Glaze Fire Ceramics In The Campfire!
Is it possible to melt a pottery glaze at temperatures as low as 450 – 600°C?
That’s campfire temperatures, just perfect for grilling sausages, but if you fire clay at 450 – 500°C – it’s still just clay when it’s cooled down! Clay needs 600°C or higher just to sinter.
But ChatGPT says yes you can melt a glaze at 450 – 600°C, so lets give it a try!
I decided to test both if ChatGPT has any idea what it is really talking about, and secondly; check if it is possible at all.
I think you can make some kind of glaze in these temperatures, and that’s what I’m trying to find out here on this page. I don’t talk about smoke-fire, fume-fire, or other techniques that just color the outer layer of the clay surface, here I try to develop “real” ceramic glazes that melt out and cover the pottery with a glaze layer.
I don’t measure the temperature, it gets as hot as it gets, I fire with 2-3 birch logs and put the pottery in between. And fires it in a semi-enclosed space, so the wind doesn’t lower the temperature (more about that later).
Glaze Fire Ceramics In The Campfire 600 °C
First I have to say my target is sculptural and visual glazes, you can’t expect anything near food-safe in these low temperatures. When that’s said; the first test was not bad at all! I have a stronger low-temp melting agent coming in the post in about a week, I do belive this can work!
Early testing – this webpage develops as I go:
Low-temperature pottery glaze 600 °C – Not much of a glaze, but I kind of liked it as a thin wash
1 part Litium Karbonate
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 enough, 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 Litium Karbonate
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 Litium Karbonate
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 Litium Karbonate
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 and is too dry, but Zink should have contributed to the melt.
2 part Litium Karbonate
1 part Gersley Borate
1 part Zink Oxide
1 part Quarts
1 part Kaolin
1/2 part Color stains
XX6 – Untested – Pearl Ash Blue Satin Glaze (from ChatGPT 500 °C)
30 part Pearl Ash
30 part Ferro Frit 3134
10 part Zinc Oxide
20 part Quartz
10 part Kaolin
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
Low-temperature melting flux:
840 °C – Gerstley Borate (where it begins to melt)
743 °C – Borax (Sodium Borate)
851 °C – Sodium Carbonate
851 °C – Sodium Bicarbonate (NaHCO₃) “Baking Soda” Decomposition to Sodium Carbonate at 100-250°C
825 °C – Calcium Carbonate
723 °C – Lithium Carbonate
420 °C – Zink Oxid (secondary flux)
891°C – Potassium Carbonate (K₂CO₃) “Salt of Tartar” – react with silica (SiO₂) at ~1000°C
Baking Soda … pure Baking Soda is only Sodium Bicarbonate (NaHCO₃). some commercial baking powders (not pure baking soda) may contain Sodium Diphosphate (Na₂H₂P₂O₇)
Glaze Fire Ceramics In The Campfire
| 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. Lead Compounds (e.g., Lead Oxide, PbO): Properties: Historically one of the most effective low-temperature fluxes. Melting Range: Can melt silica at temperatures as low as 600–800°C. Use: Used in traditional low-fire glazes and crystal glasses. Considerations: Toxic and largely avoided in modern ceramics due to health risks. 4. 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. 5. 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. 6. 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. In summary, the most effective low-temperature fluxes for melting quartz under 800°C are boron-based compounds (borax, boric acid), alkali fluxes (soda ash, potassium carbonate), and lead or lithium compounds. However, due to solubility, toxicity, or cost concerns, these are often used in fritted forms or combined with other materials. |
Check out my other glaze-test’s 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 Ceramics In The Campfire – January 2025