Investigation of the effects of luster glazes on chamotte bodies

European Mechanical Science, cilt.9, sa.3, ss.320-327, 2025 (TRDizin)

Luster is a thin metallic film formed on the glaze surface through the migration and reduction of metal ions under

a reducing atmosphere. This film causes optical interference, producing metallic and iridescent color effects. In this study,

silver nitrate (AgNO₃) was used as the luster-forming agent. During reduction, silver ions migrate toward the glaze surface and

are reduced to metallic silver. Glaze formulations containing AgNO₃ and various lead-based and alkaline metal oxides were

prepared and brush-applied onto chamotte clay test tablets biscuit fired at 1000 °C. The glazed samples were first heated to

1000°C in a gas-fired raku kiln over 2 hours to ensure proper glaze maturation. After the firing process was completed, the

tablets were removed with tongs when the kiln temperature dropped to 850°C through free cooling. For the reduction process,

sawdust, newspaper, dried fruit, walnut, and hazelnut shells were prepared in a metal barrel, and the test tablets were placed in

the metal barrel and subjected to reduction for 20 minutes. After the reduction process, samples A and D exhibited gold-brown

effects on the test surfaces, while samples B and C exhibited gold-copper and iridescent rainbow effects. Microstructural

analyses were performed on post-firing samples. The analyses confirmed the presence of Ag and Cu ions on the surface

of samples A, B, C, and D. The chamotte body’s rough and porous structure caused partial glaze absorption, reducing luster

intensity; however, increased glaze thickness improved luster development, while surface roughness contributed a distinctive

textural aesthetic.

Keywords: Luster Glaze; Reduction; Chamotte Clay; Silver Nitrate; Ceramics

oxides are added to the glaze, and the reduction proce