will re-sieve through 80 mesh, most likely.
This bucketful is sieved through 50 mesh. Before using it, I will re-sieve through 80 mesh, most likely.

And so it begins…

Two years ago, my supply of stable dobai 土灰 dried up. I bought up the remaining stock from the supplier, but that didn’t last long. When I switched to another source of dobai, the results were far different than what I had imagined. My two main bread and butter glazes haven’t been the same since.

Which brings me to my current predicament of having to basically start from zero and re-formulate these glazes with different ash. Fortunately, I have basic analysis info from the old ash, and also for the new types I will be testing with, so I can use glaze calculation software to calculate substitutions, which I am hoping will give me a head start.

For your daily dose of trivia, the word dobai is rendered in kanji as tsuchi 土, and hai 灰, or  ‘dirt ash’ (which makes no sense to me). All other ash has a proper name, like pine ash, oak ash, fern ash, etc… I finally found a possible explanation for this odd name the other day when I was searching for ash sources on the net. Turns out the ‘do’ of dobai is actually shortened from the original name ‘kamado’, which is a large pot used for roasting, cooking, burning stuff, etc. It is easier to say dobai, than kamadobai, after all, I guess…

Here are my 3 main candidates for testing:

WD_7EA2I picked up one kg of each, and will narrow it down to just one. They are all about 10 dollars/kg, expensive right?  I make my own pine ash because I have a good source of already burned pine, but I’m not set up to process large amounts of ash, and when it is all said and done, spending 10 dollars or more per kg is cheaper than the time and sweat put into making my own ash. Rice straw ash is more expensive at almost 20 dollars per kg and it is still worth it when you take into consideration the gathering, burning, quenching, floating, stamp milling, 2nd floating, (ball milling in some cases), and drying process this ash requires.

Chawan for Japanese Tea Ceremony

I am making the distinction, because this last trip to Korea and the tea bowl festival really accented the differences between the preferred shape of a tea bowl between cultures.

The one type of bowl here that probably illustrates the point best, but of which I don’t have a good example, are the Ido chawan. We make these forms in Karatsu, but don’t refer to them as Ido Chawan. Rather, we call them Karatsu Ido, or Ido Gata Chawan. The original Ido Chawan are from Korea, and contrary to the idea that the ideal shape is like Kizaemon (below), Ido come in many shapes and sizes. I’ve even seen on Ido bowl with a warikodai (foot carved into sections).

Kizaemon Ido
Kizaemon Ido
Karatsu Ido, Nakazato Shigetoshi
Karatsu Ido, Nakazato Shigetoshi

Anyway, if you look carefully at Ido forms, two things are often noticed: One, the lip is quite sharp on the inside edge, even though the outside of the edge is rounded, and two, the interior of the bowl is not rounded but rather pointed. These characteristics seem unrelated or even impractical for tea, after all, who wants a lip that is less durable, wouldn’t a round lip be more practical? Also, a cone shaped pointed interior is not suitable for whisking tea, is it? There is no room for the whisk to move, after all.

So why did tea masters choose these bowls as paragons of ‘teabowlness’?  The answer is simple. They weren’t used for whisked tea. Most tea practice revolves around usucha, or whisked thin tea, but the tea that holds the highest position in tea ceremony as an indispensible part of Chaji,  the full tea ceremony, is koicha, or thick tea. Thick tea is not whisked, it is kneaded and folded slowly into a thick paste with the whisk, and the coned interior of the bowl allows for this to happen much better than a flat or rounded interior. Then when drinking this thick paste, it is much better to have a sharp interior lip in order have a clean separation from the bowl when drinking. Koicha is usually a shared bowl, and will be shared by two or more people. After drinking, you must wipe the lip and pass it along to the next person. The sharper interior lip makes both drinking and wiping an easier less messy experience. So, these two characteristics end up being optimal for tea, in the proper context of Japanese koicha.

Even more interestingly, these two characteristics were not intentionally designed by the makers with koicha in mind. They are the direct result of the clay, process, and tools used to make the bowls, which were likely made quickly in large numbers.

In Karatsu, we use cows tongue ribs to shape the clay, because it is large particle material and not very plastic. In some cases, such as porcelain stone and sandstone, it is not even clay at all. The cows tongue allows shaping by compressing the clay body, rather than stretching, like a standard rib would do. I always thought that cows tongue ribs came from Korea, but I have never seen one there during my visits. There is, however, a tool that looks a little like a mini tugboat that functions much the same way as a cows tongue. When making bowls quickly with as little wasted movement as possible, the interior of the bowl naturally becomes conical rather than rounded, and pressing the lip between finger and cows tongue naturally produces the characteristic Ido lip shape, while preventing splitting of the lip by compressing the  un-plastic clay body, and also eliminates the need to use a chamois on the lip to compress or clean up.

So, I seem to have gotten off on a bit of a tangent here, but back to the  main goal of simply leaving you with some images of tea bowls:

 

E Karatsu chawan, Mike Martino
E Karatsu chawan, Mike Martino




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Chosen Karatsu Tsutsu Chawan, Mike Martino
Chosen Karatsu Tsutsu Chawan, Mike Martino

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Kawakujira Chawan, Mike Martino
Kawakujira Chawan, Mike Martino

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Kawakujira Chawan, Mike Martino
Kawakujira Chawan, Mike Martino

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Chosen Karatsu Chawan, Mike Martino
Chosen Karatsu Chawan, Mike Martino

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Chosen Karatsu Yohen Chawan, Mike Martino
Chosen Karatsu Yohen Chawan, Mike Martino

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Kuro Karatsu Chawan, Mike Martino
Kuro Karatsu Chawan, Mike Martino

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Chosen Karatsu Katakuchi Chawan, Mike Martino
Chosen Karatsu Katakuchi Chawan, Mike Martino

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