Tag Archives: karatsu

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.

WD_1020

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.

Crazy stuff

Lately I’ve been working on ways to bring out the crackle in my teabowls, as well as make the crackle finer (without having  to use them for decades or centuries, or reformulate my glazes,  so in other words: cheat).

These two bowls had big crackle ( 1cm +-) and I reheated them, then doused in cold water.

***WARNING: Ceramics generally don’t like to be heated or cooled quickly. Don’t do this if you’re going to be upset about breaking a bowl!***

For the kohiki bowl, I heated and doused once to make the crackle smaller, then reheated to open the crackle wider, and closed the damper on my stove, to get that carbon to penetrate the crackle.

Because the body and the glaze were vitrified, but the white slip in between wasn’t, spots (where the slip was thickest) on the rim separated from the body and had to be restored with lacquer and gold (*1)

The results vary, and it is high risk, but you can get an idea about how your bowl may mature over years of use, and plus it’s just fun to play around with fire…

Another common way to bring out the crackle in you ware is to boil it in a pot of strong tea for a few minutes. The tannins will then turn brown, especially if you put the piece out in the sun to dry (or any other UV light). For an even darker, quicker reaction, after the piece is dry, apply some iron acetate. The iron acetate reacts with the tannins and turns quite black over a period of 24 to 48 hours. This is actually an old woodworking technique that I applied to pottery, and it works well, in addition to being non toxic.

***Results may vary***

(*1: I didn’t use real gold for this bowl, but I would on a very nice piece. For this piece I used a brass based metal powder. For more info on this kind of repair, check out Dave Pike’s blog, or store on Etsy)

 

 

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.

Pieces and notes fall firing 2014

Fall 2014 Wood Firing Continued

The unloaded pots have now been hammered, moved inside the studio, or are getting refired. The ones that have been moved inside the studio are starting to get cleaned up and polished, in preparation for next spring’s shows.

All in all, there were some 750+- pots in this load. I’m not sure of an exact number because I started smashing before I had a count.

Here are some of the pots that I started cleaning up today. Most of them are small  dishes, ranging from 10 – 17cm across.  All sizes listed are width, and are approximate measurements.

2014 Fall Firing: Unloading the Kiln

Here are images from Saturday’s unloading of the kiln.  Some good, some bad, but mostly good.

Most problems came from mistakes made with clay or glazes, the firing of the kiln was exactly how I planned… first time ever.

Got a nice gradient from about cone 12-13 in front, to cone 6-7 in the back of the first chamber, and an overall cone 6-7 in the rear chamber.

Biggest problem was crawling of iron brushwork on raw ware. I will touch up bare spots and refire these.

Lost both big slabs, which both cracked BADLY.

Madara  and E-Madara items came out really nice overall, with lots of subtle blues.