Ceramic chemistry

Ceramic chemistry (or, more specifically, glaze chemistry) studies the relationship between the physical properties of fired ceramic glazes and their chemistry. Although ceramic technicians have long understood many of these relationships, the advent of computer software to automate the conversion from batch to formula and analysis has brought this science within the reach of many more people. Physical properties of glazes in fired products (like thermal expansion, hardness, index of refraction, color and melting temperature or range) are directly (but not solely) related to the chemistry. Properties of glass melts like viscosity and surface tension are also principally products of chemistry.

Technicians in the ceramic tile, tableware, artware, pottery, sanitaryware, glass, fiberglass, bottle glass, optical and related industries all use this science.

In ceramic chemistry, fired glazes are viewed as composed of oxides (examples are SiO₂, Al₂O₃, B₂O₃, Na₂O, K₂O, CaO, Li₂O, MgO, ZnO, MnO, Fe₂O₃, CoO). Each oxide is known to contribute specific properties to the fired glass. Materials suppliers publish chemical analyses of their products that cite percentages of these oxides as well as volatiles (oxides that burn away during firing like H₂O, CO₂, SO₃).

For example, in traditional ceramics here are some examples of what the application of ceramic chemistry can accomplish.

Fix glaze defects like crazing, blistering, pin-holing, settling, clouding, leaching, crawling, marking, scratching, powdering.
Substitute frits or incorporate better, cheaper materials, replace no-longer-available ones.
Adjust glaze melting temperature, gloss, surface character and colour (in ceramic colour is a matter of chemistry).
Identify weaknesses (e.g. proximity to volatile firing zones, use of unreliable materials) in glazes to avoid problems.
Creating and optimizing base glazes to work with difficult colours or stains and for special effects dependent on opacification, crystallization or variegation.
Create glazes from scratch and use native materials in the highest possible percentage.

In ceramic bodies the physical properties of the final fired product are more related to the firing curve, the physical properties (e.g. particle size and shape, decomposition history) of the ingredient materials and the mineralogy and interaction between the different particle types.

References

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