Avoncroft Pottery 1958

It is just over three years since Avoncroft Pottery moved to its new home, bringing its name with it. We had really outgrown our original premises, some seven miles away. Also it was not a good place to attract visitors, and we did not feel very secure there. Our new buildings, grouped round an open yard; which serves usefully as a car park, and the house in which I live were once the workshops and agent's house respectively of a country estate.

We brought all the equipment from the old pottery with us; all, that is, except the kiln. This was a two-firemouth, updraught which I had built originally for slipware. But in it I had been firing high-temperature stoneware for several years, and it wanted relining anyway. So, in some sadness, we pulled the thing down, salvaging the best bricks, which are now in the foundations of the new kiln. Thus we felt that we were taking some of our roots with us; and we hoped it might augur well for the future.

We had not any great quantity of stock to keep us going while setting up shop; so we had to hurry if we were not to starve or lose existing contacts. Soon concrete had been laid in the workshop and the wheels emplaced. We built benches and tables of large, pre-cast paving stones laid on brick piers - a most useful and cheap form of construction in a pottery. A garage across the yard was fitted out as a showroom. This we share with a well-known wrought-iron smith, Alan Knight, whose workshop is adjacent. To have two crafts going on alongside each other is a double attraction for visitors, and to some extent one kind of work sells the other.

The big task facing us was the new kiln. This had been designed, inch-scale working drawings made and planning permission obtained before we moved. I had decided on a two-chamber, climbing kiln on the principle of that at St. Ives, but differing in detail; also that, as in the old pottery, I would save workshop space by building it outside, merely roofing it over; but this roof has not materialised yet! The foundations involved the removal of some twenty-five tons of soil, all being done manually, and the laying of six tons of concrete, for which we were fortunate to have the use of a mechanical mixer. I decided to build the kiln in two phases. First the foundations, firemouths, chamber I and the chimney, by which time it seemed likely our stock of pots would be exhausted and it would be high time to get more made, fired and sold: then to add chamber II later at our convenience, but before the existing structure had had time to get out of shape. This all panned out very well and, working alone except for odd mortar mixing, I had phase one completed in three months. Work was not continuous because time was set apart most days for making pots ready to be fired when the kiln was finished. Also we were held up at times by the weather, both wet and frosty. But a floodlight was rigged and on fine nights work was able to proceed far into the dark. By the following March we had fired - fairly successfully for a new and strange kiln. Then again in three weeks, and we were in production again. A few months later chamber II was added, the work taking a month to complete.

For those who wish to know more of this kiln, each chamber measures approximately 5' high, 4' 8" wide and 3' 6" deep, and the floor of chamber II is 15" above that of chamber I. For a long time I had considered oil firing, either by carburation or drip-feed. But, when the time came, I was not well placed to stand the initial cost of an oil burner and its attendant equipment; and as regards drip-feed, I had yet to be convinced that this method was sufficiently reliable for use at high temperature on a workshop scale as opposed to a studio scale (if I may make a subtle but important distinction). In any case, I had had a lot of experience with coal and wood firing; and, although the method is strenuous, used skilfully, it is both cheap and efficient. There is also a certain romantic element about it. Firings never quite become routine, which is a good thing in creative craft pottery. It is also exciting. The incandescent fires and flying sparks, the drumming, beating vibration of the draught through narrow flues when the temperature gets up; and the occasional "flash-over" by night from the top of the chimney after a stoke which has been enthusiastic rather than economical. Such things have real meaning for me and are more than just incidentals. But, then, I am and always have been a pyromantic! I have many times lost my eyebrows and forelock with solid fuel kilns, and once even had myself mildly on fire: but I would not lightly exchange the heat and toil for the dial reading and knob twiddling of modern "efficient" methods. One summer night we fired through a violent thunderstorm. The yard flooded and began to discharge its load into the firing well, threatening to drown all the fuel. Two assistants managed to keep me bailed out while, splashing about, I continued to fire. Then all the lights went out. We were nearing the peak temperature. Down came the rain and straight up again it went as steam. The whole atmosphere was an inferno of bursts of flame and sparks, black smoke, steam, the crash of thunder, the crackle of blazing wood, the cut and flicker of lightning and the roar of hail on the temporary tin roof. It was a dramatic scene indeed. What a night! Yet somehow we enjoyed the holocaust and it was a very good firing.

So the firemouths were designed for solid fuel. There are two, side by side, the better to heat the width of the kiln. The total grate area is five square feet. Both fires discharge through wide, arched flues into a transverse throat extending the whole width of chamber, and eight inches deep. Seven flues of lintel construction lead through the bottom of the rear wall of chamber I to another transverse flue the width of chamber II. From this point several flues extend below the floor of the chamber as a by-pass to the chimney. These gather into two ducts before entering the stack, each separately dampered. Six flues lead from the back of chamber II to the chimney and each of these is independently dampered. Thus, whether or not the by-pass is in use, the fire can be pulled with remarkable effect from one side of the kiln to the other. This, with the provision for stoking each side of the kiln independently, makes for flexibility and is capable of nice adjustment. The by-pass arrangement, which involved a good deal of complex building, has fully justified itself; for if the firing of chamber I becomes protracted, chamber II rises beyond the requirements of our biscuit. There is also provision for side-stoking chamber II with wood when it is wanted for glaze. I much want to try this out, but it has not yet been convenient to the general working programme. very As regards materials, in the very hot spots which also carry a structural load, we have used Morgan Refractories' MR1 bricks. These, in my experience, are beyond criticism. The next hottest places, including the fireboxes, were built of Pearson's Alite D bricks, which are proving very good. The kiln chambers are double-skinned. The hot faces are 41" thick and made of Pearson's "p" bricks washed with liquid Peer "M" cement from the same firm. After three years' use, there is absolutely no sign of "dropper" formation. Between the hot face and the outer wall is a one inch cavity filled with finely sifted ash. The outer wall, since it has to contend with the weather, consists of a 41" thickness of red engineering bricks. These are rejects from oxidised areas of blue brick kilns. They are vitreous or semi-vitreous, dark purple red or red in colour, very strong weather resistant. The chimney, 15' 6" high and 9" thick throughout, tapers towards the top and is lined with firebrick for two thirds of its height. There is a large air damper at the base.

There will be a good deal of tongue clicking, I fancy, from thermal efficiency experts about this form of construction. We use grade III or IV coal and we have to buy wood, which is not cheap: yet the cost of fuel per pot for a double firing (i.e., biscuit to 900⁰C., plus glaze to 1,300⁰C. average) is rather less than 23d. The experts are right in principle, of course, but wholesale use of high temperature insulation bricks would have doubled the cost of the kiln, which was exactly £150 in materials. Working on our scale, when the kiln is only fired ten or twelve times a year, it is more convenient to spend a few shillings more in fuel than to face a large initial expenditure on expensive insulating materials. Of course the design of the kiln, the fuel and the skill with which it is used count for a great deal. Even so, it is a point of view I would recommend to the attention of prospective kiln builders if they have so far listened only to the economies of heat utilisation experts.

For our body we have for years used Messrs. Potclays' buff clay, to which we add 5% grog and 5% fine red sand, both sieved 40s. to dust, making 10% roughage in all. For larger pots we increase the size of this; and for a darker body add some red clay as well.

Four glazes are in regular use for standard ware. A celadon, a rather shiny feldspar, china clay and ash glaze; a plum coloured khaki and a wood-ash glaze approximating to Miss Pleydell-Bouverie's classic formula. We produce a Tenmoku by double glazing first in the khaki glaze, then in the wood ash glaze. The success of this depends upon exactly the right thickness of the top glaze relative to the lower one. There are some half a dozen other glazes which are used on individual pots. All the usual stoneware decorating methods are in use and we do a great deal of double glazing, often with a combed finger pattern through the first glaze while still wet.

Basic production is of standard repetition shapes for which there is a catalogue. I believe that hand potters should face up to the problem of supplying well made, usable pots at a reasonable price. In that way they can make a better contribution to society as a whole. I have always viewed with suspicion the over-"studio" approach with its undue emphasis on individuality and orignality - concepts which materialise so often and so sadly as mere novelty. Moreover, it caters for too shallow a stratum of the community. Apart from this, repetition production, provided it is not carried too far, engenders a self discipline in workmanship and a humility towards clay which I doubt can be acquired in any other manner. It is also the only way of gaining real insight into form. No potter who has thrown a shape to the same superficial measurements, many hundreds of times, over a period of years and has seen that shape change, either voluntarily or involuntarily, will fail to understand this.

In addition each kiln contains its quota of individual pots, whose purpose is chiefly to probe fresh ground, or to re-test by repetition or variation, the validity of accepted ideas. This counterpoint of repetition and individuality is, I think, a healthy arrangement. The making of standard ware is prevented from becoming dull, whilst individual pots are made on a basis of realities and the discipline and technique implicit in repetition work.

Firings usually take place once in a month or six weeks. The usual duration is twenty two hours. It used to be less, and we have done it in sixteen. But the best is not got out of glazes by hurrying, which, in a reduced firing, often invites other evils such as bloating. Kiln setting takes two days and saggars are used throughout, with intermittent wads to allow the flames to percolate. The use of open shelves, which would increase the setting space and theoretically, at any rate decrease fuel consumption, is not a good proposition with coal fired kilns. The pots tend to become coated with fine cinder and the glazes become discoloured and opaque unless they are situated right away from flame passages.

The fires are lit about 8 am and a slow smoking is kept up for about two hours, when some increase is made. An hour later the fire is gradually spread over the whole area of the bars and increased, keeping the atmosphere as oxidised as possible, though this is difficult at low temperature in such a kiln. As soon as the mean temperature has risen to 1,000⁰C, the kiln is thoroughly "washed" in an oxidising atmosphere to burn up any carbonaceous matter in the clay body and elsewhere. Then reduction proper begins. Until now the dampers have been wide open. They are now adjusted to create more pressure in the chamber. As in most kilns, the maximum pressure occurs at the crown of the chamber and decreases progressively downwards. If the kiln is to be worked efficiently and even heating maintained, and particularly if uniform reduction is to take place, the pressure must be adjusted so that it is just positive at the lowest level of the setting space: that is to say when flame and gases will billow lazily out if a loose brick is removed at the bottom of the chamber. Over dampering will obstruct draught and unduly prolong firing. Even so, as the temperature of the kiln rises more and more, the draught increases and negative pressure may again occur at the bottom of the kiln, requiring yet more damper to counteract it.

Between ten o'clock and twelve midnight, cones 1A in all parts of the chamber should have squatted, and when the mean temperature has risen to about 1,150⁰C (the hottest zone then being over 1,200 and the coolest about 1,100) it is time to start stoking with wood. This wood consists of small billets of split pine. We burn it, however, on a bed of coal, as we find that a pure wood fire becomes flimsy after a time. Each bed of coal quite shallow and made up of fist sized lumps lasts for about six wood stokings, when it is replaced and followed by further baitings of wood. The kiln atmosphere becomes a rhythmic alternation of reduction and oxidation as each batch of fuel burns to ember. Care has to be taken that the oxidising period of each stoking cycle shall not be so long as to predominate and therefore determine the prevailing kiln atmosphere.

It is from 1,100⁰C to rather over 1,200 that this kiln seems to progress most slowly: but the slowness is more apparent than real. For one thing, we have no cones in the kiln to register any intermediate temperature, so that for a long time there is nothing to indicate material progress. For another, by this time fatigue is beginning to set in, and with it impatience. Because of this and enervation due to the heat, the whole performance seems to drag, and it is quite likely that a form of boredom may overtake the stoker. It must be sternly resisted, else the sense of continuity of what is going on inside the kiln will be lost. One cannot operate this sort of kiln by rule: only by feel, which is to say by merging oneself, as it were, with the fire and the materials of the pots. This may sound esoteric but is pretty near the truth. But for all the apparent delay, we have not experienced any definite or persistent sticking, as was sometimes the case at the old pottery. There we had to keep a stock of what came to be known as "crisis wood." This was carefully selected pine, absolutely dry and full of resin, set apart for use only in quite desperate circumstances.

The fall of cone 6A can be expected about three hours after the fall of cone 1A. Above about 1,230⁰C, the kiln has a tendency to accelerate without any change in the method of stoking. Great restraint is now called for. When one is very tired the temptation to rush the summit is great; but to do so invites flashed glazes, and it as well to take two more hours to the fall of cone 8. When cone 9 is down at the top of the chamber, the rhythm of stoking is changed. A frequent light application of wood is kept up, with the firedoors open, to create an oxidising atmosphere. By now, if not before, chamber II will have reached biscuit temperature and is cut out. This atmosphere is maintained for about an hour, to allow the glazes to settle and the unglazed parts to assume a warm brown colour. Curiously, there is much confusion about the kind of atmosphere which produces this colour. It has been written that it is due to oxidation; again, that reduction is the cause. Actually, it is a combination of both a long period of reduction followed by oxidation. The former brings the iron oxide in the body to a metallic state, making it fuse and concentrate to some extent on the surface. The subsequent oxidation restores the oxide in greater concentration and with more colour. A similar body given a strictly oxidised firing throughout will not acquire this colour; while a completely reduced firing, in which no oxygen, or very little, is allowed to enter the kiln after finishing, will leave the body grey.

There is a small additional increase of heat during this stage, until the final temperature in the hottest zone is about 1,350⁰C and in the coolest 1,250⁰C. This disparity, which the kiln was designed to provide, exactly fits the range of glazes harder or softer we use. Sometimes we fire a few pots, made with a semi-fireclay body and covered with rather refractory glazes, to over 1,400⁰C at the back of the firemouths.

When the final test rings have been withdrawn and vetted, the fires are allowed to burn right through. Then all dampers are closed to allow the kiln to soak under maximum available pressure for about ten minutes until cooling has obviously set in. At once both dampers and firemouths are opened wide to allow a continuous blast of cold air to sweep through, and the kiln is allowed to cool at high speed through about 400⁰C. This takes perhaps an hour and a half. Then dampers and firemouths are closed and the large air damper in the chimney base is opened to prevent any pull through the kiln. The firemouths are covered with bricks and lightly clammed up: but we make no fuss about sealing all fine cracks. I am not advocating such apparently casual behaviour as a general rule. It is just that, in our particular circumstances, it has proved unnecessary. Subsequent cooling takes only thirty six to forty hours as against three days otherwise. This is an advantage to one who, like myself, can never get at the drawing of a kiln fast enough; but the real reason for fast initial cooling is that it tends to eliminate body-glaze tensions, from which, at one time, we had a good deal of trouble in the form of shattering and spiral cracking. Evils of this nature, from which many stoneware potters have suffered at one time or another, are usually aggravated by the use of high-silica-content bodies.

The biscuit chamber is allowed to get quite cold before it is disturbed. At one time we had an unacceptable proportion of fine hair cracks in the biscuit, particularly in large pots. Very slow cooling failed to remove the trouble entirely. Now we fire chamber II to fully 900⁰C, to allow better sintering, and this has quite cured the trouble.

Cleaning up, pricing and sorting take about two days. We supply a number of retailers spread fairly evenly over the country. About a fifth of the output is sold in our shop on the premises, and we send to about half a dozen exhibitions a year, selling outright and taking orders. It seems best to get one's eggs into as many baskets as possible. We have several times turned down offers which, temporarily, would have been very remunerative, because their acceptance would seriously have curtailed normal work and probably would have lost us more lasting contacts.

We have had a fluctuating population at the pottery. My wife, who helps whenever two small daughters and a rather large garden permit, makes all our press moulded pots. Various assistants and students have worked here and, I think, have learned a good deal during their stay. We are grateful for the help they have given. Nevertheless, I have, for long periods run the pottery unaided, and I cannot agree with Miss Helen Pincombe that one alone cannot run standard lines in tableware. We have averaged five to six thousand pots a year, which does not seem bad considering the large amount of work that has to be done besides the actual making. It has meant hard work - when single handed about seventy hours a week and sometimes one naturally gets fatigued. But it is not work which makes a man tired so much as the attitude of mind he adopts towards it; and herein lies much of the significance of a craft as a "way of life."

There are no frills in this workshop, and students who come. here find (I think to their considerable advantage) that they have to make do with very simple equipment. We use kick wheels. I would have a power wheel only if I felt it would be justified. We have no clay making machinery. A pug mill would save labour but not much time, and so would not pay its way. However, such austerity, provided it is not taken too far, is wholly good in a craft such as ours, wherein simplicity and directness of approach have a value not easily recognised and assessed until much experience has been gained.

Of materials, we try to keep to very few. To have few, to know them really well and fully understand their capabilities brings breadth to one's work. Too many extras tend to cloud the issues and so have the opposite effect. One cannot hope to gain fluent mastery of all the possibilities in a wide variety of materials. Better stick to a few which work and really know them. Similarly with decoration. Although we have a variety of ways, I always feel happiest when I can exploit what the interaction of body, glaze and fire will produce naturally encouraged and heightened sometimes by fluting, engraving or the judicious cutting of facets on the pot. There is nothing new about this, of course, but it seems to me to be the best way of working in stoneware.

I hope eventually to build up a three or four man permanent team. Anything larger, it seems to me, would bring in its train problems of all sorts, and reduce the leader from a potter to a mere business manager. But the right personalities are very rare. In most whom one meets the fire does not really burn. Although we have never descended to the expedient of making only what we can sell, our turnover has increased steadily - if slowly - from the start; but we are now facing greater overheads, and it is not easy, without capital resources, to plunge into a regular weekly wage bill. That would require a quick and lasting leap in sales, and I do not need to tell other potters that this is difficult to arrange. For all that, I am an optimist about our future as useful members of society. But we must cater for that society in depth. I feel little sympathy for the potter sculptor for that is what he really is - in his studio. Make a proportion of individual, expensive pieces if you like; but the main effort should be directed towards bringing the delights of good, hand made pots within the reach of all. To that end this workshop will unceasingly strive.

Avoncroft Pottery plan