From Bucket to Formula
Commercial glazes come ready to use. Once you start mixing your own, you unlock an enormous range of surfaces, colours, and textures unavailable in any commercial range, but you need to understand how glaze recipes work first.
What a Glaze Recipe Looks Like
A glaze recipe is a list of raw materials expressed as percentages by weight. They always add up to 100, or close to it. Colourants and additives are listed separately, as additions on top of the base 100.
A simple example:
- Potash Feldspar: 40
- Silica (325 mesh): 25
- Whiting: 20
- Kaolin: 15
- Total: 100
- Red iron oxide: 4 (addition)
The Main Material Groups
Every glaze recipe contains materials from these categories:
- Fluxes: Materials that lower the melting point and help the glaze melt at the target cone. Examples: Whiting (calcium), feldspar (potassium or sodium), talc, dolomite.
- Glass formers: Silica (flint or quartz) is the primary glass former: it creates the glassy quality of the fired glaze.
- Stabilisers: Alumina (from kaolin or alumina hydrate) keeps the glaze from flowing too much and gives it body and durability.
- Colourants: Metal oxides (iron, cobalt, copper, manganese, titanium) added in small amounts (1-10%) to produce colour.
Dig Deeper
The raw materials in a glaze recipe are the same minerals found in the earth's crust, and understanding their roles connects directly to the science of vitrification: the process by which silica and flux materials melt together to form glass. Kaolinite, the mineral that defines most pottery clays, also serves as the primary source of alumina in many glaze recipes.
Reading Recipes More Confidently
When learning glaze chemistry, ask three questions first:
- What is melting this glaze? (fluxes)
- What is forming glass? (silica)
- What is controlling movement? (alumina sources)
This framework helps you troubleshoot rather than copy recipes blindly.
Pro Tip
Make one controlled change at a time. If you change multiple materials at once, you cannot tell which variable caused the result.
