Texes Art EC-12 Practice Exam

What oxide is primarily used to achieve blue or metallic tones in ceramic glazes?

1. Cobalt Oxide

2. Iron Oxide

3. Silica

4. Alumina

The correct answer is: Cobalt Oxide

Cobalt oxide is primarily used in ceramic glazes to achieve blue or metallic tones due to its strong coloring properties. When added to glazes, cobalt oxide produces vibrant shades of blue, which can vary from a deep royal blue to a lighter sky blue depending on the concentration used and the firing temperature. Cobalt ions interact with the glass-forming materials in the glaze during the firing process, leading to the characteristic blue hues that artists and ceramists often seek. The versatility of cobalt oxide allows it to be used in various glaze formulations, making it a staple in ceramics for achieving those specific colors. Other oxides, such as iron oxide, tend to produce a range of reds, browns, and earthy tones rather than blue, while silica and alumina primarily act as glass formers and thickening agents in glazes, rather than colorants. Thus, these materials do not contribute to the blue tones desired in ceramic work as effectively as cobalt oxide does.