New Year, New Foundations

HAPPY NEW YEAR!

YES! We have begun the foundations for the kiln shed and kiln! Now that the family are truly safe and settling into our own home, I can start the task of getting my work back on track. It is, of course, the firing of the kiln that finally defines the potter. So, after ten months in limbo, the joyous rebuilding begins!




In the corner of the front yard, behind the existing shed (which is currently home to a bevvy of cats) and at the end of the driveway, is a triangular space begging to be used. It is away from the house, which is important for fire safety, but much closer to the studio than my kiln was in Mashiko. It was always a challenge carrying pots to the kiln during rain, as my vessels are glazed raw and even one drop of rain can cause the glaze to crawl. During the four months of winter here the issue will be snow, which is unfamiliar territory for me. The first time I saw snow was the day I arrived in Japan, 22 years ago next week, and even in Mashiko we only had two or three snowfalls on average each year. It has been snowing to a greater or lesser degree every day here since Christmas, and I am told to expect at least a metre of snow by February. The children have been having snow ball fights and building snowmen and igloos to their hearts delight, and there is no greater joy than to hear children's laughter echoing through the flurries of snow in the garden.




I had arranged for the local contractor, Shimojo san, to start the foundations last month, before the ground froze, but the best laid plans...

As fate would have it, he arrived first thing in the morning on January 11th, and amid light flurries began setting up his theodolite.



The first day was spent taking levels, setting squares, driving pegs and putting up the outer guide frame. The kiln shed will be 3.6 metres wide by 4.5 metres deep. Once the outer framing was completed, he parked the back hoe ready for work the next day. He assured me that we can complete the job despite the snow, and I must trust him on this as he was born here and knows his craft well.




By 6:00AM the dawn lights the sky with amber and gold beyond the mountains to the south east, those mountains we crossed ten months ago, but the sun does not show its face over their peaks till after 7:15 as the kids go off to school. At 8:00AM the work begins in earnest. Excavating with the back hoe to lines drawn in calcium on the snowy ground, it is hard to tell the calcium from the snow! As the sun warms the ground the snow begins to melt.




By the time Sean is ready for preschool the main excavations are well underway. I cannot help but dance for joy, and Mika happens to catch a snap shot before I realize I'm being watched! It has begun, after all the trials of last year, it has begun!




A five centimetre layer of gravel is spread over the foundations next. We use recycled crushed concrete, rather than new gravel. Apart from my stance in terms of recycling for environmental reasons, it's cheaper! The truncated pyramid form of the foundation and the gravel are important for proper drainage.



The gravel is compressed and compacted with a vibrating roller, and levels are rechecked.




Once compressed, a damp proof sheet is spread over the foundations, and set in place with 5 centimetres of concrete.



Patches of concrete on top of the damp sheet will act as supports for the steel reinforcing. By 3:45PM the sun vanishes through the trees beyond the ridge to the south west and ice crystals stretch their talons across the puddles from the melted snow in the driveway. Shimojo san covers the foundations with tarpaulins, and assures me it will be OK overnight.

Overnight was minus 11 centigrade, and the tarpaulins are frozen to the surface of the concrete. I wait with baited breath for Shimojo sans arrival. "No problems," he says. "It's perfect."

Day 3, today, we frame the outside with the formers for the concrete and set the steel reinforcing. One of the many lessons which I learned from the earthquake was the importance of a strong foundation. That is why I have asked a professional to do the job.

The square and level are checked and double checked.

Steel reinforcing rod is set at 20 centimetre intervals. The total weight of the kiln will be about 7 tonnes, and the reinforcing has been calculated to support that weight. Anchor bolts for the kiln shed are welded to the steel reinforcing. The house in Ichikai was not secured to the stone footings, so when the earthquake hit the whole house was shaken from it's foundations. The angle iron frame around the kiln will likewise be anchored to the concrete this time, but those anchor bolts will need to be embedded later. It is important to learn the lessons from our experiences in order build a better future.

On the level, on the square, framed and reinforced. We will pour the slab on Monday, and it will take at least a week to cure. I hope to begin the kiln shed on the 23rd of January, and build the kiln in February.

My plans, however, are not set in concrete. I take each day as it comes, grateful for my blessings, and I know that I am moving forward. I know how suddenly circumstances can change, and so I hope for a bright future, but I am taking care to build it on a strong foundation.

Feet of Clay

When firing a wood kiln, or salt or soda, one of the challenges is preventing the feet of the vessels from sticking to the shelves. In any of these firings the atmosphere in the kiln is full of glass making materials, either as fine particles of ash or gaseous sodium trying to flux any free silica in the clay to a liquid glaze. In fact, that is our objective, and by allowing this flow of glass making materials to wash over our vessels we invite nature to glaze and decorate our work for us. It is difficult to be selective, however, about where those gases or particles flow without sacrificing the spontaneity of the glaze effect on the whole vessel. If the liquid glass flows down to the foot of the vessel, then when it cools the foot will be stuck to the kiln shelf by solid glass. This is difficult to remove without chipping the piece or damaging the kiln shelf, and such losses can become quite expensive.

There are several ways of addressing this challenge and I employ two methods in my kiln, depending on where the pots are to be placed. The first is to try to prevent the pots from sticking. My first step in this process is to design my feet so that there is a minimum amount of surface area in contact with the kiln shelf. The foot ring itself is trimmed with a chamfer on each edge so that only a thinly angled line touches the shelf. This also creates a slight overhang to help prevent fly ash from getting under the foot. When the vessel is removed from the kiln the foot ring can be touched up with some sand paper and "Viola!", a nice smooth foot ring. When I am waxing the feet of some vessels before glazing, on plates for example, I use a special wax mixture of candle wax, kerosene and a handful of alumina powder. The wax burns off in the kiln, leaving a very fine residue of alumina between the vessel and the kiln shelf. Alumina (Al2O3) is a highly refractory material, the melting point of which is about 2040C, and so it remains as a dry powder even at glaze firing temperatures, and will serve the same purpose as flour on the work bench when you are making pastry or bread, preventing sticking. Following the same train of thought, Alumina is used as a coating on kiln shelves and kiln furniture to prevent sticking, just as flour is used on the inside of a cake tin. On its own, however, alumina floats around as a powder and can stick to glaze surfaces making them matte and unattractive, so a coating mixture containing some clay material as a fixative is necessary. The mixture which I use is Alumina 2: Kaolin 1 proportionately by weight, mixed with enough water to make is a pourable creamy consistency. I put this into a watering can and pour it over the surface of the kiln shelves, then put them out in the sun to dry. After every firing I scrape any accumulated ash or soda deposits off the kiln shelves, so that they are ready to be coated again for the next firing. It is important to use a dust mask and eye protection during this process! The materials are all non toxic, but inhaling dust can cause lung disease, and chips of broken glass in the eyes should be avoided at all costs!

My other approach to this challenge is to accept that a wood or soda firing is what it is. There is going to be ash and glass dripping of the pots, and it's going to leave marks. If you are trying to avoid that and it happens by accident it can leave nasty scars on the pots. If, however, you accept it and allow it to happen as a part of the total design, those marks become cicatrices, like tribal scars, and a beautiful expression of the firing process in the finished work.

I do not use wad mix directly on the clay, as that goes in the nasty scar basket. Instead I use a ball of fire clay, rolled in alumina, stuffed inside a sea shell. A set of three, or sometimes more, of these will form a stand on which the vessel can be placed, raising it off the kiln shelf. When the kiln is fired, the salt in the shell will volatilize off leaving flashing marks on the clay. The Calcium Carbonate (CaCO3) in the shell will lose Carbon Dioxide (CO2) and become Calcium Oxide (CaO), still retaining its original structure between the vessel and the fire clay. Any glaze, ash or soda will flow into the shell structure. When the vessel is removed from the kiln and placed in a bucket of water, the Calcium Oxide (Quick lime) will rehydrate to become Calcium Hydroxide (Ca(OH)2 or Slaked Lime), and will just wash off the vessel leaving a fossil like cicatrix where it was in contact with the surface. The slaked lime goes on the compost heap. A touch up of the sharp edges left on the glaze deposit with some sand paper, and Robert is your fathers brother! This is the method I use at the fire face, where the forces of nature are most energetic and capricious. I described this process and my feelings about it in my "Art for Eternity" entry, and I invite you to read that by all means. The greatest challenge for a potter, however, is knowing when to take control, and knowing when to surrender it. It is this balance, this dance with the elements, that creates such beauty, that gives great joy to the user of these vessels, and makes being a potter such a fulfilling career.

Sake Cups

As western culture often speaks of "Daily Bread", here in Japan the staple diet of rice is so ubiquitous that the word for rice and meal are the same..."Gohan" (御飯), or more informally "Meshi" (飯). Rice is used for making a huge variety of other foods, one of the best known of which is, of course, "Sake" (酒), or "Nihonshu" (日本酒) the Japanese rice wine. Our local Sake is Souhomare (惣誉), one of the best in the prefecture. There are makers of Sake, called "Sake Gura" (酒蔵), in just about every town in Japan, and there are a huge variety of types and styles. Some are clear, some cloudy, some should be drunk warm, others chilled. Thus, because there are so many styles of Sake, there have developed a wide variety of cups from which to drink it. Probably as many as there are potters in Japan, so here are just a few!

Probably the best known style of drinking sake is the warm Sake called "Atsukan" (熱燗) . Strictly speaking, Atsukan should be 50 degrees centigrade, and often it is heated to disguise poor quality sake, but there are types of sake that are designed for this temperature. Any warmed Sake is called "Kan" (燗), but each temperature has a different name. 33C is called "HinataKan" (日向燗, Sun Warmed) , 37C is "HitohadaKan" (人肌燗, Skin Warmth), 40C would be "Nurukan" (ぬる燗, Luke Warm), 45C is "JoKan" (上燗 High Warmth) and, for those who like it really hot, "TobikiriKan" (飛び切り燗, Over the top!) at 55C. Atsukan is usually a winter drink, so to make sure that it doesn't cool too quickly it is poured in small quantities into Sake cups called "Choko" (猪口, Boars Snout), which has a high foot shaped like a boars snout and a small, deep bowl. They can be lacquer ware or ceramic.

There is, however, another style of "Choko" for cold Sake. It is basically cylindrical in shape, so that the whole cup is shaped like a boars snout. These two cups were made by Masumi Narita, another Mashiko potter and Sake lover, and one of the important points about these cups is the fineness of the lip. Sake cups do not need to be identical to be a set, they merely need to share a common theme. There are some people who believe that the "Choko" name refers to the small quantity consumed with each cupful ("Chokotto", means "in small increments"), and I wouldn't be surprised if the Japanese traditional love of puns hadn't influenced the original naming.





It is usual for sake cups to be sold as pairs or sets of five. Four is an unlucky number, as it is a homonym for "Death". These two "Choko" of mine came out of last weeks firing. (They are available from my Gallery here.) "Cold" Sake is called "Hiya" (冷や), and is drunk at room temperature like wine. Colder Sake would be "Suzubie" (涼冷え) at 15C, "Hanabie" (花冷え, Blossom chilled) at 10C and "Yukibie" (雪冷え, Snow chilled) at 5C.




Everyday general purpose Sake cups are called "Guinomi" (ぐい呑, Gulping Cups), which are named for the sound one makes when one swallows. The small Guinomi would generally be sold as a set of five, to be enjoyed at a gathering or with a meal. The two front Guinomi are by my Sensei, Tatsuzo Shimaoka, National Treasure, and were shapes which I was trained to make during my studies with him. The one at the back is one of a limited edition which I made to commemorate my exhibition at Ebiya in 2000.


The larger Guinomi would be sold individually, and a serious Sake lover would have a wide variety of them to select from depending on the style of Sake, the season or their mood. A sake cup like these, again by Shimaoka sensei and myself, might be used for "Nigorizake" (濁り酒, cloudy sake), which us unfiltered and milky white.





For more formal situations it is traditional to use a shallow bowl shaped cup called a "Sakazuki" (盃). This would only be used with the best Sake, crystal clear and usually cool. This is a silver sakazuki from the Imperial household, as can been seen by the imperial crest in the centre of the cup. A pattern is often made in the centre of the cup so as to emphasize the clarity of the Sake. It is very nice with a "Yukibie" on a hot, steamy summers day, just like today.

Surface Tension

We take the forces at work around us for granted most of the time, hardly realising that everything in nature, even a drop of rain, is as it is because of universal forces. Forces and structure pressing outward, weight and pressure pressing inwards, and the point of balance between those forces, the border line that defines a form, we call the surface.


When forming clay on the wheel, it is the task of the potter to remain still while those forces work against our hands and find balance in the shape of a pot. Once taken from the wheel and allowed to dry partially, the clay shrinks and there is a certain tension in the surface when the pots are returned to the wheel for trimming. The trimmed surface is therefore different in character than the unaltered thrown surface. I have always found the play between these surfaces delightful. I therefore try not to interfere with that too much by cluttering it with decoration.


When doing a collaboration with a french restaurant a few years ago, however, I needed to add a rim motif. I am not one for drawing pictures of things on pots, so I created a small design which extends the idea of surface.

If one scratches a line in leather hard clay, the edges will tear, leaving a jagged and messy edge. If you cut the same line with a sharp tool so as to pare away the clay the edge is sharper and far more energetic. Using a hoop tool with an acute angle I cut an exclamation mark. Below that I add three dots, compressed with a cone shaped wooden tool. As the clay from the dot is not removed from the surface it moves into a raised crater like edge, giving these indentations a different textural character than the cut mark.

Beside these incised and compressed marks I add, literally, a drop of slip. Slip, or engobe, is a liquid clay used for decoration. In order for the slip to be compatible with the clay I use the same porcelain for the slip as that which constitutes 75% of the clay body. The shrinkage of the slip is, therefore, exactly the same as the clay, so there is no chance of cracking or flaking. One slip I make fairly viscous, and add 2% of Copper Oxide. I apply this with a thin metal rod as a single drop, touching the end of the rod to the clay surface and allowing surface tension to pull the slip into a circular droplet on the rim of the bowl. I prepare a second engobe which is thinner, with 2% of Chrome Oxide, and, using the same metal rod, I touch a droplet to the surface of the pot then flick the end of the rod away, once again using surface tension to create a dynamic elongated tear drop shape.

These applied engobes give a raised pattern which counterpoints the intaglio incising and impressed marks on the rim. When fired, the pure porcelain of the engobe becomes slightly glassier than the clay body. The Copper becomes red in the reduction, a form of "Shinsha" glaze, and the Chrome becomes green. Combined with the flame colour of the clay, the Igusa straw markings and tenmoku glaze, this small motif adds a subtle and dynamic accent to the rim of the vessel which is rich in visual and tactile information.


We interact with nature and the world around us on many levels, and tactile beauty is just as important in art as visual beauty, more so for those without the gift of sight. By utilising surface tension and the forces of nature, energy and tension can be expressed intimately in the surface of a vessel.

Legal standards for functional ceramics in Japan

You may remember by blog entry "Safety First" , concerning the food safety standards for functional pottery in Japan. I have been asked by some of you for more information about this, so I have read the notification in the original Japanese and the following is my brief interpretation of it in so far as it applies to functional ceramics. The law applies to Glass, Ceramics, Enamel and other food vessels and packaging, so I won't deal with the full scope of the law. I am, after all, Euan the Potter.

According to notification #416 of the Japanese Ministry of Health, Welfare and Labour, as of the 1st of August 2009, it is required for all manufacturers and importers of ceramics for food to conform to the standards set by the International Standards Organisation for levels of heavy metals, specifically Lead and Cadmium.

These safety levels are based on the amount of Lead and Cadmium which can leech into a liquid from the vessel under set test conditions. These levels and conditions are set out in the second table on THIS LINK.

The levels differ slightly for vessels which are used to heat food and those which are not. However, Sake bottles (tokuri), Chawan Mushi Chawan (vessels for savoury steamed custard) and other vessels which can be used to heat or reheat food by any method not exceeding 100 degrees centigrade, where heating food is not the main function of the vessel, will be treated the same as vessels which are not for heating food.

The notification does not state the method by which these standards will be enforced, but department stores in particular are asking for certification of safety in Japanese before vessels can be sold. This is probably in line with the Public Liability Laws which were introduced a few years ago making the manufacturer and retailer responsible for injury to customers due to faulty or dangerous products. I believe that it is required by customs for imported ware, and as I was required to provide this for Mitsukoshi, and my pots are made in Japan, it seems to be required for domestic sales as well. I have only been asked by department stores, however, so I am unsure of the extent to which certification is required.

It only applies to vessels for food. In particular it is important with low fired lead glazes and on glaze enamels, but it applies to all food vessels. Within Japan testing can be done in a variety of places, but I recommend the Tajimi Ceramic Institute. Their home page outlines their testing methods and costs. One representative sample of work should be sent for testing, and they return it. I do not know whether they accept work for testing from overseas.

So, there you have it. If you are making vessels for food, Japanese law requires that they be food safe according to ISO standards. That sounds fair to me.

Black is Black

My friend and fellow deshi of Shimaoka sensei asked me an interesting question the other day.



"How do you keep your black glaze black in a Soda Firing?"



There are indeed lots of ways of getting a black glaze, but you have to decide what kind of black you want. Many black glazes use an overcharge of several colouring oxides to give a dense black. In my case, I am looking for the warm translucency one finds in lacquer ware. Lacquer is in fact brown, but layer upon layer make it so dense it appears black.





In order to achieve a similar brown based black I turned to the Tenmoku style iron glaze. The base glaze is clear, using only four ingredients; Feldspar, Silica, Whiting, Kaolin. To this I add FeO, or Black Iron Oxide.



Using Black Iron Oxide gives you a head start, as the Iron is already reduced. Using Red Iron Oxide, Fe2O3, will require more work to get rid of the unnecessary oxygen.



There are a plethora of glaze recipes available which are excellent Tenmoku in a gas kiln.


Within any plant there are minerals which have been drawn from the ground, and when burnt these minerals either become gaseous and volatise off into the atmosphere or remain as a solid residue, ash. When firing a wood kiln the gaseous minerals, like sodium, will flow through the kiln with the flame and exhaust gases, combining where it contacts with free silica in the clay or glaze surface to form a soda glass glaze. Ash is blown into the kiln with the flame as a powder, settling on the pottery and glaze, adding a coating of a variety of minerals depending on the plant. At a high enough temperature, usually about 1300 centigrade, these minerals, silica and fluxes, will melt and form a glass coating all on their own. The colour and surface will be affected also by what minerals are contained in the vessel surface and mix into the glaze matrix. At the end of my wood firing I also add some Soda Ash , NaCO3, which becomes a gaseous flux inside the kiln in the same way as the natural vapours from the wood.


So, in a wood and soda firing the glaze gets watered down. The ash adds an extra wash of relatively clear glaze and the gaseous flux Sodium makes the glaze melt even more. You end up with a variety of oatmeal and honey glazes. You can see how the "hidasuki" markings from the "Igusa" straw have left golden veins in the black glaze on this plate. Too much straw and it all turns to golden toffee. That can be nice, but it's not black, and it might not be what you want.



So, you need to make the glaze harder, so that it is a bit short of flux and a bit resistant to soda, raising its melting point. By reducing the Feldspar, for example, it raises the melting point, but also raises the ratio of Iron in the glaze. Iron is resistant to soda. Effectively you adjust the glaze recipe to make allowance for the extra flux which is floating around as a gas in the kiln atmosphere.


Glaze application is also important, as no matter how good your glaze is, if it is too thin the ash and soda are going to win. I apply my glaze at a viscosity of 60 by the hydrometer. Tenmoku is very sensitive to variations in texture underneath, so also be aware that the finished glaze surface and colour are only as good as the finished surface of the vessel.

It has taken me years to get my clay body, glaze recipe, glaze application and firing right, and all of those variables affect the finished result. The same glaze will be different in a different firing or on different clay, so it is necessary to experiment with your own materials and firing. In the end it becomes another inimitable expression of your own aesthetic. Hopefully these principles will help you along the way.

A Course in Basics

It is no accident that there is a similarity in form between thrown cylindrical pots and the structure of bamboo. Though they are not "Copies" of bamboo, a cylinder is a cylinder, and man made forms will naturally have commonalities with natural forms.









When learning to throw on the potters wheel the most basic skill one must master is the making of cylinders. All other forms thrown off the wheel head are based on this form. So, step one; Make one hundred cylinders.










It is important that they be accurate in size. These pots are 300 grams each, so if the weight of the clay is the same, and the height and diameter are the same, the wall thickness will also be the same. By turning the foot in a curve from the hip to a foot ring slightly smaller in diameter than the inside of the lip, the pots can be stacked for easy storage in the home or restaurant. The external rim measurement for these cylinders needs to be 72mm when fired, so allowance is made for shrinkage, which in my clay is exactly 10%, so the wet measurement was 80mm.
　　
　　
　　

And what are they for?

　　

　　

　　

They are lidded containers for another course of the Toyoda "Euan" menu which starts on September 30th. The lids are lacquer ware, and the pots are made to fit the lids, thus the diameter of the rim is vital. After 30 years of throwing, I still take great joy in making these simple forms. It reminds me that the key to mastering advanced skills is essentially the mastery of basic skills, of course.

Safety First

I have always made it a point to use only natural and safe materials when producing my work. There are no toxic materials in my clay, glazes or firing process. No Lead, No Barium, nothing toxic. Particularly considering that my studio is next to my children's bedroom!

I am careful to reduce dust and use a dust mask wherever necessary (special thanks to Phil Rogers for sending me a Dust Mask from the UK that didn't bend my nose over like the Japanese ones do!), and I use eye and ear protection where appropriate.

I have therefore always known that my products were safe for the consumer. This has always been a primary concern for me.

However, in order to sell my work at Mitsukoshi Department store I had to have my work tested by a public authority to prove it was safe for use with food. This is now necessary for all ceramics imported into Japan, and will apparently become standard practice by law for local production as well in the near future.

So, I sent my work to the Tajimi Ceramic Institute for testing and received this certificate proving that my work is perfectly safe for use with food. You no longer have to take my word for it!

Countdown

It is only seven weeks till my next major event. Mitsukoshi department store has invited my to exhibit at their main store in Nihombashi from September 30th till October 20th. Coinciding with the exhibition, Kappo Toyoda will be serving a special "Euan" course in their evening menu. After having discussions with Hashimoto san, the chef, I produced a range of prototypes which we then used in a photo shoot on saturday last.

The results were amazing, and I can hardly wait to share them with you. However, let us not get carried away. I am going to show then to you one course/one vessel at a time, as I make them. You see, even though we've done the photo shoot, only the prototypes are finished. The actual pots for the meal (20 place settings) and the exhibition (enough to last three weeks in the premiere department store in Japan) are yet to be completed!

This week I focused on square plates. I have purposely placed these at the fire face to get heavy ash and soda deposits. On its own the plate seems a bit lonely, but that is because it was designed to hold food, therefore without food it is incomplete.

Once the food is served, however, it comes to life.

These plates are first thrown on the wheel with 1.2kg of clay as a wide rimmed 24cm dish. After they are trimmed I will cut them square. I threw 80 of them today, and, with the other 200 pieces I made this week, my shelves are full.

Being summer the humidity is high, so I will have to wait for a few days before I can continue. Which is fine, because the kids are on school holidays and they need me too.

Opening the Box

No matter how cleverly you stack the kiln, or how well you have mastered the firing, the fact remains that the results from a wood kiln are in the hands of nature. You will never know for sure how the pots will come out until they do, actually, come out. It is a matter of faith, of trusting the process of nature. And if you have guided the firing well, the kiln will reward you with exceptional pots, far beyond the limits of your own ability.







My firing on Saturday took 13 hours, so it was fairly fast, but I gave it a very heavy reduction, including a reduced cooling. When I opened the kiln this morning I was surprised by a slightly metallic lustre on the surface of flashing and blue clouding in the black glaze. The pink spot on the rim of the plate is porcelain slip with 2% of Copper Oxide, so it is a good indication of the heavy reduction. In oxidation it would be green. The green slip trailing is also porcelain, but with 2% Chrome.






There was also more orange flashing towards the fire face than usual, which will balance with the heavy carbon trapping from the previous firing when I display them together at my next exhibition.










There were more losses than I've had recently, but that is mainly because of the large number of plates with the black glaze. Just one grain of sand or flake of kiln wash will ruin the whole piece.










Two hundred of the pieces from this firing will be going into my next exhibition and will be available for purchase at New York Takashimaya Home, 10F Takashimaya Department Store, Shinjuku, Tokyo, from next Wednesday, July 15th till July 28th.
I will be at the exhibition on the 15th, 18th, 19th, 25th, 26th, 27th and 28th, if you would like to visit while I am there.

How I Stack My Kiln

There are many people who have now built my kiln, and everyone will stack and fire it differently in order to achieve their desired result. Just for the record though, I wanted to show you how I stack my kiln and why.

Firstly, The brick arrangement under the shelves is designed to force the flame to the front of the kiln. The surface area of the space between the bricks is equal to the surface area of the flame inlet mouths at the back of the kiln which also equals the exit flue in the floor off the kiln. That means that the same amount of flame can come into the kiln, find its way through the work and exit the kiln. draft can then be controlled by the damper and the stoking volume and rate.




The first layer of shelves goes onto the bag wall right up to the fire face. There is a coil of wadding along the bag wall to stop the draft going straight under the first shelf. It forces the flame to go up first without taking short cuts.









There is a gap of 13cm on either side of the shelves. The pots can overhang this gap as much as you like, it won't affect the firing. You will notice how crusty the kiln is; that's because I've fired it 120 times over the last 10 years.









Between the shelves I leave 1.5cm of space only, this is part of the total exit space calculation.












It is important to stack this kiln tight. How tight? Tight as a salmons sphincter should do it. I only leave one or two milimetres of space between pots. Firing raw means the pots will shrink away from each other anyway, but it is also important to stack as tight as possible because the kiln is built of insulating brick and doesn't store a heat mass, so the work must become the heat mass.





I try to get as many pots as possible into the kiln. These cups have no glaze on them at all, I am relying on the wood effects to glaze them for me, the best place for them is at the fire face. Glazed work should be stacked at the front of the kiln away from the direct flame.









The handles force me to leave more space above the pots than I would like. Ideally the space should be about 1cm.











I stack right up to the arch, keeping it as tight as possible. There is plenty of space between the pots for the flame to get through, and as it does it leaves ash and vapour flashing. If there is too much space around, above or between the pots, the flame will rush straight past the pots and up the chimney, taking all its ash and vapour with it.







The front shelves go in with the same 1.5cm gap.
A long brick bridges the gap over the flue.

The front stack is also stacked tightly, with work that I would prefer less ash on, like the black glaze, or pots that I want more red or orange flashing rather than ash deposit.

This firing only used 40 kiln shelves, but the maximum I have used is 80, all plates. The tighter it is stacked, the better. It usually holds about 400 pieces per firing.