The 4 components that makes a glaze

Table of Contents

What makes a 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 4 components that make a glaze

Flux – this is the melting agent
Glass formers
Stabilizers
Colorants

A ceramic glaze is usually a receipt of different types of inorganic materials grained to powder, mixed with water to a creamy consistency, and applied with a brush, dipped, or sprayed on the surface of bisque-fired ceramics. So fired a second time (known as the glaze firing), where the components melts on the ceramics, and transforms into a hard and durable coat on top of the ceramic surface.

There are quite few unique ceramic raw materials, but mixed in countless combinations resulting in an endless myriad of glaze recipes, something ceramists often generously share with others. Not only the receipt; but also the firing temperature, the kiln atmosphere, the glaze thickness, and many other factors influence the final result.
Ceramics is glazed for aesthetic and decorative reasons, and to make ceramic wares water-tight and food-safe.

More about glazes in Wikipedia: https://en.wikipedia.org/wiki/Ceramic_glaze

The 4 key components that makes a glaze:

Fluxes – the melting agent

Flux is the reason why we can sinter clay and melting 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.

My 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) (considered by some more as a colorant)
6 – Potassium(K)
7 – Strontium(Sr)
8 – Sodium(Na)
9 – Zink(Zn)

Read more about these fluxing agents here, and why I chose them as the 9 primary raw-material fluxes for ceramics:

9 Important fluxes for ceramics

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 the 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 ceramics.

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.

The 4 components that makes a glaze, also read:

9 Important fluxes for ceramics

Ceramic materials and glaze ingredients