of crystalline glazes is one of the more difficult challenges a potter
can face. Since the 1850s the process has fascinated - and in some
cases obsessed - a small number of potters in various countries. Peter
Ilsley, who has been potting professionally since 1963 and has had
periods of "playing with" crystals at roughly five-year intervals. In
January 1989 he made a total commitment to the problem of consistently
producing quality crystals. Hundreds of firings were done and
hundreds of pots scrapped before he was able to achieve his goal.
He wrote his book, ‘ Macro Crystalline Glazes’ which was published by ‘Crowood Press' as an A4 hardback at £25 in June 1999, it features some of the leading ceramists/potters working in this field at the time.
Ilsley's porcelain pots are sprayed and/or dipped with zinc silicate containing zinc and silica which are often but not always, "seeded" with titanium dioxide at 1300°centigrade to form the nuclei of the spectacular flowers which then develop organically in the glassy magma during a soak between 1100°c and a 1000°c on the cooling cycle lasting up to five hours.
peak temperature is critical - a few degrees too much will cause most
of the glaze to run off the pot, consequently the pots have to be fired
on their own pedestals, with a small bowl to catch the glaze run-off.
Otherwise they would be welded to the kiln shelf. Too low a temperature
produces something akin to galvanised iron! The clay, the glaze
composition, its application and the firing cycle all play a vital and
complex part in the transformation.
"The variables are phenomenal — and for me that is one of the great fascinations of the process," says Ilsley. "The number of crystals forming in the glaze and their location on the pot cannot be precisely controlled. But with careful attention to every detail of the making process, which is enormously time-consuming, some repetition of fairly similar characteristics can be achieved. When I first managed to produce well-defined and reasonably-sized crystals I had a fantastic feeling of achievement. The delight is still with me. The challenge to produce new variations of form and colour is still there. My experiments will go on".
Work generally available from:
Whilton Locks Pottery, Whilton Locks, Nr.Daventry, Northants. 01327 842 886
Contemporary Ceramics, 7 Marshall Street, London. W1V 1LP. 020 7437 7605
The clay bodies I am currently using, are Limoges 1400 porcelain and
Valentines, Audrey Blackman porcelain, fired to cone 9 in an electric
kiln. Some of the pots are selected after their initial firing and
reduced in a gas fired kiln, to create copper crystals, reds and
The glazes I use are based on three frits — Ferro 3110 and Fusion 644 and a base glaze, which I prepare from raw materials. The crystal growth and the growth rings are created by much kiln manipulation. Each raising and lowering of the temperature creates another halo.
I came to ceramics in 1963. My work since then has embraced a wide
range of domestic stoneware and a series of one-off stoneware,
earthenware, porcelain and "Raku" pieces.
In January 1989 I made a total commitment to crystalline glazes, something I had attempted to produce at approximately five-yearly intervals since 1963, with very little success.
From 1989 I produced, in hindsight, some quite insignificant crystalline pieces, but these gave me the impetus to go on and become totally involved in research and experimentation. The commitment became an obsession, which remains with me, to the point whereby 95% of my time and production is given over to crystalline pieces.
I wrote the book on 'Macro Crystalline Glazes', which was published by ‘Crowood Press' as an A4 hardback at £25 in June 1999, it features some of the leading ceramists/potters working in this field.
In 2000 Peter bought a house in southern Spain, where he retreat's to at the beginning of November until early April each year, so that during the grey wet English winters he will be throwing and biscuit firing his porcelain pots in the warm Spanish sunshine, ready to transport back to England for their glost firings.