Happy New Year

The fall anagama firing seems like quite awhile ago.  The end of semester work load (mainly on Janelle's shoulders- with help from Vincent) was quite a crush thanks my needing a new left hip.  All has gone well. Many thanks to Janelle and Vincent for filling in.  They are the best.

The was our fourth firing.  We continue to learn a great deal each time.  This firing was no different.  First, we were determined to take this firing to 40 hours wanting more heat work and ash deposit.  We came within a half an hour of our goal. We were able to extend the firing just fine without over-firing the front of the chamber.    As mentioned in an earlier post, we saw the effects heat work in action.

Second, we took a different tack toward getting heat to the rear of the kiln.  Previously, we raked coals from the fire box toward the end of the firing to create room in the fire box for air to sweep over the coals. Create a hotter firebox, then draw this heat to the rear.  In addition to the open airports, we were opening the stoking port to give the kiln as much air as possible.  Air = heat!  This contributed to more heat alright- concentrated in the front of the kiln.  And hot coals at our our feet made stoking tougher and more tiring- not to mention the need to put the hot coals somewhere.

We found that raking hot coals is not necessary at all.  In fact, it makes little sense when the idea is to get as much heat from your fuel as possible.  A lesson I learned when younger (rake as few coals as possible) is taken to the logical end.  So we have made life a bit easier by being a bit smarter and patient.  It's these little things that experience brings.  I especially like solutions that repair more than one problem, in this case- no coals to deal with and moving heat (work) to the rear of the kiln.

We stirred up the fire box regularly to keep the fly ash moving and to keep the surface area of the burning wood exposed to as much air as possible.  This also was a better way to manage the coals.  So patience in stoking and letting the firebox work was the key.

We also used quite a bit of pine bark at the end for color.  I am not sure of the result- willhave to do it again.

We didn't use the Troy body this firing since the clay shipment didn't come in time.  We plan to experiment with it more next time.  Maybe the bark will have more of an effect on the lighter body. I like a darker body, but it would be nice to have a bit of light burning stuff to play with.  I find the bodies that seem popular now like the B Mix seem to be on steroids, loaded with plasticizers.  The Troy body is similar.  Good for simple full forms and great for surface marks and tracks.  I find it difficult to make pieces that demand more from the clay, some tooth (the folded walls I like are too thick- maybe with more time I will get it).

I want to play with some things like lithium wash and soda ash to see what happens.  Making a slip out of the Troy body might be interesting also.  And the old stand-by of Rutile and G.B. is always good.

The Master

We will be posting images and comments on the wood firing shortly. I ran across some images of our man Vincent Clemente, retired professor of art here at PrattMWP, and the dean of potters in the Mohawk Valley. Thought I would share them. He is demonstrating for my sophomore throwing class. At 86, he is still an integral part of our wood and salt firings.

For more information on Vincent, see the May, 2008 issue of Ceramics Monthly.

Salt Firing fall '09

Thanks for this image, Grace.

The weekend salt firing was quick and sharp. Starting it at 7:00 pm Saturday and firing it off at 5:00 am Sunday reminded me of the firings we would do in Oklahoma during the summer. It would get so hot during the day we chose to fire through the night and finish at dawn to beat the heat.

The insulating fire brick (seen in the image) take a beating. We have been able to coat them on the inside (hot face) to keep them from deteriorating too rapidly. The spy holes are another story. Looks like a good spot for castable repair.

The anagama is still cooling some 3 days after...

Have been reading the latest edition of the Log Book . We knew Jack's article was going to be in it. I still find it hard to believe he lost interest in salt firing. The traditional approach to salt can be somewhat one dimensional, true, but vapor has so many variations from ∆ 03 up. It is so versatile. I have fired terra cotta at ∆ 03-3 with great results. In fact, I was looking for a similar surface to the Voulkos' platters while in grad school that lead me to experiment with low temperature vapor back then. Soldner used vapor in raku in the 1970's. There is so much to try. And Jack's excitement when holding pieces from our collection certainly gave you the sense he was still smitten. But as artists, we have to follow our gut as well as our head.

Speaking of raku- it too has endless possibilities if you get beyond the tired stuff of the past 2 decades. Going to commercial glazes is too easy. The "flash" factor is still alive and well unfortunately. Try using darker bodies and spraying on frits and clays and borax and lithium and ochre and on and on...

We are knee deep in a baroque fashion in American ceramics. Nothing wrong with that I suppose, but the band wagon is wide and deep. Always has been. I was a product of abstract expressionism (the last great dominant movement, I think- the post, post, post, modernist era is still up in the air, due to the need to label such movements immediately, sucking the oxygen out of the air) and the far eastern aesthetic which some today may find tired and lacking. But the subtle is permanent, flash is temporary.

Afterburn

After 39 1/2 hours we brought the wood firing to a close. We were able to soak for close to 7 hours allowing the back of the chamber to reach a solid ∆ 9. If there is one human trait that often trumps all others, it is patience. "Heat work," that critical, almost magical element is the reward for letting the kiln do its work without pushing and prodding.

It is particularly satisfying to show students this mystical process, after talking about it so much. The pyrometer and cones in the rear of the chamber confirmed our trust in the kiln and rewarded our commitment to continue stoking.

For our "soak" we decided to stoke to keep the rear at a steady 2100º F (not wanting the front to run away) and let the kiln do the rest. We finished stoking with pine bark for color. We shut it down after reaching cone 9 in the rear with the pyrometer still reading 2100 plus or minus.

Just as the lighting of a wood kiln is quiet and ceremonious only to the degree we want to confer, the end of a wood firing is equally so. Simply stop stoking and close up the kiln. No switches to turn or burners to shutter. The very instrument of all our constant and tiring attention simply winds itself down with no fanfare other than any we might wish to perform in front of it, assuming the energy is still there (and more likely to happen if given some thought before the lighting).

Once again we fired the salt kiln on the last night of the wood firing. Smoke and vapor everywhere. And it would not be complete without a visit from the UFD. They are always gracious and even curious at times. We are always very thankful they show even if we give them a heads up. You never know.

Fall Anagama Firing '09

Just a quick note- we are in the 31st hour of firing the anagama. We are at about 2100 degrees in the back of the chamber and climbing well. Our goal is to get above cone 8 in the back in the next few hours and continue the climb leading to a soak of 6- 10 hours.

More to come...

Upcoming Firings

We will be firing the wood kiln in a few weeks, loading early in the week of November 16. The plan is to start the firing on Thursday the 18th and fire till Sunday evening. We will be firing the salt kiln that weekend as well.

We hope to fire the wood kiln longer this time, getting more heat to the rear of the kiln and more "heat work" in general. When we visited SU last week they remarked how Jack had fired their anagama long and with little air. Makes sense- if you want to get heat to the rear, lengthen the flame. We have been making slight adjustments to that end as well.

SU's kiln has a very deep and tall firebox relative to the ware chamber. Never quite noticed that before. Although it is a hill climber (stepped chamber), the crown is level. Troy brought hardware for setting up a grate in the fire box. There are a number of pros and cons for this. In the case of the SU kiln, it seems that you would get more flame to the crown which would help draw heat up and over to the back of the chamber. You can get fewer ashes and coals as well. But patience is the key. A longer flame helps keep things even. Pots and bag wall placement/height matter as well. I am not sure about the stoking ports to the rear of the (SU) kiln. It seems they are so far back that you are feeding the stack, not the ware chamber. They are talking about creating an air port for the rear stoking port, but it still seems that you might be doing things a bit late in the chamber (ps- Henry Gernhardt, SU Prof., had suggested an air port in the rear when the kiln was first built- I defer to him!). Noborigamas don't have after burners. And the effects of a "check draft" need to be considered.

Feeding the stack has always been a question for me. A long flame does just that. But an even kiln is usually the goal. The trick is to strike a balance. The stack is a tool, not a chamber. But it is fun and dramatic to "candle" the top of the stack. There is so much to discuss here. We have a "secret chamber" between the main chamber and the stack which we have yet to experiment with. Part of the excitement is the variations in approach. Maybe someone has some ideas to bounce around.

We originally planned a grate on our kiln but opted out. We were tired and wanted to get on with it. We also knew of wood kilns without them that fired fine. I think it is something we will eventually try (our kiln chamber does not step up like SU's- our fire box is lower than the chamber; the crown is level). I do think the coal/ash amounts can be managed either way. One of the first things I learned years ago was not to be so efficient in pulling coals from the fire box. It is tempting- but you are losing valuable btu's.

Air is another issue. A wood kiln is the same as any fossil fuel kiln, but the reads are a bit different. For example, a lot of flame at the ports and damper means reduction in a gas or oil kiln, but not necessarily so with a wood kiln...

At SU they use the same phrase we do- "we are just learning about this kiln." Great fun.

Water and clay

I was reading somewhere the other day about water and throwing. The article was about the notion that too much water is bad for the walls of a pot and weakens it. I immediately began thinking about the various "wives tales" that seem to survive generation to generation without skepticism. This is one. Flat out- you can not use too much water when throwing. But that statement makes one important assumption, that you are using good technique.

The explanation goes like this- the walls of a pot are built as a result of compression or pinching the clay between the fingers or any other relatively narrow point of the hand (I have known potters to use the knuckle or thumb, for instance). This means the compression points must be directly opposed. You can't have compression any other way. In doing this, you assure the wall is as strong as possible (tight) and as such, it just cannot take in water. I suppose you might be forcing a bit of h2o into the surface of the wall in any given pull. But you are also clearing the wall of water as you bring your fingers up (the pull). The wall is always dryer beneath the pull. The key is compression (we will make the distinction between a compression pull and a shaping pull in a later post).

Here is how wall weakness begins- if you lose compression you are stretching (tearing) the wall (in tension) which is literally opening the wall to water penetration. You lose compression by letting the inside contact point migrate above or below the outside. The wall is weakened from the stretching. Water will exacerbate this weakening, but it is not the culprit.

The second important point is that water is used to lubricate. And slippy water is a better lubricant (to a point) than fresh water. So always add water to your water bucket rather than starting over with fresh tap water. Throwing slip is high(er) in solids which do not penetrate the surface of the wall (in fact they align parallel to the wall, which helps lubrication). As the throwing slip loses its ability to "sheet" the wall, add fresh water to it.

Clay is often used to protect surfaces like a cellar wall from exposure to surrounding ground water. The clay is compacted in and around the basement. But another test is easier to carry out. All potters learn very quickly that dry clay sucks up water very fast. Remember the pot that got to dry to trim? Putting green ware in water will leave you with a dissolved wall inside of five minutes if not sooner. Do the same thing with leather hard ware and you find the time it takes to soften is longer. Water moves through clay by capillary action. But you need capillaries. The denser the clay (wet and well wedged) the smaller the capillaries.

So the problem is not directly the water, but losing compression on any given pull. This happens when the fingers are not directly opposed, creating a tension or stretching of the wall as it is "folded" through the fingers. This allows water to infiltrate the wall and the wall to weaken. From a teaching standpoint, the rule is still to use plenty of water. Learning to throw is tough enough without having to fight the drag that dry throwing creates.

Finally, to throw without water is no doubt a virtuoso performance. But I can't help but feel the walls straining between my fingers, torquing at a greater rate than lubed clay and being stretched unmercifully. Having said that, I still am amazed at the skill some possess. I remember the great California potter, Michael Frimkiss demonstrating his dry technique many years ago at Supermud at Penn State. What a touch. But I think he could do it wet as well as he could dry.

Add to this discussion, please. I know there are other variables like grog content and plastic clay content, form, shape and wall structure. The order of wall construction (top/down, axis/out) is another topic very much related to this. Would love to hear them.