Tag Archives: clay

Images from WIT2014

Workshop in Taku, 2014. This is what you get when a professional photographer runs wild, and is kind enough to share. Thank you Robert (Brad) Haughie!

 

Bisque 素焼き

Today is the first load of bisque aimed at the fall firing of the wood kiln.  About 28 ware boards worth of pots, I really tried to get as much packed in as possible, to maximize the gas used.

I don’t pack glaze firings very tight because I want the calories getting around to  everything, but for bisque I’m not too picky.
700C – 750C is my usual peak temp,  I like the ware to be very absorbent for glazing, however the resulting ware is quite fragile and needs careful handling.

This time around there are quite a few slab plates of various shapes and sizes, which I am a bit worried will crack. These are stacked on spacers, then more spacers between stacked plates, because I don’t want to take any chances with cracking. The rest of everything is pretty safe, so packed and stacked without too much thought other than to get as much in as possible.

Clay/Centipede Storage

In 2010, when we started digging the trench for the wood kiln, we found a seam of clay from about 60cm – 90cm down. This 30cm thick seam stretched as far as we dug, but with varying levels of iron. I ended up keeping a few hundred kilos of the lightest stuff, and it has been taking up space in bags that have been slowly decomposing over the last 3 – 4 years.

Finally, I rallied the gumption to get that big pile of clay moved today. First, I built an enclosure on the edge of the property behind the kiln chimney, then I started shoveling. The bags were so far gone that they just tore apart if I moved them, so there ended up being very little heavy lifting.

Scavenged  roadside construction boards.
Scavenged roadside construction boards.

I recently came into a big load of boards used by roadside crews to build temporary retaining walls. They are nice sturdy pine boards (2 1/2 inches thick) and are great for all sorts of projects, although they are not all that great looking.

I ended up just pounding in some steel stakes and tying the boards to them. I looked for some little screw-in brackets to go around the rods and onto the wood, but alas this is Taku, and none of the hardware stores had that sort of hardware.  This happens often, and my go to solution is almost always the same: stainless steel wire. It is cheap, comes in various thicknesses, and pretty much lasts forever once in place.

Stainless steel ties.
Stainless steel ties.

Once two sides were finished, I had a place to put clay, but the storage area is not quite finished. I still plan to put in  one or two dividers, so that I have 2 or 3 sections for storing different types of clay. Here is what it looks like so far:

Clay settling into its new home.
Clay settling into its new home.
Clay from the kiln trench
Clay from the kiln trench
Clay from the neighborhood reservoir
Clay from the neighborhood reservoir

The clay that is still in bags came from about 200 meters away, from the farm reservoir. We drain and muck it out once every 2 years, and that is when I discovered the clay seam.  It is not very refractory clay, but it makes very nice pots if fired to the proper temp.

During the process of moving all of this clay, I ended up killing 4, count ’em 4, centipedes , ranging from medium to gargantuan. Normally I would let them go, but lately I’ve been getting a lot of them in the workshop, and they have  a very nasty bite.

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.

Aging pots

Lately I’ve been experimenting with ways to age pots more quickly, making the crackle stand out. This time I tried an old woodworking trick, and it seems to work nicely.

I soaked the pots in a strong tea bath then dried completely.  After that, I applied iron acetate with a brush and let them sit a couple of days. The iron acetate reacts with tannins and turns a dark color within about 3 days. I made the iron acetate by soaking steel wool in vinegar. I may change to a weak sulfuric acid solution, since the smell of the vinegar is proving difficult to get out of the pots!

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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…