Cone 6 Crystalline Glazes Bill Schran

Cone 6 Crystalline Glazes
Bill Schran
[email protected]
[email protected]
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.
• 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.
Example of MFE/Turnidge glaze
using nickel oxide & manganese
Example of MFE/Turnidge glaze
using cobalt & manganese dioxide
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.
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.
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.
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.
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.