Category Archives: tools

Firing for anyone

In Japan, people often visit pottery studios for a short pottery experience, either painting something or making something small to be glazed and fired later by the studio owner or a craftsman. This has always seemed so limited to me, and the inevitable comment, “Oh, you are so lucky, I wish I could do this every day!” always prompts my response: “Yes, me too!”. Most people just don’t have any idea what goes into a finished pot. Turning it on the wheel is maybe 10% of the overall process, much less if you gather materials yourself and/or wood fire  your work. And customers rarely see the failures, or all the polishing that goes into a piece and assume the potter just opens  the kiln door to a batch of warm, super looking, ready to sell pots.

Finding a way for people to experience more of pottery making is a challenge, because of the time it takes drying, bisqueing, firing, and waiting to cool down. Raku firing abbreviates this a lot, but still requires a lot of specialized equipment in most cases. Shichirin fired pottery, for me, is a good way for anyone to have a firing experience, including the excitement of the fire, the engagement with the work, the post fire polishing and critiquing, and even the failures and serendipitous successes.

Lately I’ve been working on a firing method that is accessible to everyone, with items available at most home centers. I got this idea years ago when a Japanese potter named Yoshida (don’t remember his first name) made a splash by introducing “Shichirin Togei”, which used a  small Japanese BBQ, called a shichirin, to fire small objects. This developed into a book called Minigama, which I never read, but outlines the construction of small handbuilt kilns from fireclay and fired with wood, charcoal, and forced air. I think the book is out of print now.

I liked the idea of shichirin togei, but thought the open shichirin was maybe not so efficient at getting up to temp, so I added another one on top, like a clamshell, with both shichirin wadded together with a coil of clay. The bottom damper is the air port, and the top damper is the chimney opening and stoke hole.

You start by packing some charcoal into the bottom of the chamber, around a stilt on which the pot will sit. Then place the pot on the stilt and continue covering with charcoal. Then place a coil of soft clay around the mouth of the shichirin, and overturn the second shichirin over it.

Now that that is done, time for the fun to start! Use a hand torch to light charcoal, then use a hair dryer to get things burning hot.

Now just wait for things to heat up, it will take a few minutes, after which flames will start to emerge from the top damper hole.

This flame should continue to grow and get jumpy, making noise as unburnt gases from inside the chamber exit and combust when they meet more oxygen.  Keep slowly adding pieces of charcoal from the top stoke hole (damper), keep that flame extended. As it gets nice and hot, you’ll be able to tell how the kiln breathes every time you put in a piece of charcoal, and you’ll get a sense of when to stoke.

The first firing might take about 45 minutes, because of the time to heat everything up. From the second firing, 30 minutes seems to be enough to fire the clay. If you have time, you can go longer, and ash from the charcoal will leave more green ‘glaze’ on the surface of the pot.

…a new floor!

(You have to read the title in your inner Bob Barker voice for the desired effect)

I had a pile of planks laying around that I’d received for free and intended to burn in the kiln, but they turned out to be covered in mud and I didn’t want to clean each one by hand just to toss them in the fire. 

They are nice thick pine planks, and I had this sudden inspiration to make a raised floor for the new studio storage area. It was a very good feeling to have a pile of trash disappear as a new floor emerged! Quick, easy, and free. How often does that happen?


I still have shorter pieces left, and will use them to fill in the still open triangle on the right side. 

Fall firing 2016

Open comments and notes

Front came out beautifully, mid stack as well, rear a little cool. Very top of front, mid, and rear were cold. Shelf config caused this, I think, because of the large shelves being close together, creating strata in the heat gradient. The very front shelf with guinomi and chawan was the main culprit, blocking the flame from rising, and directing it under the large shelves placed midway up the front stack. 

In the future I need to stagger the shelf levels during stacking, to allow the flame to travel upward.  Also, block some of the floor level flue channels at the rear of the chamber. Make sure upper flues are fully open. 

Front cones are 9, 10, 11, 12 Orton. 



Fall Open Studio

Just a short post of some pictures from the studio sale this weekend.

Coil and paddle

I have been working on coil and paddle pots these last few days. This is a sequence of photos from a jar I made today. It’s not very big, probably about 36 cm across.


  
  
  
  
  

My favorite studio tool…

….is without a doubt the Peter Pugger de-airing pugger/mixer. Until two years ago I did all of my clay and stone mixing in a large deep platter by hand, and it was killing my wrists.  Hearing all the wonderful things Peter Pugger had to say on their website, I took the plunge and decided to spend the money and save my hands. I figured if the thing worked half as well as it was supposed to, I would be ok.

Well, it is now about 2 years since I got it and it does everything it is reputed to do, and does it very well. My wrists are now pain free, and I have saved hundreds of hours of time processing and blending clay bodies.

Blending wet clay bodies usually takes about 15 minutes of mixing, but mostly I mix dry materials with water (sometimes blending into wet bodies), and this takes a while longer, usually around 30 minutes.

In my work, keeping the character of the wild clay is of utmost importance, and I’ve found that de-airing generally kills that character dead. However, the de-airing is necessary in getting the water to penetrate the dry materials more quickly, so that I don’t have to let the pugged clay sit for a month before using.

My solution to this is to let the clay mix, then I de-air it once completely, followed by re-mixing the batch for 5 – 10 minutes after reintroducing air. This gives me clay that is not as easy to throw, but which gives very nice trimmed texture.

Here are some pictures of some clay from the other day which I collected from the mountain behind my home. I added the dry/damp clumps of clay to the hopper (removing as many large rocks as I could find), then water, then mixed. I repeated these three steps until the hopper was full, then mixed for about 20 minutes, turned on the vacuum pump, and de-aired completely.

Next I went to lunch.  It was yummy. It was sunny on the deck and there was a cool breeze. The neighbors have a  great cherry tree in full bloom and the wind was blowing the petals off, and they were fluttering across the yard like giant pink snowflakes. I noticed as I saw some of them fall across the deck that the wisteria was budding out and even starting to show some purple. Nice. I imagine the wisteria will be in full bloom a few weeks early this year.

After coming back to the studio, I re-introduced air to the mixing chamber and mixed some more, then pugged it all out and made some pots. The whole process took about 2 hours. It takes even less time if you decide not to include lunch, but I recommend including it.