Pottery, unlike painting, does not depict landscape; it is the landscape. Through knowledge gained empirically or by the application of scientific theory, the earth beneath the potters feet is transformed into objects which may be both useful and beautiful. In Rock Glazes, Geology and Mineral Processing for Potters: A Personal Approach, Steve Harrison examines how the studio-potter may use clays, rocks and even the detritus of the built environment to create glazes that echo the land in a manner that is both literal and abstract.
For thousands of years, whether in the hands of village craftsmen or technocrats, these skills were an integral part of the practice of ceramics. Over time this knowledge was compartmentalised, hived off as the province of specialists. Whether within the manufactories of Stoke-on-Trent or in the traditional Chinese pottery centres of Longquan or Jingdezhen, the vast scale of production had led to a situation whereby those who made the pots were not the same people who made the clay, and the workers who made the glazes did not build or fire the kilns. Such is the nature of industry, an enterprise which, whilst not being without craftsmanship, is quite different to the crafts, at least as the term came to be understood in the twentieth century. Thanks to outspoken and persuasive commentators like Bernard Leach, the advent of this modern crafts movement brought with it the notion of the studio-potter, an artist-craftsperson who chose to creatively reinterpret traditional practices in a manner and on a scale more allied to the world of art than of industry. An integral part of this new model was the concept of 'truth to materials'. Whereas industry strove to make pottery that was ever whiter, finer and glossier, many within the crafts movement sought other directions, to the extent that the imperfections brought about by the use of unrefined materials were often celebrated within the studio pottery movement, coming to define no less than an alternate aesthetic paradigm.
Leach was the pivot around which this part of ceramic history turned. A Potter's Book, published in 1940, was the first generally available text (which is not to say it was the only one) for the studio-potter to deal comprehensively with how stoneware pottery could be made outside of an industrial setting. In his book, Leach gave detailed and practical guidance as to how common minerals - feldspar, limestone and quartz – could provide the backbone for high temperature glazes. In addition, drawing on his experience of North Asian traditions, he included other non-industrial materials, including wood ash and the Japanese kimaichi stone, in his glaze recipes. A Potter's Book contains analysis of these hitherto overlooked substances and explains how they may modify or replace more 'traditional' glaze ingredients. For the first time the studio potter was able to see how the ash from their fireplace (or, in those more lenient times, the backyard incinerator) contained many of the substances necessary to construct a workable stoneware glaze.  This was a radical departure from standard Western ceramic practice, but, in Leach's view, a potter might not only gain a degree of independence by working in this way, but it would imbue their work with an organic quality, setting it apart from industrial ware.  Philosophy and practice would meet, and be reconciled. The extent to which this approach was adopted, and how it may have benefited or constrained the ceramic arts, is still the subject of debate.
In Australia, many of the pioneers of studio pottery followed suit. Aided by Leach's book, the Melbourne potters Harold and Robert Hughan turned quickly from the idiom of earthenware to become amongst the very first exponents of high-fired studio-pottery.  Ivan Mc Meekin, who had worked with Michael Cardew in England, became obsessed with materials, a process which would culminate in his extraordinary text Notes for Potters in Australia, a treatise on Australian ceramic materials which remains unparalleled in its rigour. Ivan Englund began his exploration of rock glazes, and, from Eileen Keys in Western Australia to Carl McConnell in Queensland, potters turned to the ground to see what vigour was in its bones.
The use of 'natural' materials is fundamentally a stoneware technique, but in the early years kilns that could reliably reach stoneware temperatures were few and far between, with many an exciting – and risky – experiment carried out with dripping sump-oil and jerry-rigged blowers in sheds across the country. With a copy of A Potter's Book, or later Daniel Rhodes' excellent Clay and Glazes for the Potter near at hand, Australian potters covered their pots in simple mixtures of clay, ash, limestone, dolomite, feldspar and quartz, crossed their fingers and waited nervously for the results. 
With the advent of journals and books dedicated to Australian studio pottery, information gleaned from this experimental work became available, although, Australian publishing being what it is, the pace was somewhat leisurely.  It was in the pages of Pottery in Australia magazine that a meaningful dialogue began as to the nature of stoneware techniques, the clays, glazes and kilns germane to this exciting field of endeavour. Given the makeup of the editorial staff this was no surprise, and as early as the third issue (May 1963) Ivan Englund, who was then President of the Potters Society of New South Wales, the publishers of the magazine, authored an article 'The Bumbo Latite – a useful igneous rock for potters'. It is here that we find a template for all future contributions on the use of Australian rocks in stoneware glazes, and which, somewhat belatedly, serves as an introduction to a discussion of Harrison's book.
Not unnaturally, most treatises on the subject of rock glazes have several things in common, and Harrison's book is no exception. There is information on the chemical and physical nature of glazes, on the raw materials and how one might go about collecting them, and the all-important question of how the rocks are to be rendered into a state useful to the potter. This latter problem is addressed in two ways. One is to find a working quarry, make friends with the quarrymen and collect the fine dust from around the crushers. This is the easy way, recommended by Ivan Englund in his 1983 book on the subject, Rock Glazes.  The second option is to assemble a range of implements whereby several kilos of rocks may be turned into a powder fine enough to be suspended in a glaze solution. This is the hard way, though it brings its own rewards if you are prepared to spend the necessary time, effort and money and if you live far enough from neighbours to get away with the racket. Steve Harrison covers both options, but perhaps understandably given the complexity of the task (and also, I suspect, due to the fact that he just has a lot of fun doing it) it is the latter approach which is stressed.
Jaw crushers, hammer mills, roller mills, disc disintegrators and especially ball mills are discussed at length, together with useful detail to do with ball sizes, speed of grinding and the wonderfully termed 'angle of nip'. There is a revised version of his Thoroughly Modern Milling, first published in Pottery in Australia vol 15. no's 1 and 2 in 1976, which surely must be the last word on the subject. Furthermore – and this is where Harrison's book delves into hitherto unexplored regions – he outlines a method by which constituent minerals, for example feldspar and silica, may be separated from the parent rock through a combination of mechanical and chemical treatments. Given the chemicals and labour involved this procedure will not appeal to most potters, but it is a fascinating account and one which stresses his dedication to the cause. The remainder of the book addresses a variety of subjects, from testing procedures to glaze chemistry, in brief but informative terms, and one might wish to follow Harrison's advice – and footnotes – in assembling a more extensive library on differing aspects of glaze technology or mineralogical analysis. What Steve Harrison does is to concentrate on one specific facet of ceramic inquiry, whilst locating it within a general field, and he does it well.
What he does not do is delve into the philosophy behind his approach (which he terms a 'location specific event' ) for the stated reason that he has addressed this topic in his other writings. I found further explanation of his philosophy of 'locality' on the Legge Gallery website, and couldn't help comparing his arguments with those made by Ivan McMeekin in his Introduction to Notes for Potters in Australia. There, McMeekin states one of the primary reasons for writing his book was because
The inference being that Australian potters were somewhat disadvantaged in this respect, although, given that McMeekin's book was published in 1985, it is arguable that by then Australian potters had access to a truly vast range of materials, both local and imported. Nonetheless, his emphasis is on assembling knowledge for the sake of knowledge:
Fine sentiments indeed.
Harrison's arguments are couched in somewhat more trenchant terms, positing the use of 'local' materials as an antidote to globalisation and the resultant aesthetic sameness in contemporary work. He states that:
One might point out that the smudging of cultural boundaries is not always a bad thing. Ceramics, tailored specifically for foreign markets, have been produced in China and shipped around the world for a very long time and constitute some of the most beautiful wares in ceramic history, though the standard seems to have been slipping over the last few hundred years. Harrison's work itself is the result of a fortuitous smudging of cultural boundaries, stemming as it does from the Anglo-Oriental tradition. It is worth remembering that one of Leach's great ambitions was the bringing together of East and West; yet, whilst his transposition of Oriental stoneware techniques was highly influential in the West, the Japanese audience favoured his English slip-ware, 'born' – as Yanagi rather diplomatically put it – 'not made.'  Lastly, it is highly unlikely the monopoly of a global ceramic industry will be challenged by exhibiting $500 soup bowls in a gallery, no matter what their geological DNA. As a political theorist Harrison is less than convincing. Where he is very convincing is in his work and this is where one really sees the benefits of his theories of locality.
Where I am absolutely in agreement with Harrison is in the aesthetic possibilities made possible by the use of un-refined materials. If one favours the personality and individuality brought to a pot by the inclusion of a little quartz, mica or iron in the body, or delights in the unexpected qualities of glazes made with rock and ash, then there is nothing better than Harrison's approach. It also returns to the potter a freedom and confidence which only comes through hands-on experience, hopefully translating into work that exhibits similar qualities. Of course, it is up to the individual to decide just what is 'local' and any argument that rests too heavily on this concept will be difficult to sustain. After all, it is perfectly possible to live – as I do – within a short drive of quarries that supply primary and secondary clays, limestone and quartz, graded, milled and bagged, yet despite this proximity I doubt whether their use would fall within Harrison's definition of a 'location specific event'. What is interesting is his use of the analogy of a 'terroir', referring as it does to a complex interaction of place, product and tradition. Here, Harrison's ideals share more than a little with the burgeoning 'slow food' movement in Australia, as he indicates by comparing the use of local produce with local materials. Other similarities exist, for example the concept of 'food miles', or indeed the willingness of certain members of the public to pay a premium for an organic, hand-made product. As yet, there are no distinct appellations in Australian ceramics, but, given the history, I wouldn't be surprised if the area around Mittagong would be the first.
 Englund, I 'Introduction' Rock Glazes privately published Ivan Englund 1983, p. 2
 In the table of celadon glazes contained in A Potter's Book, Leach sets out two recipes side by side, 'Leach's Korean type' and 'Kawai's Korean type', noting
... these recipes ... have the same percentage of feldspar. The ash is equivalent to the limestone ... the silica in his reed ash is more opalescent than the quartz in mine, but there is a strong similarity.
And, apropos of rock glazes, in his section on iron glazes Leach gives the chemical analysis for kimaichi stone, noting that it is 'one of the natural rocks used in Japan, for kaki (glaze)...'
From 'A Potter's Book' by Leach, Bernard, first published 1940 by Faber and Faber. pages 158-175
 Leach's observations of the differences between the hand-made and the products of industry were complex and extensive. I use the term 'organic' as a kind of shorthand only.
 I make the distinction here between studio-pottery and industrial ware, as there certainly were existing potteries, working in a semi-industrial way but nonetheless relying heavily on hand production, who regularly saw at least some wares fired to stoneware temperatures. I have worked at one of these factories, and know from evidence of the old glaze formulae, used on pickling-jars and the like, that it would have needed at least cone 8 temperatures to form a usable glaze.
 Not all Australian potters chose the straight and narrow path. Bernard Sahm, despite working in England with Cardew, showed no great interest in utilising Australian materials in the recreation of classic oriental glazes, just as he showed no particular interest in recreating the pots themselves. Maria Gazzard returned from England more inspired by Nicholas Vergette, Lucie Rie and Hans Coper than the St. Ives school. Alex Leckie made stoneware, but it owed more to Vallauris than Cornwall, and even Colin Levy's and Les Blakebrough's early work showed a willingness to combine 'found' materials with a decidedly experimental approach to form. (see Pottery in Australia Vol 6 #2 etc). If David and Hermia Boyd's earthenware may be posited at one end of a spectrum with the Hughan's stoneware at the other (a dialectical construct that should not be taken as gospel) the reality is that most Australian potters worked somewhere in the middle. Despite the rhetoric, Australian potters showed a willingness to embrace a variety of styles and influences, and any reading of craft history which overlooks these nuances does a disservice to the field.
 Prior to the arrival of the magazine Pottery in Australia in 1962, the only book published by, and for, Australian potters (at least that I'm aware of) was I. Landale Beetson's 1949 A Potter's Notebook. In common with many books of its time, Beetson's emphasis was on the making of earthenware pottery, a technique which was within the technical capabilities of most schools and hobbyist potters, as well as being the mainstay of studio production at the time. She did, however, at least acknowledge the field of high temperature glazing, including three recipes for porcelain glazes in her book, one of which might be constructed from a simple combination of un-fritted materials. Interestingly, her recipe of feldspar 167, flint 108, whiting 70 and china clay 52, works out in percentage terms to be very close to the Leach 4,3,2,1, a tried and tested lime/alkali combination of great versatility and reliability.
 Rock Glazes, 1983, privately published by Ivan Englund. ISBN 0 9591764 0 3, see pages 39 and 40 Preparation of Rock Materials
 Notes for Potters in Australia, by McMeekin, Ivan published by New South Wales University Press in 1985. p.3
 ibid p.6
 from http://www.leggegallery.com/HARRISON/Harrison2004.html
 Yanagi, collected letters, quoted in 'Bernard Leach' St.Ives Artists, by de Waal, Edmund. Tate gallery publishing, ISBN 1 8547 227 0