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! Perfect for grilling hot dogs.
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!
(but I have not tested it in an electric kiln, maybe direct flames are also needed)
Here I am searching for 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.
About extreme Low-Fire glazes:
For high-fire pottery there exist many different melting agents, for extreme low-fire glazes on the other hand, there are just a few. Not many melting agents start to flux in these low temperatures. Several of them are also water-soluble, and some are even water-soluble after they are fired in the ceramic kiln. So here I target sculptural and visually appealing glazes, I don’t know if food-safe is even possible in these low temperatures.
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 dominated by one or several melting agents, that again leaves little room for other ingredients. The small space for non-flux ingredients, can maybe be a limitation when designing these extreme low-fire glazes. But time will show.
The first low-fire glaze test was not bad at all! And there are still some 2-3 strong low-temp melting agents I’m about to buy.
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 locally and for a short time contribute to a much higher temperature, how much this contributes to the overall melt is hard to say.
Worth mentioning: I do not use Lead and Barium due to health and environmental concerns, both act as strong low-temp fluxes.
Also, read about the 9 essential fluxing agents here:
important-fluxing-agents-in-the-pottery-studio/
Glaze Fire Ceramic In The Campfire 600 °C
Low-temperature pottery glaze 600 °C
Yellow wash
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 (baking Soda)
1 part Sinkoxid
1 part Quarts
1 part Kaolin
1 part Ironoxid
Low-temperature pottery glaze 600 °C
White-blue semi-melted.
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
Low-temperature pottery glaze 600 °C
Blue semi-melted.
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 Gerstley Borate
2 part Lithium Carbonate
1 part Quarts
1 part Kaolin
1/2 part Color stains
Low-temperature pottery glaze 600 °C
White as thin, blue as thick. 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
Low-temperature pottery glaze 600 °C
White-blue. 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
Low-temperature pottery glaze 600 °C
White-blue has not melted, is too dry, Zink did not contribute to the melt.
2 part Lithium Carbonate
1 part Gersley Borate
1 part Zink Oxide
1 part Quarts
1 part Kaolin
1/2 part Color stains
Low-temperature pottery glaze 600 °C
Unpredictably and interesting.
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
XX6 – Low-temperature pottery glaze 600 °C
First “real” glaze.
Melts good, now this is a real low-temperature glaze. Strong color variations from green, rust, yellow, and brown. Interestingly; inside, out of reach from the flames, the glaze has not melted and can be piled off.
2 part Gersley Borate
1 part Lithium Carbonate
3 part Borax
1 part Sodium Carbonate
2 part Quartz
1 part Kaolin
1/4 part Copper carbonate
Mixed in Vodka mix, not water
XX7 – Untested – Dry Lithium Base Cone 010 (900 °C)
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
XX8 – Low-temperature pottery glaze 600 °C
Nice red-brown to blue glaze.
When the glaze is thicker it develops a nice blue color. The white spots are unmelted Borax, only objects in the hottest zone melted, it is possible to make a melt without Lithium in these temperatures, but it’s harder, both Gersley Borate and Colemanite raised the melting point too.
2 part Borax
2 part Gersley Borate
2 part Sodium Carbonate
1 part Colemanite
2 part Quarts
1 part Kaolin
1/4 part Copper carbonate
XX09 – Untested – Tracking down a clear melt
2 part Lithium Carbonate
2 part Borax
2 part Sodium Carbonate
1 part Potassium Carbonate
7 part Quarts
1 part Kaolin
1/4 part red Stains
Glaze Fire Ceramic In The Campfire
Low-temperature melting flux:
Start to flux:
~750°C - Borax (Sodium Borate)
~750°C - Boric Acid (Do not contain Sodium)
723°C - Lithium Carbonate
891°C - Potassium Carbonate
~800°C - Sodium Carbonate/Bicarbonate (Soda Ash/Baking Soda)
(pure Baking Soda is only Sodium Bicarbonate (NaHCO₃), while Baking Powder is not pure baking soda).
~700-900°C - Calcium Fluoride (Fluorspar) (CaF₂)
contributes to eutectic melting
~750-900°C - Cryolite (Na₃AlF₆) fluoride-based flux
It does melt! But does a campfire reach 723°C? I find it a bit hard to belive, directly in the flames maybe, but the flames dance around. Maybe some melting starts at a lower temperature than this list says, or direct flame can locally and for a short time heat the glaze enough to start melting. I don’t see any third alternative.
Glaze Fire Ceramic In The Campfire
From ChatGPT:
| Below is a summary of low-temperature ceramic fluxes that can help melt or soften quartz at temperatures under 800°C: 1. Borax (Sodium Borate, Na₂B₄O₇·10H₂O): Properties: A powerful low-temperature flux that forms borosilicate glass when combined with silica. Melting Range: Can melt silica at temperatures as low as 600–800°C. Use: Commonly used in low-fire glazes and frits. Considerations: Highly soluble in water, so it is often used in fritted form. 2. Boric Acid (H₃BO₃): Properties: Another boron-based flux that effectively lowers the melting point of silica. Melting Range: Works well in the 600–800°C range. Use: Used in low-fire glazes and enamels. Considerations: Can volatilize at higher temperatures, so it is best suited for low-fire applications. 3. Soda Ash (Sodium Carbonate, Na₂CO₃): Properties: A strong alkaline flux that lowers the melting point of silica. Melting Range: Effective in the 700–900°C range. Use: Used in low-fire glazes and glass formulations. Considerations: Highly soluble in water, so it is often fritted or combined with other materials. 4. Potassium Carbonate (Salt of Tartar, K₂CO₃): Properties: A potassium-based flux that lowers the melting point of silica. Melting Range: Works in the 700–900°C range. Use: Used in low-fire glazes and historical glassmaking. Considerations: Highly soluble and hygroscopic, so it is often fritted. 5. Lithium Carbonate (Li₂CO₃): Properties: A strong flux that can significantly lower the melting point of silica. Melting Range: Effective in the 600–800°C range. Use: Used in low-fire glazes and specialty glass formulations. Considerations: Expensive compared to other fluxes. 7. Fluoride Compounds (e.g., Calcium Fluoride, CaF₂): Properties: Fluorides act as powerful fluxes and can lower the melting point of silica. Melting Range: Effective in the 700–800°C range. Use: Used in some low-fire glazes and enamels. Considerations: Can release toxic fumes during firing, so proper ventilation is required. 8. Phosphorus Compounds (e.g., Bone Ash, Calcium Phosphate): Properties: Phosphorus can act as a flux in combination with silica. Melting Range: Effective in the 700–800°C range. Use: Used in some low-fire glazes and specialty glass formulations. Considerations: Can affect glaze texture and color. Combination of Fluxes: Often, a combination of fluxes is used to achieve the desired melting behavior and glaze properties. |
Check out my other glaze-test here:
Check out how to fire ceramics in a wood stove:
Check here how to make strong pottery vessels for 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