How To Make DIY Pottery Glazes For Wood Firing
Sure you can buy commercial glazes; they are professionally made, stable, repeatable, and easy to use. For many potters, reliability is more important than experiments.
Consistency is their greatest strength. The higher price and the fact that thousands of other people are using the exact same glaze may be their weakness.
Mixing homemade glazes for pottery from scratch is not difficult. Often, you use twice as many ingredients in your dinner recipe. Cheaper than commercial glazes, the potential for uniqueness, and your growing material understanding, can be DIY glazes greatest strengths. The weakness can be the required time; developing a stable glaze demands repeated firings and refinement. Luckily, there exist tens of thousands of raw-material glazes, which means you can start your journey based on other potters’ formulas and experiences.
DIY Pottery Glazes For Wood Firing
Glazes for wood firing are not fundamentally different from glazes designed for electric or gas kilns. But they can be formulated to interact with flame, ash, and heavy reduction.
We can use materials such as sodium compounds, borates, lithium carbonate, and copper oxide that volatilize, flash, or migrate in ways that can harm electric kilns.
Wood firing introduces active variables that do not exist in gas kilns.
Flames and smoke carry alkaline fluxes released from burning wood — primarily potassium (K₂O), sodium (Na₂O), and calcium (CaO). These materials travel through the kiln as vapor and ash, becoming part of the glaze during firing.
Ash in it self is a functional glaze ingredient. Direct flame contact alters the melt, color, and texture. Ash streaking and surface variation can not be reproduced in other kiln environments. Glazes for wood firing are often designed to respond to the kiln atmosphere. Volatile materials can be used more freely. Time becomes part of the glaze chemistry and visual appearance. Long firing cycles and soaking periods, repeated shifts between oxidation and reduction, evolve glazes over time. In wood firing, a glaze is not a closed recipe but an interaction with the kiln environment.
What makes a ceramic glaze?
You don’t need to be a material science expert, but it helps to know some basics. A bonus is that making raw-material glaze often costs 1/10 of the price of a commercial glaze.
You don’t need so many raw materials to make a glaze, and still they can be mixed in countless combinations, resulting in an endless myriad of different glaze recipes, something ceramists often generously share with others. Ceramics are glazed for aesthetic and decorative reasons, and to make ceramic wares water-tight and food-safe.
Not only the receipt, but also the firing temperature, the kiln atmosphere, the glaze thickness, and many other factors influence the final result.
See the page for ceramic glazes receipts here:
/new-low-fire-ceramic-glaze/
A ceramic glaze recipe contains different types of inorganic materials ground into powder, mixed with water to a creamy consistency, and applied with a brush, dipped, or sprayed on the surface of clay or bisque-fired ceramics. The components melt onto the ceramic surface and transform into a hard, durable coat on top.
Developing a food-safe and production-ready glaze can be a lot of work. If that’s your goal, start with a few of the classic materials and receipts; they are well-tested and loved for their appearance. You can carefully bend them with color Oxides til you find your palette.
More about glazes in Wikipedia: https://en.wikipedia.org/wiki/Ceramic_glaze
"Essentially, glaze is a layer of glass fused to the surface of pottery. It can provide a smooth, hygienic surface that is non-porous whilst at the same time being decorative"
From "Ash Glazes" by Phil Rogers.
The 3 components that make a glaze
- Flux is the melting agent(s)
- Glass formers like Quartz or Silica (SiO₂)
- Stabilizers, Alumina (Al₂O₃) is the primary stabilizer
- Colors are primarily produced by metal oxides
The 3 key components that make a glaze:
Flux – the melting agent
Flux is the reason why we can sinter clay and melt glazes in a regular kiln; fluxes fuse with other components and lower the melting temperature. Flux often melts poorly on its own, but reacts strongly with other materials. Causes glazes to melt, and clay to sinter at much lower temperatures. A higher amount of flux lowers the melting temperature. 40 – 80% flux is a common percentage in low-fired glazes.
How to make DIY pottery glazes for wood firing:
List of Fluxing agents for ceramics and ceramic glazes:
1 – Boron(B)
2 – Calcium(Ca)
3 – Feldspar (not a single flux but a family of fluxes)
4 – Lithium(Li)
5 – Magnesium(Mg)
.. – Manganese(Mn)
6 – Potassium(K)
7 – Strontium(Sr)
8 – Sodium(Na)
9 – Zink(Zn)
Read more about these fluxing agents here, and why I chose 9 primary raw-material fluxes for ceramics:
Also, check out the raw material list here:
/ceramic-materials-and-glaze-ingredients/
Glass-former
Glass formers provide structure and stability to the glaze. Silica – Silicon Dioxide SiO2 (usually in the form of flint or quartz) is the primary glass former in most glazes, and contributes to the glassy matrix. The ratio between the glass-former and the fluxes determines (together with the temperature) the viscosity of the glaze melt. A balance between fluxing agents and glass formers is a goal when designing a new glaze.
Stabilizer
Stabilizers help control the thermal expansion and contraction of the glaze during heating and cooling in the ceramic kiln. Stabilizers play a crucial role in ensuring that the glaze adheres to the ceramics. It reduces the risk of crazing (fine cracks in the glaze surface) due to different thermal expansion between the glaze and the ceramic body.
Kaolin (clay mineral rich in alumina and silica), Aluminium Oxide, and Bentonite are examples of stabilizers.
Colors
Almost all colors in ceramics are made with one or more metal oxides: Iron Oxide, Cobalt Oxide, Copper Carbonate, Chrome Oxide, and Manganese Dioxide are all examples of much-used colors. More often than not, mixing several Oxides is necessary to give the right color palette and visual effects.
Most ceramic colors and fluxes are made of different metal oxides; some colorants can have fluxing characteristics, and some fluxing agents can give coloring effects. Careful consideration of the different components is essential for achieving the desired result.
Commercial Frits and Stains (colorants) can contain more dangerous metal Oxides, but are bound in glass and pulverized, something that makes them less unhealthy to work with.
How to make DIY pottery glazes for wood firing:
You can also read more on these selected internet resources:
A-Super-Simple-Analogy-to-Help-You-Understand-Glaze-Structure
thelittlepotcompany.co.uk/blogs/pottery/making-your-own-pottery-glaze
oldforgecreations.co.uk/blog/first-five-ingredients-where-to-start-with-glaze-making
“How To Make DIY Pottery Glazes For Wood Firing”. Jan 2025