Tag Archives: feldspar

Let them eat cake

Here is my latest pot porn for you: freshly stamp milled, slaked, and filter pressed cakes of Izumiyama porcelain. 150kg. 


Not for the faint of heart, Izumiyama is hard to work with. It is non plastic and likes to crack during drying, impossible for slab work, and deforms easily. And it costs more than twice as much as Amakusa porcelain from Kumamoto. Most porcelain artists in Arita and Imari switched to using Amakusa porcelain long ago because it’s much easier to work with, doesn’t crack, and fires whiter. 


BUT! The beauty of Izumiyama in the wood kiln is absolutely undeniable. It fires to a soft ivory white and blushes in very subtle shades of peach. The surface is deep and translucent and vitrifies as low as around 1230C. 

Tomorrow morning first thing, Peter the Pugger will be getting a major workout!

2016-03-20 Glaze tests 釉薬の実験

Fired with cones 6,7,8 on top and bottom shelves. Pyrometer at middle shelf, didn’t display over 1215C.
Hotter on bottom than top. By cone, looks like cone 9+ on the bottom, cone 9 at the middle, and cone 8+ at the top.

Reduction strong at top shelf, weaker at middle and bottom.

棚三段、上、中、下。 オートンコーン6,7,8 使用、上:下置。温度計は中に。焼成中の温度計は1215Cを超えずが、上は8番コーンは曲がって、ヘタレ。下は8番フラット。 実際の温度は下:9+、ちゅう:9、上:8+ とみていいでしょう。
上は還元効いているようだが、中:下は中性気味。

Unloading:

Bottom shelf, front. Mid shelf, rear left. Top shelf, rear right.
Bottom shelf, front. Mid shelf, rear left. Top shelf, rear right.
Top shelf
Top shelf
Mid shelf
Mid shelf
Bottom shelf
Bottom shelf
Bottom cones
Bottom cones
Top cones
Top cones

 

Clay : Ash Blends  (Lft, to Rt.:  Bott.,Mid.,Top)

Taku shiro 90 : Dobai 10
Taku shiro 90 : Dobai 10
Taku shiro 80 : Dobai 20
Taku shiro 80 : Dobai 20
Taku shiro 70 : Dobai 30
Taku shiro 70 : Dobai 30
Taku shiro 60 : Dobai 40
Taku shiro 60 : Dobai 40

 

Stone : Ash Blends    (Lft, to Rt.:  Bott.,Mid.,Top)

Sandstone 90 : Dobai 10
Sandstone 90 : Dobai 10
Sandstone 80 : Dobai 20
Sandstone 80 : Dobai 20
Sandstone 70 : Dobai 30
Sandstone 70 : Dobai 30
Sandstone 60 : Dobai 40
Sandstone 60 : Dobai 40

 

Clay : Ash total, plus 280g Shirakawa

Clay:Ash total +280g toseki
Clay:Ash total +280g toseki

 

Stone : Ash total, plus 280g Shirakawa

Stone:Ash total + 280g toseki
Stone:Ash total + 280g toseki

 

Everything dumped together: Stone:Clay:Ash:Shirakawa

Clay:Stone:Ash:Toseki total
Clay:Stone:Ash:Toseki total

 

Stone:Ash 70:30 from top shelf (cone 8+) in the sunlight:

Stone:Ash 70:30 @ cone 8 1/2
Stone:Ash 70:30 @ cone 8 1/2

IMG_3681

New Videos

I finally sat down and figured out how to use my video camera and software. For anyone who is interested, here are some videos I posted to youtube.

Karatsu Sake Cups

Sake Cup Trimming Part 1

Sake Cup Trimming Part 2

Karatsu Teabowls

Karatsu Teabowl Trimming

All of these pots were made with clay from the property, discovered right under where we built the kiln. It has a lot of iron, but still takes some heat, and won’t bloat at higher temps. Probably due in part to the fact that it is very open with a lot of sand and other even larger inclusions. Even vitrified, it still sweats because of the openness. With use, the sweating stops, as all the pores fill with minerals from the water and tea tannins, etc…

Sitting down at the wheel again

Lately I’ve been spending all my potting time making large stuff for the next firing. It takes forever to dry, and I need extra time to bisque it all. Yup, all of it. No more cracked pieces because I glazed them raw and effed up.

So I was at a big drinking party the other night. My neighborhood mens group gets together bi-monthly to catch up and eat good stuff. A good custom overall. Anyway, the guy who hosted the party turned out to be a sake enthusiast as well, and while everyone else was drinking shochu (a hideous drink fit only for odd, uncivilized folk…      just kidding….), he broke out a bottle of the local brewery’s best, and two very nice guinomi, one wide and shallow and one deep and tall. The hira-sakazuki (low, flat one) was a beautiful blackish red uber reduced surface, and made from really nice clay that contained quite a bit of iron, was fairly fine, and which was trimmed to perfection. The taller guinomi was Bizen Karatsu style, otherwise called yakishime. Neither were signed so I have no idea who made them.

hira-hai (hira sakazuki) and chawan
hira-hai (hira sakazuki) and chawan

The gorgeous hira-sakazuki inspired me to get back on the wheel and start making smaller work for the next firing. I started with hira-sakazuki and finished with Karatsu style tea bowls. It was nice to be back in the saddle, and the clay, which came out of the ground near my house, was beautiful to work with now that it has aged a few months since I processed and pugged it.

I ended up spending more time than I wanted on each of these, forcing myself to slow down the wheel and throw slowly, with as little motion as possible. I wanted these simple shapes to remain simple and not look too refined. One of the buzzwords for Karatsu ware is ‘Soboku’ 素朴, which roughly translates as ‘rustic’. Too much handling and you lose that quality. Spent all of that time processing local clay, it would be a shame to waste it by over-handling it.  All of these pots will get a thin to medium coat of 90%spar and 10%ash. Maybe a couple of the sake cups will get a thin coat of iron and ash.

8th Wood Firing Photo Record

This post is a photo record with comments, in order to organize and retain my thoughts and observations about the 8th firing of the wood kiln. I always think I’ll remember until the next firing, but never do. So, if you get into this, beware there are a LOT of pictures, some of which may seem redundant. There are examples of most of the pots from the firing, minus teabowls and some others which are not photographed yet.

The 8th firing was a charm overall, with many good pots, some bad, and some that will get refired. Kiln was fired in oxidation primarily. We stoked once every 30 minutes for 2 1/2 days, then once every 20 minutes the last half day.

– Front was nicely melted, nice even gradient to the rear of first chamber, E-Karatsu was about ideal. Cone 12 at hottest front down to cone 6 at coolest rear.

– Front chamber behaves like anagama. No significant temp gradient from front to back of each setting. Next firing, will pack kiln by eliminating the space between settings, leaving horizontal space for flame travel. One long setting from front to back of first chamber.

– Ame yu better at low temps. Load rear to mid chamber.

– Ao yu needs more heat, mid to front chamber.

– Large platters go midway to back of front chamber. Too much ash up front.

– Firebox wares are very nice in a three day firing. Great place for Shino, under cover to avoid ash in pots.

– Rear chamber fires fast when preheated for 3 days. Jumped from 1044C to 1344C in four stokes, a little over an hour. Care must be taken to spend more time soaking at high temp, because rear chamber high temp wares not quite mature (surface changes only), clay not melted well. Spend 3 or 4 hours firing off rear chamber, slowly, to get inside the pots.

– Rear chamber fires very evenly front to back, and top to bottom. Pick a temp to fire at and load accordingly. Don’t expect a significant gradient.

 

A Mining Trip

Today, in spite of the typhoon passing by us, 3 of us potters decided to go out to a construction site that we previously scouted, and collect some great feldspathic sand. The whole mountainside is sandstone and the construction process has done a good job of crushing great amounts of the stuff, with trucks, back hoes, tractors, and the like. Then, when it rains, the fines travel down the hill and collect in the gutters and sumps making it easy to collect lots of fine sand which does  not need to be processed further in the stamp mill.

Today everything was damp, so pretty heavy, but having cloud cover was great and we hardly broke a sweat. Sunny days here in the summer can be quite unbearable.  We got at total of 38 bags of sand, and I brought home about 600kg.

Now that the mountain has been worked over pretty good by the construction company, places to collect sand have decreased, and the whitest sand (less iron contamination) is no longer available. We did get about 7 bags of the white stuff, with the rest more reddish/brown. I also found one nodule of iron (called ‘oni-ita’) in a sandstone boulder and dug it out to make underglaze pigment with.

This sand is great for adding to your clay, really gives it some character and helps it to mature at a lower temp, while preventing slumping. You can mix in up to 50% or more sand into the clay depending on what you are making, and the finest of the sand can be wedged up all by itself and made into smaller guinomi and chawan sized items.