Ceramic Glaze Quiz

Fused Coating on Ceramic Objects:

• Ceramic glaze is a glassy coating on ceramics that is used for decoration and to make the item impermeable to liquids and pollutants.
• Glazing makes earthenware impermeable to water and gives a tougher surface, and is also used on stoneware and porcelain.
• Glazes may form a variety of surface finishes, including degrees of glossy or matte finish and color, and may enhance the underlying design or texture either unmodified or inscribed, carved or painted.
• The most important groups of traditional glazes, each named after its main ceramic fluxing agent, are lead, tin, and salt.
• Glaze may be applied by spraying, dipping, trailing, or brushing on an aqueous suspension of the unfired glaze.
• Historically, glazing of ceramics developed rather slowly, as appropriate materials needed to be discovered, and also firing technology able to reliably reach the necessary temperatures was needed.
• Glaze components are more likely to be leached into the environment when non-recycled ceramic products are exposed to warm or acidic water.
• Lead(II) oxide (PbO) is used primarily as a flux for its low melting range, wide firing range, low surface tension, high index of refraction, and resistance to devitrification.
• Barium carbonate (BaCO3) is used to create a unique glaze color known as barium blue, and is also somewhat soluble in acid, and can contaminate water and soil for long periods of time.
• Chromium(III) oxide (Cr2O3) is used as a colorant in ceramic glazes, and can undergo a reaction with calcium oxide (CaO) and atmospheric oxygen in temperatures reached by a kiln to produce calcium chromate (CaCrO4).
• Urania-based ceramic glazes are dark green or black when fired in a reduction or when UO2 is used; more commonly, it is used in oxidation to produce bright yellow, orange, and red glazes.
• Ceramic industries are reluctant to use lead alternatives since leaded glazes provide products with a brilliant shine and smooth surface.