Cone 6 Crystalline Glazes Bill Schran wschran@cox.net wschran@nvcc.edu This is my presentation at Lattice Structures, an international symposium and exhibition of crystalline glazes held in Kansas City, MO, September, 2005. Resources - 1975 The two main resources I had during my early research. Glazes for Special Effects by Hebert Sanders is out of print. David Snair’s article on crystalline glazes, “Ceramics Monthly”, December 1975. Starting Out • Crystalline glazes can be produced at cone six with minimal, affordable equipment and materials in a small home or school studio. • Safety should be #1 priority. • Success requires careful organized record keeping. Studio for One Artisan My studio in a one car garage. Close quarters, but workable for an individual. Shot of wheel and kiln. Studio for One Artisan - View 2 Another view showing wedging board and work table. Vented Kiln My set up for the kiln vent system. The vent motor is mounted on a board that I can set in the window opening while in use, and remove to secure window when not being used. Eye & Lung Protection It’s very important to wear proper lung and eye protection while working with many ceramics processes. A respirator that is fitted correctly and has the proper cartridge is necessary when weighing out/mixing dry glaze chemicals. A cartridge with a P100 rating is what should be used. For all grinding operations, impact resistant eye protection is mandatory. Mixing Glazes I mix 200 gram batches of crystalline glazes for testing. This is sufficient to glaze a larger pot or a couple smaller works. Each container has the recipe written on it. I prefer plastic for easy clean up, storage and the containers are non-breakable. Records of Glazes & Firings It’s important to keep accurate records. All glaze recipes are written allowing space to record results after the firing right next to them. All firings are recorded, carefully noting times and temperatures. Variables • Glaze/Application • Firing Beside the composition, glaze application and firing are the two most critical factors in the development of crystals. Generally, crystalline glazes are applied on the thick side. I mix my dry glaze ingredients with a CMC gum solution and brush up to 4 coats of glaze. As the crystalline glaze usually has little or no clay, the CMC will help keep the glaze in suspension and prevent thick applications of glaze from cracking while drying. Firing speed, temperature, crystal growing temperature and how long that temperature is held are factors in number and size of the crystals. ^6 MFE/Dan Turnidge Ferro Frit 3110 - 50% (GF 134) Zinc - 22.5% Silica (325M) - 22.5% Lithium Carbonate - 2 – 5% Titanium Dioxide - 1% A simple yet reliable crystalline glaze. MFE/Turnidge Example of MFE/Turnidge glaze using nickel oxide & manganese dioxide MFE/Turnidge Example of MFE/Turnidge glaze using cobalt & manganese dioxide ^6 HELEN’S/ ALTERED SNAIR Frit 3110 - 48.40% Zinc - 24.35% Silica - 17.95% Calcined Kaolin - 1.52% Titanium Dioxide - 7.78%(ALTER) Lithium Carbonate - 5% This was originally a cone 9 glaze from David Snair. We’ve altered the quantity of titanium and added lithium carbonate. Helen’s/Altered Snair Example of Helen’s/Altered Snair using cobalt, manganese & iron ^6 Untitled Frit 3110 - 28% Frit GF 106 - 25% Silica - 13% Zinc - 24% Titanium Dioxide - 2% Lithium Carbonate - 2% A very successful cone 6 glaze, but GF 106 is no longer available. Fusion Frit #413 has been used as a substitute. Untitled Glaze Example of Untitled glaze using cobalt & manganese Untitled Glaze Example of Untitled glaze using cobalt & manganese , with an additional 2% titanium Untitled #2 Frit 3110 - 54 Zinc Ox. - 24 Silica - 23 Lithium Carb. - 3 Untitled #2 is similar to MFE/Turnidge, but even with minor changes, the results can be different. Untitled #2 Example of #2 using nickel oxide Manual Firing Schedule Manual Kiln, L&L, J18X, 3 sections, infinite switch for each section. • Kiln on high • ^6 over in 4 1/2 hours • Kiln off, drop to 1000 – 1040°C (1835 – 1905°F) about 30 – 45 minutes • Kiln on, switches vary between “L” – “2” • Hold temperature 4 hours This is my firing schedule using an L&L, J18X kiln with three sections, each section controlled by a manual adjusted infinite control switch. Programmed Firing Schedule L&L J18X-3, Dynatrol Controller • USEr/1 • SEG/2 • rA1/500 • °F1/2230 • HLd1/.05 • rA2/500 • °F2/1800 • HLd2/4.00 This is the program entered into a Bartlett controller on a L&L, JD18X-3 kiln. Pots/Pedestals/Catchers Example of pot (left) with brushed on glaze, pedestal (mix by volume: 1/3 alumina, 1/3 kaolin, 1/3 sawdust) and glaze catcher plate. Example of pot after firing: pot breaks away from pedestal to be ground smooth. Catcher holding excess glaze. Grinding A bench grinder with silicon carbide grinding wheel to coarsely remove glaze and pedestal pieces. Note that I’m wearing respirator and eye protection, and doing the grinding outside of the studio. Finishing Final grinding and smoothing is done with a flat lap machine using diamond disks. Since this process uses water, no dusts are created. Unsuccessful Tests Even after hundreds of tests, one can still get some unsuccessful results. Oops! Even after years of working, accidents still happen, this time too much glaze running into the catcher. Same Colorants Different Results The same colorants, nickel, manganese and iron, but in different proportions, can end in very different results.