Extreme Low-Fire glazes – Glaze Fire Ceramic In The Campfire!
Is it possible to melt a pottery glaze at temperatures as low as 550 – 600°C?
That’s campfire temperatures!
If you fire clay at 500 – 550°C, it will still be clay when it’s cooled down.
Can a ceramic glaze melt so low?
The answer is actually Yes, it’s possible!
(Not tested it in an electric kiln)
Here, I’m experimenting with extremely low, low-fire glazes, I don’t mean smoke-fire or other techniques that just color the outer layer of the clay surface; here, I try to develop “real” ceramic (campfire) glazes that melt out and cover the pottery with a glaze layer.
For high-fire pottery, there exist many different melting agents; for extremely low-fire glazes, on the other hand, there are just a few. Not many melting agents start to flux at these low temperatures. Several of them are also water-soluble, and some are even water-soluble after they are fired into a ceramic glaze. So here I target sculptural and visually appealing glazes; food-safe? In these low temperatures, I don’t know.
Extreme low-fire glazes require an exceptionally high percentage of flux, so the cost of achieving a melt at such low temperatures is glaze formulations are dominated by one or several melting agents, which means little room for other ingredients. The small space for non-flux ingredients can turn out to be a visual limitation for extremely low-fire glazes, we’ll see. As a rule of thumb, 3-4 parts flux to 1 part non-flux ingredients seems realistic.
Eutectic Melting & Glaze Experiments:
/how-low-can-you-go-pottery-flux
Glaze Fire Ceramic In The Campfire:
Extreme low-fire example glaze:
9 parts flux
2 parts Quarts
1 part “whatever you want.”
Examples of extremely low-fire flux glazes:
Glaze Fire Ceramic In The Campfire:
I don’t measure the temperature for these glazes; they are campfire-glazes, and it gets as hot as it gets, that’s what I develop them for. I fire with 2-3 birch logs and put the pottery in between. And I fire it in a semi-enclosed space, to make sure cold wind doesn’t lower the temperature (picture is coming). Even though my “kiln” is not hotter than 600 °C, the flames are hotter, “dancing flames” can maybe for a short time on local spots, contribute to a much higher temperature and melt. This seems to make strong variations in many of the glazes.
I do not use Lead due to health and environmental concerns. Lead is a strong low-temp flux.
Read about the 9 essential fluxing agents here:
important-fluxing-agents-in-the-pottery-studio/
Also, read about how to bisque fire ceramic in an ordinary wood stove:
fire-ceramic-in-a-wood-stove/
Glaze Fire Ceramic In The Campfire at 600 °C. Extreme low-fire ceramic glazes:
These tests are not for making cool glazes; they’re for finding strong melts and good material combinations. Though some are cool as-is.
Lithium dry yellow wash
XX00 – 600 °C Not much of a glaze, but I kind of liked it as a thin wash
1 part Lithium Carbonate
2 part Gersley Borate
1 part Sodium Bicarbonate (Soda Ash/Baking Soda)
1 part Sinkoxid
1 part Quarts
1 part Kaolin
1 part Iron oxid
Borax frit semi-melted glaze
XX01 – 600 °C – It starts to melt when thick, but the frit is not active enough in these low temperatures.
2 part Borax Frit P2953.1
1 part Color stains
Lithium melted glaze
XX02 – 600 °C – Now this is more like it: 4 of 5 parts in this glaze are a flux, and it starts to melt, the glaze should have been thicker.
2 part Lithium Carbonate
2 part Gerstley Borate
1 part Quarts
1 part Kaolin
1/2 part Color stains
White-blue dry glaze
XX03 – 600 °C – No, Strontium did not add to the melt.
1 part Gersley Borate
1 part Lithium Carbonate
1 part Strontium Carbonate
1 part Quarts
1 part Kaolin
1/2 part Color stains
To dry wood ash glaze
XX04 – 600 °C – Did not melt; after a minute in water, it could be peeled off.
1 part Lithium Carbonate
1 part Gersley Borate
2 part Birch Wood Ash
1 part Eggshell (Calcium Carbonate alternative)
1/2 part Color stains
Lithium dry glaze
XX05 – 600 °C – Dry, Zink did not contribute to the melt, to little Quarts.
2 part Lithium Carbonate
1 part Gersley Borate
1 part Zink Oxide
1 part Quarts
1 part Kaolin
1/2 part Color stains
First “real” extreme low-temp glaze
XX06 – 600 °C – Melts well; this is a real low-temperature glaze! Strong color variations from green, rust, yellow, and brown. Inside, and out of reach from the flames, the glaze has not melted and can be piled off.
3 part Borax
2 part Gersley Borate
1 part Lithium Carbonate
1 part Sodium Carbonate (baking soda)
2 part Quartz
1 part Kaolin
1/4 part Copper carbonate
Lithium Borax glaze
XX07– 600 °C – When the heat starts to build up, this glaze begins to make bubbles. That’s not a good sign, but it seems to melt and layer back again to the surface. When thick enough, it gets glossy, where the piece has been in reduction, it’s metallic gray; in oxidation, red, brown, and dark. This is definitely forming a glaze. When glaze fire ceramic in the campfire, the objects will eventually fall down, and ember, coal, and ash will stick to the melt.
1 part Lithium Carbonate
1 part Borax
2 part Quarts
1 part Kaolin
1/4 part Copper carbonate
Four flux – red-brown-blue glaze
XX08 – 600 °C – When the glaze is thicker, it develops a nice blue color. The white balls are Borax; heat seems to make “crystall-balls”, if the temperature gets higher, they melt into the glaze. Only objects in the hottest zone melted. It is possible to make a melt without Lithium at these temperatures, but it’s harder; both Gersley Borate and Colemanite raise the melting point too.
2 part Borax
2 part Gersley Borate
2 part Sodium Carbonate (baking soda)
1 part Colemanite
2 part Quarts
1 part Kaolin
1/4 part Copper carbonate
Chocolate black glaze
XX09 – 600 °C. A full-scale, extreme low-fire glaze, dark, greate, needs to have some thickness, green-blue as thin, dark brown as thick.
3 part Sodium Bicarbonate (Soda Ash/Baking Soda)
2 part Borax
1 part Lithium Carbonate
1 part Feldspar Soda
2 part Quarts
1/2 part Bentonite
1/2 part Iron Oxide Yellow
Sodium chocolate brown glaze
XX10 – 600 °C – Except for one dry area without glaze (I don’t know what happened there). The chocolate brown glaze, not too appealing when thick, has potential.
3 part Sodium bicarbonate (Soda Ash/Baking Soda)
2 part Borax
1 part Rutil
4 part Quarts
1/2 part Bentonite
1/2 part Iron Oxide Yellow
1/2 part Copper carbonate
Borax and Talc – brown, blue/green glaze
XX11 – 600 °C – Very distinct color differences; maybe the glaze-thickness makes the difference? The brown picks up some classic wood-fire colorations at a really low temperature. I expected the talcum to add a brighter expression.
4 part Borax
1/2 part Lithium Carbonate
1 part Talc
1/2 part Bentonite
4 part Quarts
1/2 part Copper carbonate
Pure Borax glaze
XX12 – 600 °C – This has nothing to melt except Borax, it is hardly a glaze and feels like painting with sand. Borax has a high Boron content, and Boron is a strong glass-former.
100% Borax
Beautiful Blue – Largely unmelted glaze
XX13 – 600 °C – Melted out in the hottest flames, but most unmelted. Looks like a great glaze with beautiful blue/yellow/brown colors, but it really needs some 50-100 degrees C extra or more flux. Sadly, adding small amounts of Talc, Magnesium, and Kaolin is enough to reduce the flux domination over its melting point.
3 part Borax
2 part Gerstley Borate
1 part Lithium Carbonate
1 part Talc
1 part Magnesium Carbonate
4 part Quarts
1 part Kaolin
1/2 part Copper carbonate
Unmelted dry glaze
XX14 – 600 °C – Not enough fluxing agents, too large amounts of other substances, too little flux. It has melted some “pearls” spotted around, maybe it’s Borax pearls?
2 part Borax
1 part Lithium Carbonate
2 part Talc
1 part Magnesium Carbonate
1 part Kaolin
3 part Quarts
1/2 part Yellow iron oxide
Strontium semi-matte hard glaze
XX15 – 600 °C – Glossy hard surface, complete melt, nice feeling. This is a good low-fire glaze.
4 part Borax
2 part Gersley Borate
1 part Lithium Carbonate
1 part Strontium
2 part Quarts
1/2 part Yellow iron oxide
Sodium Borax Rutil glaze
XX16 – 600 °C – Melts well, chocolate as thick, light brown as thin, both thin and thick layers work well.
3 part Borax
3 part Sodium bicarbonate (Soda Ash/Baking Soda)
1 part Lithium Carbonate
1 part Rutil
1 part Kaolin
3 part Quarts
1/2 part Yellow iron oxide
Tin oxide white glaze
XX17– 600 °C – It is not successful as a white covering glaze, but it does melt! Maybe Borax makes this uneven. To the right is the same glaze, but it ended up a little out of the hot flame-zone; it is so dry it can be washed off.
4 part Sodium bicarbonate (Soda Ash/Baking Soda)
2 part Borax
1 part Tin oxide
1 part Kaolin
5 part Quarts
Sand color glossy glaze
XX18 – 600 °C – Melted partly in the hottest flames, with too little fluxing agents. Interesting to see that it can melt without Lithium.
3 part Borax
2 part Sodium Carbonate (baking soda)
1 part Talc
1 part Feldspar
5 part Quarts
1 part Kaolin
1/2 part Yellow iron oxide
Vine-red/brown – largely unmelted glaze
XX19 – 600 °C – It is Largely unmelted, but triple the flux amount could get interesting results.
2 part Borax
1 part Sodium Carbonate (baking soda)
1 part Aluminium oxide
5 part Quarts
1 part Kaolin
1/4 part Copper carbonate
Untested – Potassium glaze
XX20 – 600 °C – not started to test with Potassium.
3 part Potassium
2 part Sodium Carbonate (baking soda)
2 part Borax
3 part Quarts
1 part Kaolin
1/4 part Copper carbonate
Dry Lithium Base glaze
X21 – 600 °C – Interesting. I can’t answer why it has green color spots.
My version of Jennifer Harnetty's cone 010 900 °C glaze (300 °C lower):
2 part Lithium Carbonate
1 part Kaolin
4 part Quarts
1/2 part Bentonite
1/4 part Copper carbonate
I found this low-temperature glaze by Jennifer Harnetty
27.5% - Lithium Carbonate
15.5% - Tile 6 Kaolin
54.0 - Silica/Flint/Quarts
3.0% - Bentonite
100% Tot
Boric Acid glaze – too dry
XX22 – 600 °C – Too dry, not melted, did it flux Quarts at all? By scrubbing my finger on the surface, small crumbs are falling off; I can even peel off flakes in some places. Not what I hoped for, but the coloration is interesting.
3 part Boric Acid
3 part Quarts
1 part Kaolin
1/4 part Copper carbonate
The start of a volcanic glaze? Boric Acid
XX23 – 600 °C – The start of a volcanic glaze? Good melt! The coloration is a bit boring, and the surface has small pinholes. Maybe it needs to hold the maximum temperature a bit longer?
 | |
3 part Boric Acid
2 part Sodium Carbonate (American baking soda)
3 part Quarts
1 part Kaolin
1/4 part Copper carbonate
Boric Acid glaze – unmelted
XX24 – 600 °C – Unmelted, too dry, by scrubbing my finger on the surface, small crumbs are falling off, too much Quarts?
3 part Boric Acid
2 part Borax
1 part Lithium Carbonate
5 part Quarts
1 part Kaolin
1/4 part Copper carbonate
Boric Acid melted glaze with surface variations
XX25 – 600 °C – I like this glaze; in the hottest parts, the glaze melted to a nice glossy surface without cracks. On the other side of the ceramics, the glaze is semi-glossy, but it’s a melted and hard surface.
2 part Boric Acid
2 part Borax
2 part Gersley Borate
2 part Sodium Carbonate (baking soda)
5 part Quarts
1 part Kaolin
1/4 part Copper carbonate
Untested – Boric Acid glaze
XX26 – 600 °C – hhh
8 part Boric Acid
2 part Quarts
1 part Kaolin
1/2 part Yellow iron oxide
Untested – Boric Acid glaze
XX27 – 600 °C – hhh
8 part Boric Acid
2 part Sodium Carbonate (baking soda)
1 part Strontium Carbonate
2 part Quarts
1 part Kaolin
1/2 part Yellow iron oxide
End of testing (for now).
Glaze Fire Ceramic In The Campfire
Check out my other glaze-tests here:
Check out how to fire ceramics in a wood stove:
Check here how to make strong pottery vessels in primitive firing:
make-strong-pottery-for-primitive-firing/
Glaze Fire Ceramic In The Campfire – January 2025
Also two links with ideas:
https://ceramicartsnetwork.org/daily/article/Five-Low-Fire-Alkaline-Glaze-Recipes
https://ceramicartsnetwork.org/daily/article/3-Awesome-Low-Fire-Glazes-Perfect-for-Clay-Sculpture
Glaze Fire Ceramic In The Campfire