Tag Archives: wood fired

Processing Clay and Ash

In a recent massive cleaning around and in the studio, I changed things around to utilize some of the outside space more efficiently. One of the most important things is that I now, again, have a setup for processing clay and ash that I have collected and burned.

I had been getting close to finishing off my stores of collected clay that I processed some years back, time to start doing it again. I think I have a better system this time, and I have an inexhaustible supply of pine ash for now, too.

I have buckets, bags, and jars full of old collected clay and dry trimmings that need recycling. It should take some months to get it all blunged and pugged.

Collected clay that has literally been sitting around for years.
Collected clay that has literally been sitting around for years.

The Choppage ‘cho’ ‘pah’ gay’, is a traditional Korean tool for scooping off clay and other materials without disturbing everything underneath. It works much better than a ladle. I couldn’t find anyone who made them anymore, but my mentor still had one which is kindly letting me borrow.

Clay washing bucket setup, and scooping tool, called choppage.
Clay washing bucket setup, and scooping tool, called choppage.

I just agitate the material in the bottom bucket, wait, and scoop off the stuff that settles last.
Then, later after it settles in the upper bucket, I siphon the water back down into the main bucket. When enough of the upper bucket fills with material, I dump it into cloth lined basket or plaster to get out the excess water.

After returning water back into the main bucket from the 'good stuff' bucket.
After returning water back into the main bucket from the ‘good stuff’ bucket.

With the ash, the process is the same, but after I get out the good fine ash I transfer it into another bucket and wash it some more to get out the nasties. The nasties cause problems with glazing sometimes and I don’t like them. I do save the water containing the nasties for other uses.

Pine ash bucket setup, main on bottom, fine up top.
Pine ash bucket setup, main on bottom, fine up top.

The leftover rough ash stuff seems like a waste to just throw away, so I am thinking about ball milling it to see if it can be useful in some other way. We’ll see…

The leftovers after the good stuff is scooped off.
The leftovers after the good stuff is scooped off.


Scooping with the choppage tool.
Scooping with the choppage tool.

The sieve is 120 mesh, because I lucked into a cheap recycled sieve. I would usually use 100 mesh, so it is not much of a difference.

Dumping through sieve which is sitting on the bucket mouth.
Dumping through sieve which is sitting on the bucket mouth.

Views of a repaired teabowl

This is the teabowl that fell into the firebox during the last firing and broke into about 12 pieces. After falling and breaking, the firing continued, and the larger shards warped a bit, making it hard to get the pieces to fit just right.

Everything went back together, but some of the spaces were 1mm wide or more, and a lot of filling was required. Not only that, but the edges of the larger pieces didn’t meet evenly, making a lot of uneven fill lines. I thought about grinding down the higher edges, but in the end decided against that, because the fill lines were already so wide in some places.

So, here is the finished piece, with the lacquer and gold brushed on over the fill lines. A pro could have made thinner, more even lines probably, but it was good practice for me. A few more days to dry completely, then it will be time to whip up some tea…











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.