Category Archives: English

Souper 5$ a Week

I showed up in Kansas City MO for a year of school but in early July. I had $50 in my pocket but found a place where I could pay 1/2 month for a room in a shared house, “The Cowboy Hotel” is what we called it. My room was an uninsulated attic. I had about $15 left. I went to the food co-op and bought a bag of lentils that had red beans accidentally mixed in. It was a good price. I started sprouting the lentils.
I went down to The Plaza and got a job washing dishes. The owner yelled at the staff through a microphone. To say it was not polite was really an understatement. I felt bad for the nice people that worked there, but decided I would rather not go to school than be abused all day. I quit. I did demand my 2 hours of pay. I was direct and forceful about it being abusive.
I walked up the hill towards Rockport and arrived at a place called The Super. I applied for a dishwashing job. The application had all sorts of information that was unneeded for a dishwasher including college degrees, foreign languages, etc. I filled in the foreign languages: Fortran, Assembly language (this was a stretch), PLC, Treble, Bass and Tenor Clefs.
The manager came out and said, “Its boring around here. Can you come here on Sunday?” I washed dishes for about 3 months. After the first week I stopped eating lentils with lentil sprouts every day. I also became a prep cook. All the veges in soups were cut fresh. I was required to sharpen my knife to the point of being able to shave every day. Half way through I had to recheck it. I worked there for two years.
We did use a slicer attachment on a Hobart for somethings, but other veges had specific shapes and sizes. Becoming efficient was a challenge. The other prep cook was probaby 20% faster than I was.

The garden and tomatos


It is common to value things with money. This car cost so many dollars. But as someone with a job it is often better to think of things as hours worked. Say you can get buy on a $24 dollar an hour job and that you clear $20. But you see a shiny new Iphone that you want and it will cost your $100 plus $40 more monthly. That would be 5 hours of work now and then another two each month over and above what you are already working.  In a year that is 29 hours extra you have to work to have the phone. It about 3/4 of a weeks work or two weekend’s work.

There was a Co-Evolution Quarterly article on this ages ago. I did  not read it. I heard about it from a friend. It talked about the cost in hours of driving a car for errands vs the cost in hours of using a bicycle. Another similar one compared hourly costs of a new car vs a beater car including time taking it too and from repair shops. It is a useful way to look at things. Often saving money is easier than earning it. Sometimes it is not.

Anyhow, in order to stay in school and succeed I needed to not spend much money. I did spend a few dollars on a book, “The No-Fad, Good Food 5$ a Week Cookbook”Caroline ACKERMAN 1974 .  The book was written by a mother who was worried about her children. She had gone on a hiking trip with them and their friends. My memory is that it was about 4 days. They hiked in for a day and dinner came. She ate it but thought, “no meat”. Well she figured there would be some the next day. There was none at lunch. At dinner when there was none she spoke up, “Where is the meat?”. The kids said, “No meat mom, we are hiking” . She said, ” We’d better go back, we are going to starve! ” They responded , “Mom, its two days back or two days to finish, we are not going to starve.”

Her children were about to go off to school and she was worried about them. She read, and although from Canada decided that they should know how to meet their minimun US Daily Adult Requirements for food.

I used the book as a guide and for a school year I kept track of expenses and spent $3.27 per week on average. During this time I was working at The Souper and  ate a meal there and brought home about a pound of bread ends.  The diet was mostly rice, beans and inexpensive vegetables including potatoes, onions, and cabbage. But I also purchase winter squash and pumpkin when it was cheap. A 10 pound pumpkin can be had very inexpensively the day after Halloween. I bought 6 eggs every week. I made yogurt from non-instant dry powdered milk which was inexpensive because of subsidies. I sometimes turned it into Labney, or yogurt cheese. The whey went into my bread that I baked.

I made tofu a few times. I bought almost no “prepared” food although I was using some margarine to save money. I did splurge on a stick of butter every few weeks. 

This is about the time my father started in on me, “You can’t survive as a vegetarian”. I do not think a year went by when he harassed me with this. I was never a vegetarian. I even at some turkey bought when really cheap and occasionally chuck steaks. But chicken showed up frequently. He seemed to start up when he was meeting my friends. It was annoying. He knew it.

About the time of his coronary bypass operation about a decade after his heart attacks his doctor told him, “You know, if you became a vegetarian you likely would not live much longer, but you would have a better time doing it.” I started introducing him. “This is my father, Joe. He is a vegetarian.”

Freshmand from the dorms on Sundays.



Burners, Atmospheric, Considerations, Addendum on Wood

Kiln Burner Painting

Venturi Burner by Louis Katz , all-weather paint stick on plywood, torched.

Nothing in this post should be considered safety information. A lot of it is just what I think, not having read it anywhere in a format I could really understand. Other information I am consolidating.

Atmospheric burners are not understood particularly well by ceramic artists. I am going to try and clarify some things about them. I have not found any wonderful texts about them, most of what I know has been gleaned from catalogs that used to provide much more information than can be found now. While this is almost exclusively Eclipse® and Pyronics® catalogs others have entered into the mix.  To simplify things I am only going to consider Natural gas, an impure methane that is generally delivered through pipes to homes and businesses. I live in the US. So its possible that something I say will only be applicable here,,, but I can’t think what that would be.

Entrained Air
An atmospheric burner with a venturi tube is a device whose function is to efficiently use the kinetic energy of gas coming out of an orifice to carry air with it. The air that it carries through the burner is called “entrained air” also “primary air”. 

Orifice
The orifice that the gas flows out of is called the orifice, sort of a truism. The size of the orifice and the pressure the gas is under determines how many BTUs, calories, or cubic feet of gas are flowing into the burner. Orifices that are properly made and drilled create less turbulence when the gas exits the orifice and prevents loss of kinetic energy. This consequently increases the amount of air that will or can be entrained. We will discuss this further below in several places.

Primary Air
Primary air is the air entrained in the burner. The air coming into the kiln around the end of the burner is secondary air.  I guess much of this is redundant. It seemed needed. 

Flame Retention Ring
These are devices on the kiln end of the venturi tube whose job is to efficiently mix the gas and air, create a faster area for the mixed gas and air to flow through, and often provide a small amount of slower gas around the circumference to act as a pilot for the flame so that it will always light near the Retention Ring.  The faster speed is so that the mixed gas and air is moving out quicker than it is burning back into the burner. If the speed in the retention ring is too slow then you get back burning, burning inside the venturi tube. This creates soot and other troubles.

Methane – CH4

How Atmospheric burners, a mixer head where the orifice and air come, a venturi or straight tube, and flame retention ring, are sized.

The exact amount of oxygen (from air) needed to burn a molecule of methane, CH4, into carbon dioxide and water is CH4 +2O2 = CO2 + 2H20,, two molecules of O2. How much is this by volume or weight is not really important. But this ratio, we will call Neutral Combustion.

If it were only the gas we were concerned with then burners would be sized by the size of the gas orifice. You would not use a burner, and just pump gas into the kiln. All the air would be brought in with the chimney and the kiln would need to be kept at a higher negative pressure to do this. But there are two problems with this. One is that any leaks in the kiln will bring larger amounts of air in, and if they are not near the gas source then they will cool those areas, and keep them oxidizing more than anyone would need them to be. The second problem is that you need mixing of gas and air.  Gas heated in the absence of enough oxygen will produce soot, pure or nearly pure carbon. [This is hard on people contributing to heart disease, lung disease and cancer along with particulate pollution and other environmental effects.] Soot can be very slow to burn. There may be times when you want soot such as carbon trapping glazes but for the most part it is usually just wasted fuel. Assuming that the mixing of gas and air before heating is good, then this happens when the oxygen is less than 1/2 of the amount needed. CH4+O2 = C +2 H2O. In general this is a good way to waste fuel. In small gas kilns some of this burns in the chimney, but some does not. Unfortunately Carbon does not reduce carbon dioxide to monoxide, at least not easily as far as I know. I suspect that if you heat carbon and carbon dioxide hot enough you will get carbon monoxide forming,,, but I do not know enough to be sure of this. Perhaps a chemist will chime in.

[I recently found a copy of a a catalog for the  now unavailable single state Low Pressure Injectors from Eclipse. It gives numbers for 30-50% entrainment. This does not fit my memory or understanding.  Eclipse Atmospheric Injectors, Bulletin 650, 1/8/2015]

The charts that I have seen for burners being sold generally state an assumed amount of entrained air. For example; These numbers may assume that some percentage of the air needed for neutral combustion will be entrained by the burner. That is, a little over 1/2 the air needed to completely burn the gas will be entrained by the burner (or mixed in at the burner tip as secondary air). You will get some CO2 from this air, but most of the carbon will leave as CO which will still burn if more air, more O2, is provided. You only need or want a little CO for reduction. Too much and your kiln will not climb in temp and you will waste time, fuel, money. Too little will be talked about under mixing a few paragraphs down. 

The rest of the air needed is supplied by secondary air coming in around the flame retention ring. The O2 in this air burns the CO into CO2.

Why do you get more BTUs with higher pressures?


Lets just say you have a cubic meter, or cubic yard if you insist, of gas. I find it easier to image this with more gas especially when it is at a very low pressure, say 1cm water column, or 1 inch water column if you prefer. The gas, coming out of the orifice will come out slowly and will have little kinetic energy in the stream. In fact it will only have the kinetic energy used to compress it. If you use way more energy to compress the gas you will also need a smaller orifice if the gas is going to come out at the same rate. But having put more energy in you get more energy out. This energy, in part transfers to the air coming into the burner, in fact this energy is what draws air into the burner. I find it easier to visualize with the idea that the gas coming out the orifice blows air out of the burner, the air then needs to be replaced so more is drawn in. High pressure, small orifice, entrains more air because there is more “blow”, more kinetic energy, in the gas. More air means that keeping to 65% of what you need for full combustion, means you can use more gas. More gas means even more kinetic energy. Higher pressures increase the capacity of the burner. However they also increase turbulence. At some point the amount entrained in the burner no longer increases much as the pressure increases. When you get to the point where the air that can be entrained drops below 65% of that needed you have reached the maximum practical pressure of the burner.  Eclipse and Pyronics used to release good charts on their burners that mostly made this clear if you studied the numbers. 

Negative pressure at the burner port.

If  kiln is hot and the damper open you can get a slight decrease in pressure at the burner port. Assuming that the burner is placed properly in relation to the port, this decrease in pressure will allow more air to be pushed (or pulled if you like) through the burner,,, . I think of this lower pressure as sucking air through the burner. [The sucking or pulling is an easier model but is not technically correct.]  Lets assume that you make those ports too big. In order to get a given volume through them you need only a little pressure difference. As they get smaller, the pressure in the ports is going to fall. This increases the capacity of the burners because it decreases the pressure at the burner head. There needs to be enough space around them for the requisite secondary air. [100%-65%=35%]. But often these ports are made too large if the goal is maximizing the capacity of the burners so that you can heat faster.

Further the flame retention ring acts in respect to the burner port similar to the gas in the burner and carries secondary air into the kiln using its kinetic energy.

Mixing

In order for the gas to burn it has to be in contact with the oxygen in the air. If it gets hot without the air it won’t burn. If it gets hot with only a little air you will get soot. The most important mixing happens before it burns, in the flame retention ring. Burners made without them have the potential to waste a lot of fuel as soot . CH4+O2 = C +2 H2O. Interestingly higher gas pressure should produce more turbulence in a given amount of time but the gases also move through the burner body quicker. I think that you end up with better mixing, but I am not sure.  It does appear that you get better mixing with the secondary air.

About 68 percent of the heat in methane is released burning it to carbon monoxide. Knowing this makes it clear why firing closer to neutral is quicker. I like to think if firing with too little air, firing in too much reduction, as being like paddling upstream with a small paddle.

Bad mixing, too little primary air, soot, once the kiln is quite hot,  can make determining if you are reducing difficult. The soot can be burning off in the flue making flame and looking like reduction. The same can happen out spyholes. You can close down one burner’s primary air and get soot, have the kiln oxidize and have flame at the spy holes (bungs) and at the flue.

While we are on it, the flame does not come out of the kiln unless there is oxygen that is not yet combined coming out as well. The flames we normally see from uncombusted gases coming out from the kiln are hollow and start where they come in contact with fresh air. Paying attention to this, especially in wood or oil kilns can save a lot of heartache and trouble.

Heat is released when all the necessities for combustion are met, heat, O2, fuel and mixing. Well I suppose they are not in the same place unless they are mixed, but that is a fine point. The sooner good mixing takes place the sooner the heat is released. Since primary air mixes at the burner, secondary air released later in the kiln chamber. Up to a point this can be used to control temp in different parts of the kiln. 

Mixing is always imperfect. As you approach neutral combustion you should assume that some parts of the kiln are in oxidation, some reduction, as well as some parts effectively neutral. Likely with methane there is always some water gas reaction. Who knows how long hydrogen can survive in a mixed atmosphere.  There is too much I don’t know.

Wood Combustion

Part of this dynamic and discussion seems very important in wood kilns, particularly long ones. “This is what I see happening.”” This seems in part more like conjecture.” I am going to encode sentences with how certain I am of them. Sentences with fairly high certainties will have one period. Sentences where I am pretty sure two periods.. Less certain, three periods… just a working theory, four…. These are of course approximate. Some things might be substantiated by reading, some by experience, some just because they make sense.

Pyrolysis of wood produces many products. At higher temperatures these include H2 (hydrogen molecules), CH4 (Methane), CO (Carbon Monoxide) , and CO2(Carbon Dioxide) and H2O (water). Charcoal becomes mostly just carbon and ash as pyrolysis progresses. As it becomes more pure it burns more and more only on the surface. 
Before coming into contact with added air, some of the methane and water is going to go through the water gas reaction, CO+ H2O = CO2 + H2  .. This does not really change what is in the mix, just the proportions of it.

So, for me the easiest to start with is the Hydrogen. It is the easiest to burn.. It has the lowest flash point and the highest affinity for oxygen of all the common products of pyrolysis.. It burns first.. Like carbon monoxide its affinity for oxygen makes it an agent for reduction. But these two ingredients appear to have different properties of reduction of glazes.. This  appears to create some of the vagaries of wood fire.

Because of hydrogen’s high affinity for oxygen and its tendancy to burn quicker and easier it is the first to leave the stream. Because of this, it often is not likely to affect the clay. It disappears too quickly by becoming water. But one of its properties differentiates it from carbon monoxide. It is more soluble in glass than carbon monoxide.. Where carbon monoxide either needs to reduce a glaze only on the surface or only before it is melted, hydrogen can effectively penetrate the surface of the glass and reduce materials after they have melted.. This appears to be the mechanism that creates the salmon colored flashing often sought in wood and soda firing.. How this relates to other mysticism relating to the miraculous Avery Kaolin I don’t know. I am certain that Alan Watts must have done a lecture on Avery…

That salmon color seems to require a small amount of volitalized alkali metal. You can get it with both potassium carbonate and sodium carbonate is vapor kilns. It is not strictly a soda color. But introduction of water into a reducing stream of gas appears to increase the amount of salmon color.. I first heard of this from Mac McClanahan in the early 1980’s and then I tested it. It seemed true. Further use of it in my work, and my students has made me more certain..  The year after testing it I was a resident at The Archie Bray and read about the water gas reaction being used to reduce iron oxide in brick and lowering the maturing temperature of pavering block in Archie’s old library. I became a believer.

The next fuel in the mix is CH4. Given enough oxygen this just burns to water and carbon dioxide, just like it would coming from a pipe.  The Hydrogen generally goes to water first but given some existing water some of it becomes hydrogen. This is the part of this that makes me squirm and wonder if the model is correct. Some of it if mixed with air poorly or if the oxygen mix is too low becomes soot and water.  This is part of the reason that firebox design  in wood kilns seems critical. Methane burning with suffient oxygen has a blue color.

Carbon monoxide, just as in gas kilns appears to be the main reduction agent lingering in part, if you are firing in reduction, until it comes out from the kiln. The yellow orange flame at the flue or spy holes, if not the result of sodium flare, appears to be the carbon monoxide burning. Oxy -Hydrogen flames have a similar color but are much weaker in light. This can keep things confused I think. I believe that this color is more towards red, but also has a small component of blue…

It can be really difficult to determine the source of a flame color. It is important in learning to do this to evaluate the hue as this changes by source. There are several different fuels with yellow orange flames.

In a kiln, you only see flame where there is enough combustion to create enough light. I suspect that the water-gas reaction also produces light…

This brings us to carbon, soot, C, is of all of these fuels the hardest to burn. The first part of this is that it just needs a higher temperature to combust. I believe that Cardew states that this is 650˚C and I have seen other reference to 660˚C..  Cold air can extinguish burning carbon.. It also produces less heat per gram. The third is that it tends to clump when it is produced and can only mix with air on its outside layer. It has the ability to lengthen flames if the kiln has sufficient oxygen. Carbon may have an important role in evening the temperature in long single chamber kilns….But soot leaving the kiln is wasted fuel.

I wonder if having multiple stoke ports along with its obvious use in evening temperature also contributes to a bigger distribution of salmon color as it puts the hydrogen closer to more of the ware….

Burning charcoal that has lost its volatiles requires hot air. Since it only burns on the surface it goes away slowly. Maintaining the heat is critical to burn charcoal and this is one of the important aspects of Bourry box kilns. The do this by putting the location to burn charcoal after the production of methane and hydrogen and after where these gases start to burn.






Archie Bray Foundation Front showing bottles by Louis and stack of Gail's

Archie Bray Foundation Front showing Louis’ soda fired bottles and stack of Gail Busch’s in the window. Brick were fired in the brickyard.

 

Controlling Glaze Application Thickness on Porous Bisqueware.

Controlling Glaze Application Thickness on Porous Bisqueware.

Factors controlling the thickness of a glazecoat on bisque.

  1. Length of time in the glaze
  2. Density of the glaze suspension. That is how much water is there and how much suspended powder.
  3. (Apparent) porosity of the bisque, including how dry it is, how much pore space it has, how quick the pore space absorbs water, and how thick the bisque is.
  4. Rheologic properites.
    • a. flocculation
    • b. surface tension and viscosity
    • c. number of long molecules (might be covered in viscosity)
    • d. The amount of fine particles that can clog surface pores.

Length of time in the glaze

When you dip a piece in your glaze suspension the bisque ware starts to absorb water first making the glaze near the surface a more dense liquid and then turning it solid. So long as the bisque is absorbing water fast enough the glaze coat continues to thicken. As the absorption slows down there reaches a point where the coat of stiff glaze starts to get wetter again and slough off. The thicker the work is, the thicker the glaze can get and the faster it gets thick. In beginning thrown work the base of the pot is often thicker than the top making the glaze thicker near the bottom, just where running has the biggest likelihood of causing an issue.
Dipping the work in water before glazing decreases the availability of pore space for absorbing glaze. Right after you dip it the effect is greater. Because water without glaze absorbs quickly these have to be very fast dips. With work that is thicker near the bottom you can dip the bottom few inches in water before you glaze and if needed pour a little water on the inside bottom and pour it out. I do this with really runny ash glazes so that they will not run too thick on the inside.

How long a pot is in the glaze is perhaps the primary method of control of glaze coat thickness. If you imagine pushing a cylinder in for 5 seconds and then removing it for five seconds, the first part of the pot to enter the glaze will be in the glaze for ten sends and the last for less than a second. If you want an even coat of glaze, you will not have it. I use the words plunge, wait, pull. Don’t go so fast that you create a tidal wave or splash but do not take your time putting the pot in, or taking it out. After you pull it out you usually want to keep it in the same orientation so that you do not get drips down the side of the pot.
If you are doing two different glazes, the amount of time you wait between glazes controls the thickness of the overlap. The longer you wait, the drier the first glaze becomes and the more porousity it has avaialble to dry the second coat of glaze. Being ready with the secoond glaze saves loads of problems. As soon as the high sheen is gone it is usually safe to dip in the second glaze.

Density

More solids in the glaze means that the pot has to absorb less water to make a stiff coat. This speeds up how quickly a coat accumulates. Adding water can work to a point but it also increases the shrinkage of the coat as it dries. With too much water sharp edges of the clay become saturated and get little or no glaze. There are many ways to test the thickness of a glaze coat and to control it. The first measure of control is the density. How much does a given volume weigh? Adjusting that by adding water (it decreases the density of the glaze) is the first thing to do after checking if it is too dense.
Glazes should be stirred immediately before glazing. Some glaze mixtures are particulary sensitive to this. Further, since materials settle out at different rates an unstirred glaze is a different glaze at the top than the bottom. There is a particular watery look to the last part of a pot dipped into an unstirred glaze.

Rheology

The rheology of the glaze is the next issue to deal with. As you speed the absorption of the water needed to stiffen the coat and as you reduce the water needed to be absorbed you cut down on the space between the particles of glaze. At least this is the theory of Matt Katz, and it makes sense to me. This decreases the amount of air that will be trapped in the melted glaze coat and cut down on pinholes. Adding a deflocculant helps with this as it reduces the amount of water needed to make glaze fluid. Shorter dipping time also helps. Matt also favors low bisques because it increases the force and speed of water absorption decreasing the pore space in the glaze coat.
On the other hand flocculants seem to cut down the amount of thickness variation created by drips flowing off handles or bottoms of pots when they are pulled from the glaze slurry. Since you cannot deflocculate and flocculate at the same time, you have to do what is needed more depending on the glaze.

Fine Particles

Fine particles, especially bentonite, also help to keep drips from setting in thick streams. The fine clays clog the surface pores as the pot is held in the glaze. So once the glaze reaches a certain thickness the rate at which it absorbs water slows down decreasing the impact of drips as you are applying glaze. It is a good reason to add bentonite to most any glaze. Veegum does this too. Glazes with lots of ball clay do not need the addition.
Other additives such as gums, glycols, can slow absorption even further. Some of these materials affect the rheology in multiple ways. They can be deflocculants, or flocculants, they can affect the surface tension or viscosity so test them. Make sure that your kiln is vented regardless and avoid things that you should not have your hands in or are hazardous to burn.

Ways to check glaze thickness

  • Scratch through the applied glaze with a pin tool and look at the thickness of the coat.
  • Look at the glaze coat and see how it covers details,rounds off rims,  and look the thickness at the edge of the coat. This is harder than it seems and takes practice.
  • Make a thickness gauge out of a dial indicator. I am hesitant to give directions as I have not used one.
  • Make a thickness gauge out of a piece of metal with a series of teeth that will scratch into the glaze coat. I believe that I read about this in Cardew’s “Pioneer Pottery” but it could be Leach’s A Potter’s Book”

 

In order to do this you need some vocabulary, a mental scale of thicknesses. Although if you are using a dial indicator a numeric scale might make sense.

  • Light Wash. A thickness where you see more clay than glaze. The wash is only thick in recesses if anywhere at all. Likely it does not show at all on sharp edges.
  • Heavy Wash. The coat mostly covers the clay but you can see some clay showing through on flat areas of bisque. Usually it is thin on sharp edges.
  • Just Opaque. A little heavier than heavy wash, you cannot see the clay on flat areas at all although edges may show.
  • Photo Paper Thickness
  • Half the thickness of a dime
  • The thickness of a dime
  • Penny
  • Nickel (US or Canadian coin)

Drying of Clay, thoughts, experience, ideas, dynamics, principles.

Understanding the problems of drying thick work.
It would be easy to assume that drying work that is twice as thick takes twice the time. There are many confounding variables in this, and the simple picture is just not true.

It takes only a little heat to heat water up. It takes 1 calorie of heat to heat 1 gram of water 1 degree celcius. Just to get some comparison, scale in this, a kilowatt hour is 860 thousand calories. Just to avoid confusion, a nutritional calorie is 1000 regular calories.

But to evaporate water, to turn it to steam takes 540 calories for each gram. It takes time, or a big heat differential to transfer all of that heat to the water. As the water evaporates it absorbs heat from its surroundings, cooling them. This is why we sweat to cool ourselves. Evaporation of water absorbs heat.

Clay, especially dry clay is a reasonably good insulator. If you think of that 2 inch thick dinosaur as a bit of water surrounded by insulation, an inch of clay on each side, it is going to take some time for enough heat to penetrate the clay to evaporate the water. Remember, just heating it to boiling is not enough to evaporate it, you have to also get 540 more calories per gram to the water.

Below the boiling point of water at normal air pressure you can only evaporate water until the air surrounding it is saturated, until the relative humidity surrounding the water is 100%. So if you heat clay to say 90˚C or 194˚F and the clay is thick, water inside the clay will only evaporate until the air in the pores is saturated with water vapor. It may not all evaporate until there is time for the water vapor to move through the pores and be exchanged with air from outside the clay.

Explosions happen because the pressure inside the clay exceeds the strength of the clay to contain it. This part of the dynamic creates some compounding factors. As the pressure increases, so does the boiling point of water. This property likely contributes to the wide range of temperatures that we see explosions taking place at. Insulating properties of clay also contribute. the outside of a pot may be above normal boiling, but the inside might be colder from insulation and be at a higher pressure.

Fortunately, not everything makes getting clay dry more difficult. There are a few factors that speed things up. The first is that water wicks through the clay and presents itself, at least in part, at the surface of the clay where heat exchange and drying is easy. In order to understand this well you need to understand three terms, capilarity, surface tension, and viscosity.

Viscosity is the rate at which a liquid will flow. Honey and molasses are much more viscous than water. Acetone has a viscosity that is less than water, but most common liquids have viscosities that are higher. Viscosity of water decreases substantively as temperature increases. This increases its ability to move through clay towards the surface as temperature increases.

Surface tension is a nice term. It describes the tension on the surface of a liquid. When water beads up on a waxed surface the beading is because of surface tension. Without surface tension it would spread out. Surface tension is what holds bubbles intact. In mold making and in bubbly glazes a light spritz of alcohol can cause bubbles to burst. This is because even small amounts of alcohol radically lower the surface tension of the water allowing it to spread out and the bubbles to burst. Surface tension of water also decreases quickly with the rise in temperature. This allows the water to spread across surfaces, say clay particles and present more surface area for drying.

Capilarity, the property of water to up thin tubes or pores decreases slightly with increases in temperatures. The decrease is small enough that in most engineering problems the decrease can be ignored. Due to the increase in speed that this happens due to the decrease in viscosity, in our case it is more ignorable.

The loss of viscosity and surface tension presents us with an opportunity. Clay held at a high temperature maintains a more even wetness because water more easily transfers itself from wet to dry areas. Clay, in general, can be dried more quickly with few problems at high temperatures than at low. The phrase “high heat high humidty drying is used in an old text on brickmaking in the Archie Bray Foundation library and is the place I first encountered the concept. A few years later I needed to dry a thick carved mural quickly and dried most of it at 180˚F in a kiln with the lid propped over night, and some on a table with a fan. The ones on the table all cracked, those in the kiln all did not crack. I was convinced.

In this there are other confounding factors. Almost all electric kilns with the doors open tend to have colder floors. Even with zone control, unless there are floor elements this is likely to be the case. This is because cold air is denser than hot air so it settles pushing the lighter hot air out of the way. The more a kiln leaks, the more trouble there is with cold floors. Drying with the door open is an extreme case of a “leak”.

How wet work is changes the amount of time needed to dry below boiling temps significantly. It conspires with thickness to make thick objects often seem impossible to fire successfully. We have all heard the untruth, “You cannot fire thick work”. Having successfully fired kiln pugs as counterweights, I know this to be an untruth.

While I am still a believer that convection leaves bottoms of kilns colder than tops much of the problem with cold kiln bottoms seems to be the shelf near an uninsulated floor adding to the thermal mass . Work loaded on the shelf with the bottom down adds even more to this. It is not a duplicate of the area near the lid of the kiln. Dispersal of heat at low temperature has to be from convection because radiation is not very effective at the low temperatures.   Since none of these factors are very effective with low temperatures or small differences in temperature the added density at the bottom keeps things wet longer. Keeping thick work off the bottom and when possible placing it rim down vastly improves the situation by getting more of the clay higher in the kiln.

Most dispersal of heat at low temperatures in kilns is from convection caused by the differences in density caused by air temperature. The colder air heats at the elements near the bottom. This often leaves a cone of colder area near the bottom of electric kilns. So when you are preheating at 180˚F the bottom of the kiln, especially towards the center can be several tens of degrees colder. The colder it is, the less heat is transferred to the water and the slower it evaporates. Most often it seems that explosions happen in the bottoms of kilns that are fired with some, but not enough care.



Optimal conditions are unachievable. We have to fire in real situations. But if you had a piece of clay that was slightly wet, you could heat it above boiling for a short time. The water near the surface would evaporate quickly, but being near the surface would not create any pressure within the clay. The evaporation would prevent the water further inside the clay from heating as it would be absorbing so much heat to evaporate. After that surface water evaporated you would need to lower the temperature. The question is what temperature to lower it to? Optimally this might be above boiling. We only need to stay beneath the pressure that the clay can withstand. Under perfect circumstances we could even do this with leather hard clay. I believe that under normal circumstances we almost never achieve perfect drying and some water is always expelled from the walls of our clay under pressure.

Kiln pyrometers, even type S are imperfect. Even a few degrees around boiling could likely create problems with explosions. Because of this I usually used large margins. I started at 180˚F (82˚C) moved to 190˚F and as I got surer to 200˚F (93˚C). As I got close to retirement I started to use a slow rise time through boiling and shorten the hold. I believe that fine tuning this would result in quicker firings. Because there are differences in our many clay bodies and firings are mixed, “optimal” will vary even beyond considering thickness.

Sometime when I first started teaching at Texas A&M University Corpus Christi, The Island University, The only university in the US on its own island, surrounded by salt water, I decided that I needed a goal for speed of bisque kilns. How many pieces was it acceptable to explode in a semester? If you fire too slow you waste student time, and some electricity. If you fire too fast you either have not allow thick work or you blow stuff up. I decided that blowing up two pieces a semester was enough. Five was way too many. I also decided that this was true regardless of thickness. I started holding back thick work for special firings.

I dried kilns at 195˚F roughly 90˚C. How long the kiln was held depended on the wetness of the work, and how thick it was. I avoided loading thick work near the floor of the kiln. As things got busier and there were more classes, kilns were loaded less reliably. Work on the bottom started to explode more. I added time, a slow rise and then a short hold at 20˚F above boiling to try and get the bottom of the kiln to not explode. This was effective.

I started to think about the slow rise and the ability of clay to contain some pressure. I think that the optimal technique for getting work dry might be a short hold below boiling to get the work hot throughout and then a slow rise past boiling keeping the rise slow enough that the water remaining can boil without creating too much pressure. I think that this would be worthy of study. Knowlege of optimization of brick drying could likely inform what we do and save us time, money, and carbon.

intendedness vs effortlessness, consideration

It is clear to me that as a media we are making progress at least in some ways. Sure there is more technical know how and horsepower than there was 40 years ago. There is more knowledge and more people doing glaze calculation and substantive kiln innovation. But even the pots themselves are getting better. This can be demonstrated pretty well by looking at handle attachments. I have joked about looking at upper handle attachments pictured in CM from the first issue forward using the criteria of intendedness(1). But I am not so interested in quantitative research in the field. I just want to generate thought. Still it seems that progress here can be demonstrated.

In this regard I have been looking at Simon Levin’s handles on cups. Really the whole cups are wonderous but it is the handles I am most in to. The mimicry of the smooth upper attachment is so well done at the bottom that the effort that goes in is not apparent. There are no signs of any effort. The bottom attachment looks as is it was accomplished the same way the top attachment was, no muss, no fuss. But it wasn’t. Simon has apparently developed the skill  and technique to make the bottom attachments look the same and a lot of effort went into this.

The lack of unresolved details in the bottom attachment meet my definition of intendedness. Every part of the attachment looks like it was considered. The details look like they were all intended. The clean lack of struggle, the lack of unintended marks, makes these lower attachments look effortless and I wonder if the terms “apparent consideration”, “intendedness” and “apparent effortlessness” are not in some ways relating to pots, synonymous.

(1) Intendedness: This is the appearance of intent, rather than intent itself. Something can look like it has intent but if it is actually accidental, or a controlled accident it still has intendedness. The Bauhaus  designers used to say that every aspect of a design needs to be considered. This is an important principle, but in my opinion poorly stated. I say that every aspect of a design needs to look considered or intended. They do not need to be intended. How well something conforms to this ideal, this look of intention or consideration is its intendedness.

Once something looks intentional it is possible or easy and almost automatic to either think you know why something was chosen the way it was or to wonder why. Either of these is a gateway to meaning.

 

Din Phao, Din Phao: ดินเผาดินเผา

2014
Dankwean Dinpaw , the sales area on the road is hurting. Based on quick appearances……..There has been an incredible building of sales malls. People are still building them despite lots of vacancies. Perhaps, hopefully, people believe that sales will improve. The old large potteries are falling into disrepair. Umdang is closed essentially and the business that they do is via phone sales and visits to sites where they design installations, murals and bas reliefs. The have almost no road sales except perhaps tiles.
Chao Din (people of the earth) seems to still be producing murals, but the bustling stream of visitors and buyers seems to have ended. Its once immaculate display area is getting funky. The fish pond is full of algae and the air and water pumps not working. The koi are oblivious, but as a visitor it is not nearly as nice looking.
The old professors are dead. Ajahn Pit who was always welcoming and nice to me died a few years ago and his daughter and son took over for a few years. I am told that they are now in the US. Like Chao Din the once brilliant and organized display of Ajahn Pit’s Din Phao has seen better days. Eddie McGrath wrote that there is a tendency in restaurants to rather than keep up on maintenance to just “let it go” and sell out to someone who wants to sell cheaper food and build a newer restaurant. The tendency may have some similarities here, but it is not working, Only a few nik-nack shops across the street seem to be doing well with street-side sales. I have seen several places packing work up for sale elsewhere.

Ajahn Wirot from Din-Dam has been dead for some time and his once chaotic display and museum is hard to see among the weeds and behind the distracting buildings. It would surprise me to find out that any sales at all were going on there.

Across the street from Umdang there is a place where tour busses stop because the displays are clean. They sell espresso there for 45 baht and about 100 yards away it is only 25. There apparently are people buying little nicknacks still.

The hand skills on the “traditional” carved surface Dankwean pots have continued to improve. There is truly some incredible carving going on. I hope that the scrafitto workshop really takes hold as this would help create an opportunity for these skills to translated to fired surfaces. That said the painted surfaces look better and better every year I visit.

Up Wind

2014 Prep

I am preparing to go to Thailand. I have lists and even a list of lists. I have packing lists, lists of paperwork to duplicate, lists of people to contact, letters to write, and files to transfer to the laptop. Oy.

But there are other preparations I have to make. They may be more important. I must slow down, remember the Thai manners, the cool heart – jai yen, slow, controlled not too excited. I have to remember to slow and greet people properly, the smile and the ability to let things roll off my back with a smile on my face. It is not just smiling that I need to do, but the smile state of mind.

The idea that desire is the root of suffering, that grasping creates disappointment, is at the heart of this change. It is a part of Buddhist philosophy but, it is so widely accepted and implemented in Thailand , that you have to succumb or find yourself swimming upstream. I no longer can swim upstream for months at a time. I have to smile, go with the flow, allow the troubles, the hurry, frowns, worries, to flow away, to touch perhaps but never stick. I have to learn to “mai pen rai” . To activate the phrase “its not a problem or worry” you have to make it a verb.

I have a huge agenda. It is work. It is too much. It would be good if I could get it all done. It is almost certainly undoable.  An agenda like this can add an off flavor to everything. It can prevent months of work from being productive, too much stress on doneness not enough flex to contemplate, think, digest,,,. I have to start by doing “mai pen rai” by turning off the worries and allowing the future to come. You can only swim upstream so long.

I  have to even stop my little social concerns. Did I fail to slow down and say Sawasdii, did I remember to call them “elder”, was I polite enough. I have to do this because really the first politeness in Thailand is to mai pen rai. It is a necessity like air. When you do this, the little stuff comes easy, and the hard stuff is easier.

 

Thrift Store Pots

I arrived in Helena with Gail and the boys. If I remember correctly Benny was an infant. I was supposed to be on a quick run to the Rock Hand Hardware Store but guiltily I stopped at a thrift store on the way. I did a quick run through the hardware area. I never buy clothes, well, hardly ever. I walked down one of the isles with pots and turned them over to see if any were made with clay bodies (compositions) from before the 70’s. One ugly little cup with a funky dead form, coil handle, poorly turned footring and bubbled glaze, that was rubbed down with a brick to break the bubbles, was old stoneware. It did not have the typical APGreen brand fireclay look. It was ugly so I set it down.

By the time I got to the end of the isle I was thinking again of the ugly pot. “Whose signature was that?” I went back and turned it over again. Clearly it was signed, “Voulkos” (right).
IMGP5147RosieVolkoussm
Peter Voulkos is one of the best known clayers of the 20th century. He made delightful functional pots until he began making abstract sculpture. He began studying pottery at Montana State University in Bozeman under Francis Senska and was a resident artist at the Archie Bray Brickyard. After Berard Leach, Shoji Hamada and Soetsu Yanagi lectured and demonstrated at the Bray (not sure of this it could have been before) the resident artists at the Bray were asked to make “Bray Standard Ware” (I need a source for this). One of the items was a small cup with a little coil handle just like this one. Voulkos, I think, resented having to make these, but made them. In defiance, (again conjecture) he signed his cups.

(Yanagi, Leach, Rudy Autio, Voulkos, Hamada, at the Bray Pottery)

Cup in hand, poker-faced, I paid my 25 cents and left with my cup.

A few months later at the same store I bought a cup by Rosie Wynkoop (left) who had been one of my students in the community classes at the Bray.  It cost a dollar. I think she made it while she was one of my students.

In graduate school one of the off syllabus things we learned was that garage sale and thrift store shopping was a competitive sport. The price tags were left on the pots. One friend was so well known at one thrift store that she received phone calls on the store phone.

On occassion, I invite my students over to my house to view pots. One time while talking about these two drinking vessels a student asked, “Wouldn’t Rosie be upset to find out that her work only cost a dollar?” I answered, “No! She is getting four times the price of Voulkos!”

Burnt Coffee

So, my second daily pot of coffee… I was brewing with the radio on.
Distracted. Boiled over.
Burnt coffee smell of my father melting the percolator.. but without burnt bakelite handle.
I opened the front door… 10 years old. Dad at work. It stunk but was not smoke so I went in.
Aluminum slag. Time for a new coffee pot.
Turned the burner off.
Smart kid.
Nother day.
Came home from school.
Opened front door. Smelled smoke.
Went next door to Sheri’s house.
“Mrs Simons, could I use your phone? ”
Dialed zero. “Operator give me the fire department.”
They came, no smoke.
“So, you decided to see the fire trucks little boy?”
Mother, Fern Katz , pulls up next to the fire truck.
“My son said there was smoke, so there was. Go find it.”
Mom gets extra credit and gold star.
Lint in the dryer caught fire and went out.
No one asked me how much smoke.
The coffee is good. Time to clean the stove top.

Appon’s Thai Food Site https://www.khiewchanta.com/

 

Appon might be an old Thai pronunciation of Apple in Thai. The letter that corresponds with ‘L’ ล (law ling) is only pronounced like an English ‘L’ as the initial consonant in a syllable. At the end it is pronounced like an English ‘n’ in Thai. Consequently ‘hotel” becomes ‘hoten”, and ‘Apple’-‘Appon’.

Regardless, the recipes on her site look to me like the real deal. They are not what you find in most “Thai Restaurants” in the United States. Chicken Feet in red sauce, and Haw Mawk Prik Kai  and Kanom Jiin Nam Ya Tin Kai are on my list to try.

https://www.khiewchanta.com/