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The Complete Guide to High-Fire Glazes : Glazing & Firing at Cone 10, by John Britt

The Complete Guide to High-Fire Glazes: Glazing & Firing at Cone 10, by John Britt

With hundreds of recipes for some of the most popular and enduring high-fire glazes used today, this reference will prove a boon to ceramicists who want to master this complex aspect of the art. Author John Britt, who recently served as Clay Coordinator at the respected Penland School of Crafts, has personally tested many of the recipes himself, and carefully reviews every one.

He offers a thorough examination of glaze materials, chemistry, and tools, and presents the basics of mixing, application, and firing procedures. There’s specific information on each type of glaze, including copper, iron, shino, salt/soda, crystalline, and more. An exhaustive index of subjects and a separate index of glaze recipes will help ceramicists find what they need, quickly and easily.


“When I got a copy of ‘High Fire Glazes,’ I couldn't believe the amount of information it contained. I wish it were in print 35 years ago when I started working in clay. It's a treasure house for anyone working or looking to work in high fire glazes. It even contains recipes and pictures of flashing and other slips for those of us who soda or salt fire.

“It charts various firing schedules for many of the glaze recipes shown as well as gives specific gravity for the glaze. I also like the side-by-side listing of various formulas and the way they are grouped according to type and color. The book is very under priced. The eye candy alone is worth the price.” --June Perry in Bakersville, North Carolina USA

“John Britt's ‘High Fire Glazes’ is so well thumbed that I now have a copy for the garage as well as one for the house. This is definitely not a cookbook. It's an incredible array of just about everything to know concerning high fire glazes, glazing, and firing.

“Britt's section on application of glazes offers pictures following the narrative on dipping, brushing, spraying, pouring, as well as information on the use of resists. His selection of pots from other potters is pure eye-candy! The green glazes section, as an example, includes Shaner's oribe and jars from Ben Owen III. Talk about to die for! He writes about copper greens, chrome greens, iron green, titanium green, nickel green ... and then we move on to blue glazes.

“John's book is indeed ‘The Complete Guide to High Fire Glazes’ and makes me right this minute want to go work with the yellows and ash. I know that will require a lifetime all by itself, but that's the joy of pottery, is it not?” --Joyce Lee in the Mojave Desert of California USA

"This book is the ceramics bible for high fire glazes. Well organized with beautiful photos, this book answers every question a person might have. The book contains hundreds of glazes with ample photos, a must have for any potter."--Sarah Dargan of Helena, Montana, USA

"Potters are largely known as a generous group. However, there are a few clay artists whose working methods are kept a closely guarded secret. If there were any secrets with regard to high fire ceramics, John Britt has shed light on a range of materials and processes that will help aspiring ceramists working in this challenging area. Some of the topics covered by Mr. Britt include raw materials, mixing, application, firing, and glaze recipes. The chart for limits and firing cycles are especially informative. In addition to the illustrations, I also appreciate the photographic images of the pottery and sculpture. They are well lit and in full color and provide an example of the glaze color and texture. I highly recommend 'The Complete Guide to High-Fire Glazes.' It is a must-read for potters." --Rafael Molina of Mansfield, Texas, USA

"This is the most beautiful and comprehensive book written to date on high-fire glazes. John Britt has literally filled the high fire information vacuum. This book covers everything that you might want to know about glazes and glazing from a very practical and operational standpoint ... the materials, the cones, the glaze application, the recipe, the firing, and reproducibility. Just as important, there are so many pictures of glazes on real pots as well as test tiles, all well labeled, for the visual learners (and aren't we all?!!!). This book is a major contribution toward demystifying high-fire glazing and glazes and will become the foundation for high fire ceramics, much as 'Mastering Cone 6 Glazes' and 'Glazes Cone 6' have become the guides for intermediate-temperature firing. This is the book for which I have been waiting ... I can't put it down! The only thing better would be John Britt in person." --Paulette Carr

"John Britt has done a superb job sharing his years of experience with successful high fire glazes. John not only provides recipes and pictures of successful glazes, but he gives detailed information on how best to fire them. The book is well organized and allows glazes to be found easily. The pictures of glazed pieces and test tiles are of high quality and give accurate representations of the glazes. I recommend this book especially to those of us ceramicists who are working with high fire glazes. Even if you are not working with high fire glazes, this book may change your mind."--Paul J. Joseph of Maumee, Ohio, USA

----------------- Review by Charles Moore of Sacramento, California, USA

Let me start by saying that this is truly a wonderful book, filled with valuable information, fine recipes, and inspiring photos. The book offers two “Forwards” by potters of international renown. Val Cushing says, “His firing section is the best I have seen and will help solve many of the problems all ceramists face. The compositional effects on glaze colors and textures are beautifully illustrated, making it easy to refer to the specific formulas [recipes] to see what makes them do what they do” (p. 6). Tom Buck, in his Forward, notes that Britt, “…keeps a sharp focus on his main target, namely, to provide you with a full range of glaze recipes, the best way to mix each type and then apply the glaze to a…pot, and what the results will likely be…if you fire the pot to cone 10 in a kiln atmosphere of your choice” (p. 7).

In the early parts of High-Fire Glazes (pp. 12-56), following his introduction, Britt introduces the nature of glazes and a very interesting chapter called “Materials, Oxides, Colorants, and Melt Tests” ( pp. 16-25). In this section, he looks at most of the oxides common to glaze composition and colorants. I would particularly note his safety warnings about Barium Oxide: “[K]eep in mind that it’s extremely toxic, especially as a carbonate powder, when it becomes an airborne health hazard during mixing, and certainly if it leaches from a fired glaze…. Barium glazes aren’t suitable for functional ware” (pp. 19-20). He says much the same for Manganese Dioxide; however, once fired, it loses its toxicity.

Britt offers very clear and solid chapters on mixing glazes, application, and measuring heat (pp. 26-40). There is much for the novice to learn here, but experienced potters probably should give this section a quick once-over.

Perhaps one of the most informative and even exciting chapters is “Kilns, Firing, and Safety.” Here I must agree with Val Cushing’s assessment: the section on firing, especially on reduction firing, is the best that I have seen (pp, 44-45). Though I am experienced in firing both oxidation and reduction kilns, Britt’s six “Firing Cycles” (called “Firing Cycle R1, R2, R3, O1, O2, S1) for reduction and oxidation firing clarify what actually happens in the kiln during the cycle. He begins with a brief description of each cycle. For example: “Firing Cycle R1 represents a heavy reduction atmosphere, from the earliest point at which most glazes begin the melt (cone 012) to the end of the firing period, including a natural cooling cycle.” The “O” cycles are oxidation cycles; O2 is “an oxidation cycle with glaze reduction at the peak of the firing temperature….” He goes on to explain the differences in heavy, medium, and light reduction. Perhaps of greatest value to me are Britt’s color coded graphs on pages 44-45, which clearly distinguish the uses of the various reduction and oxidation atmospheres.

I need to note that Britt has finally clarified for me the term “striking,” as in Firing Cycle S1: “The kiln is put into reduction after it has reached its peak temperature (cone 10) and has cooled to between 1300-1800·F (7-4-982·C). At this point the [gas] kiln is restarted and put into heavy reduction for a period lasting from one to several hours. The temperature is held steady (potters say “soaking”) reduction…. Striking can create copper-reds, lusters, and even cause the clay body to become gray” (p. 47). Following is a sub-section on understanding what happens to the clay and glaze at different temperatures--some very precise and useful information.

The chapter ends with safety cautions and includes a list of materials that are toxic and a discussion of safe practices (pp. 51-52).

The huge chapter called “Overview of Glaze Types,” which presents numerous glaze types (e.g., Iron, Copper, Crystalline, Single Fire, etc.), pp. 57-167, is the heart of the text.. To exemplify Britt’s work, let me take a closer look at just a few types of glazes. The section featuring iron as the coloring oxide presents a variety of glazes, each with several recipes and many illustrated by photographs of test tiles and pots: celadon, temmoku (often spelled “tenmoku”), iron saturate, tea dust, shino, and other iron-colored glazes. Quite arbitrarily and since I love iron-influenced glazes, I would select, under Britt’s Iron glazes, his Temmoku glazes, p. 70. He presents 10 recipes, each arrayed on a graph that lists the percentage of ingredients of the various glazes, e.g., Custer Feldspar, Silica, Whiting, etc., and the varying amounts and kinds of Iron: Red Iron Oxide, Yellow Iron Oxide, Yellow Ochre—each presented as a percentage of the glaze. The graph is particularly useful for a quick comparison of the glaze recipes.

Britt gives a brief history of temmoku, originally from a Province of Fujian in China; later the Japanese developed their own version of the glaze. “Today the term [temmoku] refers to an entire class of Chinese or Japanese black or brown ware, including temmoku, iron saturate, kaki, tessha, tea dust, and oil spot glazes” (p. 70). He offers mixing, application (to a thickness of 1/16 or 1/8 inches), and firing instructions—always clear and well illustrated.

When I showed Britt’s book to my potter friend and mentor Linnell Barnhart, she immediately bought her own copy of the book and began to use it. She selected Mark’s Temmoku, which contains 10% Red Iron Oxide. She decided to test the glaze by taking the RIO up to 15% and produce one of the most beautiful glazes, a micro-crystalline surface variegating from brown to deep auburns, with hints of black. When Linnell had some difficulty with measuring the specific gravity of her glaze, she emailed John Britt, who walked her through the process and made himself available to answer further questions. How many authors offer such service?

I would particularly recommend Britt’s work on the several types of Shino glazes (pp. 79-86), including three types of Carbon Trap Shinos, in the iron-influenced glaze section. Regarding carbon trapping, Britt says, “The addition of 3 to 17 percent soda ash is the defining feature of this type of shino glaze. Because soda ash is soluble, as water evaporates from the glaze coat, it deposits the soda ash on the surface of the pot as a white powder. The migration of soda to the surface of the pot creates the possibility for its distinctive carbon trapping…[In heavy reduction,] The melting soda ash will trap the carbon and produce a solid, spotted black or gray glaze surface” (p. 82).

Again, quite arbitrarily, I will select a glaze type simply called “Purple” (pp. 114-117). There are several sections devoted to colors; in addition to purple, there are sub-chapters on blue, black, and yellow. Britt opens the purple section by noting, “Not a lot of attention is paid to purple glazes, but they can be quite beautiful. Unlike many other colors, there is no single oxide that can produce purple; instead, it takes a combination of oxides.” After a general overview of purple glazes, including a chart showing the Silica/Alumina ratios of several kinds of purple glazes, Britt offers four types of purple glazes: Magnesium Matte Purple, Glossy Purple, Nickel Purple, and Manganese Purple. Under the heading Magnesium Matte Purple, he presents seven different glazes, again laid out on a grid so that you can readily see the components of each glaze for comparison. The secret to producing one of these glazes is immediately obvious: the presence of Cobalt Oxide or Carbonate and Tin Oxide.

Britt’s single glaze for Nickel Purple is sub-titled “Poison Purple” (p. 117); one should be very cautious to avoid breathing the fumes from nickel during the firing. He notes that “nickel if fickle” and very difficult to work with since it can cause glazes to run. I will not be using Nickel Purple.

If you are a fan of ash glazes, Britt’s efforts here are notable: the sub chapter on such glazes (pp. 161-167) presents a variety or types of ash glazes. I counted 14 recipes for ash glazes, 6 for “fake ash,” and 9 for “slip-based ash.” The last two types “contain significant amounts of slip clays like Alberta slip or Redart as well as kaolins and ball clays; some of them do contain at least a small amount of real wood ash. Britt notes, “Fake-ash glazes are indistinguishable from wood-ash glazes, and are sometimes preferred because whiting is more stable than wood ash. Fake-ash glazes are very reliable, don’t require the collection or preparation of ash, nor do they exhibit the problem associated with soluble alkali. Whiting and ash can often be substituted for each other without a noticeable difference in the quality of the glaze” (p. 164). I consider these last statements to be of singular importance to the studio potter.

Britt ends his book with analyses of glaze materials (spars, frits, etc.), cone/temperature equivalents, and a valuable glossary (e.g., “Colloid. Tiny particles that are suspended in another substance; halfway between a solution and a suspension. Can create colloidal opacity or milky opalescence” (p. 172). If you check the General Index, you will find that Colloidal opacity is discussed on p. 21. Finally: the Glaze Index by Type: Ash, Black, Blue, Copper, etc. In short, this text is very easy to use as a reference; you can track a particular glaze or other topic in a variety of ways.

Clearly, this is a logically and thoroughly constructed text. Britt’s writing is some of the clearest one will find in writings on ceramics. He has de-mystified much of glaze preparation and, most especially, firing. I very much appreciate John Britt’s attention to safety in handling and firing glaze chemicals. Out of a possible five, I give this book five stars.
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