Selection & Application of Materials & Equipment for Ceramics Flashcards

Which type of kiln atmosphere is essential when firing reduction glazes to achieve metallic luster effects?

Answer: Reduction atmosphere

Reduction atmospheres limit oxygen, causing iron and copper oxides in glazes to lose oxygen and produce metallic, iridescent surfaces.

What is the primary purpose of adding silica (flint) to a clay body?

Answer: Control thermal expansion and add strength

Silica acts as a structural filler that controls thermal expansion coefficients and contributes to the fired strength of the ceramic body.

A ceramist notices crazing in a glaze after cooling. What is the most likely cause?

Answer: Glaze thermal expansion is too high relative to the clay body

Crazing occurs when glaze contracts more than the clay body on cooling, placing the glaze in tension and causing fine cracks.

Which equipment is used to measure the specific gravity of a glaze slop to ensure consistent application thickness?

Answer: Hydrometer

A hydrometer measures the specific gravity of a glaze slop, which directly relates to the water-to-material ratio and resulting coat thickness.

When selecting a kiln wash, which property is most critical to prevent glaze from bonding to kiln shelves?

Answer: Non-adhesive surface at high temperatures

Kiln wash must remain non-adhesive and non-reactive with molten glaze at peak firing temperatures to allow easy removal of ware.

What does LOI (Loss on Ignition) measure in ceramic raw materials?

Answer: Weight lost as gases and water during firing

LOI is the percentage of weight lost when a material is heated to high temperature as water, carbon dioxide, and organic matter are driven off.

Which type of extruder die is best suited for producing hollow cylindrical ceramic forms?

Answer: Spider die

A spider die has a central mandrel supported by arms (spiders), creating a hollow passage through the extruded ceramic column.