Tag Archives: wood kiln

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…

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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…

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.

 

Keeping track of clay

As I may have mentioned before, buying the pugger/mixer was probably the best decision I made last year. It has made my life easier in so many ways. However, it has made things more difficult in one way: it is hard to keep track of all the claybodies that go into the kiln. Especially after they are made into something and drying on the shelves, it is very difficult to tell them apart.

When I fired with the gas kiln, stuff didn’t pile up all that much, because I fired frequently. Now with the wood kiln getting fired 3 times per year, things tend to stack up, and labeling is essential to avoid hideous mishaps. I try to keep types of clay consistent from wareboard to wareboard and label each board, but packing pots in the kiln to bisque them means losing the labels and taking extensive notes, because bisqued clay looks even more similar than green.

The other day, I was wishing I had a way to label the pots better, then it came to me: a labeling app on my smart phone with which to label photos in my gallery. I downloaded a free app (there are lots of different ones), and viola!, pictures taken of my bisque load shelf levels are now accurately labeled and instantly backed up to my home network, so I know I won’t lose them.

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Now if significant time passes between firings, or just unloading a bisque, I can refer to my pictures to figure out what everything is.