Crowan Pottery pin tray (7cm diam)

 

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Phil Oliver

25 July 2011

 

 

             The Potters Alternative

 

 

Click to see more details of the book

Harry Davis published a book in the later years of his life.  This is not an autobiography, but is aimed at potters who would like to be more self-reliant with raw materials, tools and machines.

The original version is well out of print, but Gentle Breeze Publishing have re-published it as part of their 'Pottery Classic Brought Back' series.

ISBN NO 1 889250 34 1

Copies are available from AXNER OnLine

Although most of the book is very technical the following two extracts are of more general interest.

Introduction

This gives a good indication of how Harry Davis viewed the Studio Pottery movement, as 'led' by Bernard Leach. Although he used the design style he formed at the Leach Pottery for the rest of his working life, he had no time for the artistic 'posing' that went on there.
 

Glazes and Pigments

This gives an idea of the materials he used to achieve the very distinctive glazes and colours of Crowan and Crewenna pots.


Introduction (Part of)

Handcraft methods, whatever the craft, involve material limitations and handicaps, which craftspeople, especially potters, need to face and seek compensations for. These handicaps and limitations are willingly and gladly accepted, and this I heartily endorse. It is quite another matter, however, to do nothing about the economic disadvantages that result from this. It is with this thought in mind that I have written The Potter's Alternative.

The nature of pots as receptacles, and the need for such things in everyone's daily life, has always made the potter a valuable member of the community. This is the basic practical side of the potter's role. The other side rejoices in the fact that through the centuries, potters took sufficient pride and joy in their job to make pots a medium of creative expression. In short, the things they made gave their customers not just something to put things in or on, but also an element of spiritual sustenance as well. Potters thus enriched the ordinary domestic life on two planes. The term 'artist' never entered the vocabulary of many generations of potters prior to the industrial revolution, but they were artists in the best sense - the unselfconscious sense. They were important practical citizens as well.

In my lifetime, potters of the revivalist handcraft movement conceived the idea of jumping on the 'fine art' bandwagon. This absolved them from their obligations in practical terms, and changed almost everything about what would be expected of them henceforth. It meant a change of social status and, above all, a big change in the attitude to pricing. In other words, just like their predecessor of two centuries earlier, Josiah Wedgewood, the potters had to ingratiate themselves with an upper class and affluent elite, thus pricing their pots well beyond the reach of the common people. All sorts of terminology had to undergo a change as well. An apprentice was renamed a 'student'. Pots were no longer sold in a shop but in a 'gallery' and the potter's place of work had to become a 'studio'.

The initiators of the new movement were middle class and unfamiliar with the demands of the practical side of life. They were educated in Latin, Greek and literature and perhaps in history, but not in simple, practical mechanics. They typified one half of C.P. Snow's idea of a divided culture. Like the men from previous generations, Rousseau, Ruskin and Blake (who doubtless influenced their thinking), they detested machines. But unlike Lewis Mumford, their grasp of history had failed to teach them that some machines were benign tools, and that the great coercive 'mega-machine' was what should have been the object of their ire.

When I left England in 1937, engaged by the Crown Agents for the Colonies to train some of the local West Africans as potters, I came in for a very rude awakening. Until then, I had been unaware of the abysmal ignorance on practical matters of my peers and mentors in the handcraft movement. Their ability and willingness to shelter under the 'art' canopy had relieved us all of the need to grapple with practical and technological issues, and had led in most cases to deplorable levels of skill. In some cases it led to a veritable worshipping of 'unskill', so that the split between the practical and the creative had become almost total.

With the rapid growth of the craft movement and the spread of craft teaching in more and more art schools and colleges, this split was reinforced and perpetuated, and the basic and practical side of pottery was farmed out to supply companies. This led to further increases in prices. Something which began with William Morris as a protest at the all-pervading materialism of the 'establishment' and its industrial wing, had come full circle and become just another facet of it and the consumer society....

The Glazes and Pigments used by Harry Davis

The character of glazes made up from igneous rocks is decided very much by the accessory minerals that happen to be present. There are two such minerals which can be removed. Magnetite is one. The other is mica. This came as a surprise to me when I began to make glazes from a rather dark granite from the Redruth area in Cornwall. It turned out that mica is very resistant to crushing and grinding and, in this case, the black mica contained in the granite seemed to be almost unaffected by some four hours of milling. It was possible to remove it almost entirely by passing the glaze through a 120 mesh sieve and the result was one of the most attractive celadon glazes of that period. Muscovite (white mica) is similarly resistant but there is no point in removing it as it is colourless and has a chemical composition very close to orthoclase feldspar. Furthermore the platelike texture of mica contributes very pleasant qualities to the surface of a glaze in the unfired state which makes it very nice for brush decorating, whether in pigment or wax. In my opinion mica also improves the feel of a clay for throwing.

The colour of celadon green glazes can be a good indicator of iron content in materials if fired in a reducing atmosphere. They should, of course, be applied to either a light-coloured stoneware or a porcelain body. The colour relates to iron content in approximately the following manner:


 
0.5% and less of iron (Fe2O3)
1-1.5% of iron
2-2.5% of iron
5-10% of iron
= delicate blues
= light greens
= olive greens
= blacks

This presupposes little or no magnesium oxide (MgO) content, and a calcium carbonate (CaCO3) equivalent in the order of 10 to 15 per cent.

Tourmaline granites are another instance where glaze character is governed by accessory minerals. Such granites occur in Cornwall in several places and I worked on them at one stage. Tourmaline is defined as a borosilicate. This small boron content gave a decided character to the glazes made from that granite. It also lowered the melting point.

My interest in granites as a glaze material began in West Africa in 1937. Then I reasoned that any of the acid or intermediate igneous rocks would only need additions of quartz or calcium carbonate to yield workable glazes. This turned out to be a most fruitful idea. Viewed with a magnifying glass such a rock specimen can be readily seen to have a high, low or zero quartz content, so that any necessary additions become obvious.

A mix of 80 per cent granite, 10 per cent calcium carbonate and 10 per cent clay became a basic theme in testing acid and intermediate type rocks and turned out to be something of a magic formula. Most attractive glazes often resulted without even the need to make adjustments to the quartz and calcium carbonate.

This occurred no matter where I happened to be working. I have used this 8:1:1 formula, as it came to be called, in many countries and different continents with most gratifying results. The fact is, rocks of those types and their derivatives are spread around our planet very liberally. There is scope for many other variations, especially with magnesium-bearing materials. Twenty per cent of dolomite in place of the 10 per cent of carbonate is an example which brings the rock content down to 70 per cent.
Much the same result will be achieved by adding 10 per cent of steatite without changing the carbonate content. Rocks rich in MgO, like serpentine, from among the more basic rocks, can also be used with interesting results. In fact all the basic rocks can be added in small amounts, but the tendency is to end up with only variations in brown.

Rocks low, or even free of iron-bearing minerals are comparatively rare. Pegmatite (a very coarse granite) and Cornish stone are examples. Cornish stone is an unusual rock related to granite which belongs in a borderline position between the acid and the intermediate. Nepheline syenite is an intermediate type of rock which is quite commonly found with iron-bearing minerals, and only very rarely without them. Even in a unique Canadian instance iron is present in the form of magnetite, but this yields to magnetic separation. These rocks can be treated in the same way using the 8:1:1 formula basing the mixture on the visible presence of free silica or its absence. These are the materials necessary if one is seeking white or colourless glazes, and also for those delicate blue and green celadon effects. For success in this respect the glazes must be applied to equally iron-free clays or to porcelain.

A total absence of iron in materials is almost unheard of, but in any case small amounts of iron are an asset when pots are fired in reducing conditions. That way an illusion of whiteness is created - just like the practice of putting 'blue' in the washing!



 

Pigments and Oxides

My personal prejudice in favour of simplicity and independence, and my preference for a reliance on local resources, are the reasons why I have limited myself almost solely to iron oxide as a colouring agent.

This is a universally common material and with a ball mill, even a small one, it is easy and cheap to obtain.

A great deal can also be done with it and the range of tones and colours possible with iron oxide alone is really astonishing.

It offers a range of yellows through ochre to reds, and another range of delicate blues through light to dark greens and black.

The iron minerals, hematite and limonite, are very common and can turn up as veins or pockets in clays and rocks almost anywhere.


A lidded jug showing some of the colours
possible using iron oxide

 Even if these are not in evidence, the recent human mastery of iron and steel has caused artificial deposits of iron oxide to appear around the world. It is known as common rust. Abandoned steel scrap will yield quantities of rust flakes if beaten with a hammer. I have known well established scrapyards where rust lies inches deep on the ground and can be literally shovelled up. On one occasion I swept up 20 Ibs (9 kg) of rust flakes off the deck of a truck that had just delivered several tonnes of used steel girders. The most spectacular example I ever came across was at the base of a disused penstock pipe which had belonged to a hydroelectric plant. The power house had been removed and the pipe end was open. Apparently flood water occasionally came down the pipe depositing rust flakes at the bottom and there, to my amazement, was something like a tonne of it for the taking.

The way to prepare these sources of iron oxide depends on how they are to be used. In a case where a percentage of iron is to be added to a glaze, this is best done before the glaze is milled, and can be added as rust flakes or as ground hematite or limonite fine enough to pass a 6 mm sieve. If the intention is to use these materials with a brush for decorating, then they should be ground somewhat finer and calcined (fired) in open bowls at about 900 C. The result will be red oxide which needs further treatment in a ball mill to bring it to 200 mesh fineness. It is possible that hematite would yield this end product without the calcining, but my experience has been that hematite and limonite tend to occur together, and the limonite being a hydrous (claylike) material, does not lend itself to brush decorating unless it is calcined.

Cobalt is the only other colouring agent I have used.

I have three times come upon it where it could be had for the taking, but have done so only once. This was in Cornwall and the one visit to the site yielded enough cobalt to last a small pottery for generations of potters.

 The mineral in question was a cobalt arsenate called erethrine.

Cobalt calls for very fine grinding.


Crowan bottles with cobalt decoration  

The kind of reliance on local resources I have practiced has been in some measure my luck in the areas I have chosen to work in. Ghana, Cornwall, Nelson (New Zealand) and Peru have all been places rich in ceramic raw materials, but only in Nelson was the area chosen because of this. Obviously, there are parts of the world where the local resources are not adequate for a potter's needs, and things must be brought from afar. This applies to other aspects of a quest for independence, such as materials to build processing equipment.

Total independence is an impossibility and socially not something to be desired. In essence this is simply a case of either choosing what economic advantages a locality offers, or submitting uncritically to dependence on a system that benefits outside business interests. The former takes will and energy but has its rewards.

Harry Davis
The Potter's Alternative

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Harry Davis jar made at Crewenna c.1970