The vast majority of my pottery is fired to 1200C in an electric kiln. My first kiln was rated to go to 1280, but at the time we were living in a village where the mains voltage barely reached the UK standard. (230 V ±10%) and high stoneware firing was taking forever and wearing the elements far too fast. I quickly changed to Mid-range firing.
In the UK most potters and courses focus either on earthenware or stoneware. Earthenware gives a vast choice of colour and painterly decorative styles but remains porous and relies on the glaze to be watertight. Stoneware gives more robust non-porous ware. Colours at stoneware tend to be much more muted and earth-toned, but can also be much more exciting as they melt and react in the kiln to produce interesting effects.
The middle ground has not been nearly so well investigated. The product is still virtually non-porous but firing uses much less energy. Much more work in this area has been done in the United States. I had worked with Emmanuel Cooper’s wonderful glaze recipe book, which does have a mid-fire section, gathering a few extras from here and there and developing some of my own. I had shied away from American books on the subject in the past because almost every recipe I came across called for Gerstley Borate. This natural mined mineral is rich in boron, which is one of the few active fluxes at mid-range temperatures. However it has a number of problems. It is no longer mined in the USA and is not available in the UK. When I saw the announcement of John Britt’s new book I was encouraged to find that the sample I could view seemed not to rely entirely on Gerstley Borate. It was on pre-order at Amazon, but UK publication was supposed to be in time for Christmas. In fact they got supplies earlier than expected and it turned up in November. It was my second self-service Christmas present.
I’ve not had a chance to test out the recipes as yet but my impressions of the book are good. It is not a book on glaze theory and how to develop and test your own. Equally it is not simply a book of glaze recipes which gives you the list of materials for each and a few notes. It manages to hold that middle ground of educating about glaze, whilst providing hundreds of tried and tested useful recipes.
The glazes are grouped together by type, which might be an effect, a finish or a colour. There is a wide range. Within each group John then gives a table of a number of glazes laid out together for comparison and talks about the nature of these glazes, some of the physics and chemistry about why they work and advice on how one might go about adapting them.
Scattered liberally through the pages are photographs of finished pieces featuring the glazes, each labelled with a credit to the maker, the glazes used, where to find them in the book and the firing cycle used. Where a comparison of similar glazes is useful they are also shown on test tiles. I want to emphasise that I really do think this is a great book before a lay out my few criticisms.
The inclusion of so many wonderful photographs has meant that they often appear in the layout a few pages or sometimes more from the glazes they feature. They are well referenced back to the glaze so it is only slightly annoying to be flicking back and forth. However there is no reference from the glazes to the photos of work featuring them, which would have been a very handy addition.
There is a section on materials safety and the safety of the resulting glazes when in use. It was therefore a disappointment to find that in summary the section on safety basically says: be aware, read the data sheets. It feels like a bit of a cop-out. Especially when one of the photos features a lemon squeezer with a copper green crystalline glaze. Highly acid foodstuff in contact with a glaze which by definition is not well balanced because it has crystals, and has constituents which are listed by John as toxic.
Sadly the dreaded Gerstley Borate does feature quite heavily. John mentions that it is no longer mined and that people are working off old stock, or using substitutes. However he shies away from the quagmire of that particular debate.
I loved John’s wit on the subject of Floating Blue glazes. This is a chun-like glaze-in-glaze where light refractions and variations in opacity produce some beautiful effects. It is also notoriously fickle. As he says “… but if you choose this path, remember, Grasshopper, that someday you, too, will be visited by the dreaded pond-scum-colored load of pots.” Grasshopper is a reference to the iconic 1970s Kung Fu TV series featuring the late David Carradine which might be wasted on an audience of younger potters. The About the Author section at the end says that John and I graduated with our first degrees in the same year so I guess that’s why I found it quite so funny.
So, overall, and so far, highly recommended. Perhaps some more feedback after some testing in the new year. Which is a good cue to wish everyone a happy and prosperous 2015.
Mike's Pad 