Once Firing – Greenware Glazing
Testing New Ceramic Glazes: Cone 06 – 1000°C – 1830°F.
Burned in this kiln: /the-mediterranean-kiln-made-simple/
These glazes are fired like this: Wood-fired up to 1000 degrees Celsius in 3 to 4 hours, in an updraft ceramic kiln. Hold for 30 minutes, and down again in 3-4 hours.
I have worked with white glazes here: /white-low-fire-glazes-for-terracotta/
This is a work-in-progress webpage. I will test more glazes throughout the summer of 2026.
(Work in progress low-fire greenware Glazes)
All glazes are measured by weight:
GG_1000C_001
20 – Gersley Borat
20 – Colemanite
10 – Feldspar soda
10 – Light Rutile
10 – Kaolin
5 – Bentonite
20 – Quarts
—
5 – Copper Carbonate
5 – Red iron oxid
Forgot the color oxids
Fired all too high, the glaze should be glossy, but when fired too high, it dripped off onto the pottery lower down, and then the flux boils, froths, or volatilizes boron oxides, leaving the glaze all too dry; try again.
GG_1000C_002
Green glossy
20 – Gersley Borat
10 – Colemanite
20 – Sodium bicarbonate
10 – ball clay
10 – Bentonite
30 – Quarts
—
5 Copper Carbonate
Difficult to apply evenly with a brush, even the slightest touch makes the dry glaze crumble off.
The glaze was burned too high; try again.
GG_1000C_003
Fired in a reduction atmosphere
30 Sodium bicarbonate (household product)
30 Gerstley Borate
20 Nepheline Syenite
10 Rutil
20 Ball clay
20 Quarts
20 Iron oxide black
Testet på vase – The darkest hour
GG_1000C_004
50 Borax Frits P2953.1
30 Zinc oxide
30 Talc
10 Quarts
10 Kaolin
5 Rutile
5 Copper carbonate (original with 5 Iron oxide black)
Var 2: Trouble converting to once firing.
Var 1: Dry, yellow gray, Interesting; dark gray as thick, yellow as thin, can I change the colors? Inspired by: 30-Borax-E-Frit-P2953-1_30-Zink_30-Talc_10-Kaolin.html
GG_1000C_005
30 – Gerstley Borate
20 – Sodium bicarbonate
20 – Wood Ash
10 – Kaolin
20 – Quarts
—
5 – parts Iron Oxide Red
Nice and smooth to apply with water and a brush. Bad picture, but this is a good glaze! I did not apply it too thick, and the green color was dripping from the other glazes.
GG_1000C_006
20 – Gerstley borate
20 – Sodium bicarbonat
10 – Light Rutile
10 – Tin oxide
10 – Kaolin
30 – Quarts
—
5 – Red stains
Dry, interesting, but needs to be more glossy
GG_1000C_007
20 – Borax
20 – Gerstley borate
20 – Sodium bicarbonat
20 – Kaolin
20 – Quarts
As a base glaze, it has some problems with pinholes and cracking, but it’s a good start, and I like the hard surface. Over-fired with maybe 150 degrees.
GG_1000C_008
40 Gerstley Borate
20 Nepheline Syenite
10 Kaolin
10 Ball Clay
10 Chalk (CaCO₃)
10 Zinc Oxide
Colorants:
10 Magnesium carbonate (should have been 10 Manganese Dioxide)
10 Red Iron Oxide
Charcoal black, semi-gloss, too runny, I like it, but need some adjustments.
GG_1000C_009
10 Gerstley Borate
10 Quarts
10 Ball clay
10 Rutile
10 Strontium carbonat
30 Yellow Iron Oxide
Thin Wash needs a lot of water to make the glaze thin. I like it as-is!
GG_1000C_010
20 Gerstley borate
20 Sodium bicarbonate (household product)
50 Quarts
10 Kaolin
5 Copper Carbonate
Best as thick, glossy but not runny, I like it, tension makes the glaze withdraw from angles.
GG_1000C_011
20 Borax
30 Sodium Carbonate (Soda Ash)
30 Quartz
30 Kaolin
5 Copper carbonate
High surface tension can come from too much clay. Here I tried variant D but didn’t solve it. The glaze was extremely runny, and most of the glaze melted and dripped off.
GG_1000C_012
20 Borax
10 Lithium Carbonate
30 Sodium Carbonate (Soda Ash/Baking Soda)
30 Quartz
40 Kaolin
10 Copper carbonate
(mix borax well with the other powders before adding water)
(fired in reduction atmosfere)
Blue and black, glossy, interesting, strange. The day after the firing, white spots showing up can be washed off, metal-salt sweating? Surface tension: Sharp edges have too little glaze.
GG_1000C_013
60 – Ferro Frit 3134
10 – Chalk
10 – Kaolin
30 – Quarts
GG_1000C_014
30 – Alkali Frit P2962.1
20 – Feldspar Soda
20 – Magnesium Carbonate
10 – Chalk
10 – Kaolin
10 – Quarts
GG_1000C_015
50 Colemanite
30 Feldspar Soda
10 – Kaolin
10 – Quarts
—
10 – Burnt Ocer
GG_1000C_016
100 parts – P3124.1 Borosilikat Ferro fritte
50 pars – Yellow Iron Oxide
10 parts – Ilmenite
20 parts – Kaolin
20 parts – Quarts
Ox950C_06C new try.
10 Borax
30 Sodium Carbonate (Soda Ash)
30 Quartz
20 Ball clay
5 Copper carbonate
Ox950C_07
Green, black glossy, need to be thick
70 Gersley Borate
30 Feldspar Soda
20 Kaolin
10 Iron Oxide Red
Ox950C_09b
2 part Sodium Carbonate (Soda Ash/Baking Soda)
1 part Borax
2 part Feldspar Soda
1 part Quarts
2 part Kaolin
1/2 part Iron Oxide Yellow
Ox950C_11(inspired of XX11 – 600 °C)
Not yet tested
2 part Borax
1 part Colemanite
1 part Talc
4 part Bentonite
2 part Quarts
1/2 part Copper carbonate
Ox950C_13 (inspired of XX13 – 600 °C) (fired in reduction atmosfere)
A strange glaze, uneven, I like the matte and white part. Surface tension: Sharp edges have too little glaze.
2 part Borax
2 part Colemanite
1 part Lithium Carbonate
1 part Talc
1 part Magnesium Carbonate
3 part Quarts
4 part Kaolin
1/2 part Copper carbonate
Ox950C_13b
2 part Borax
2 part Colemanite
1 part Talc
1 part Magnesium Carbonate
3 part Quarts
2 part Ballclay
1/2 part Copper carbonate
Ox950C_15(inspired of XX15 – 600 °C)
Y
1 part Borax
2 part Colemanite
1 part Sodium Carbonate (Soda Ash/Baking Soda)
1 part Strontium
2 part Quarts
1 part Kaolin
2 part Ballclay
1/2 part Yellow iron oxide
Ox950C_17 (XY)
Cracked intense green
60 Borax Frit P2953.1
10 Ballclay
50 Quarts
5 Rutile
10 Iron Oxide Yellow
Try using strontium
Once Firing – Greenware Glazing, Testing New Ceramic Glazes
Testing New Ceramic Glazes, 2026