CCE Selection & Application of Materials & Equipment for Ceramics 2 — Questions and Answers
Question 1: Which type of kiln atmosphere is essential when firing reduction glazes to achieve metallic luster effects?
- Oxidation atmosphere
- Reduction atmosphere (Correct answer)
- Neutral atmosphere
- Inert atmosphere
Correct answer: Reduction atmosphere
Reduction atmospheres limit oxygen, causing iron and copper oxides in glazes to lose oxygen and produce metallic, iridescent surfaces.
Question 2: What is the primary purpose of adding silica (flint) to a clay body?
- Increase plasticity
- Lower the firing temperature
- Control thermal expansion and add strength (Correct answer)
- Improve green strength
Correct 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.
Question 3: A ceramist notices crazing in a glaze after cooling. What is the most likely cause?
- Glaze thermal expansion is too low relative to the clay body
- Glaze thermal expansion is too high relative to the clay body (Correct answer)
- Firing temperature was too low
- Clay body was too porous
Correct 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.
Question 4: Which equipment is used to measure the specific gravity of a glaze slop to ensure consistent application thickness?
- Pyrometer
- Hydrometer (Correct answer)
- Viscometer
- Refractometer
Correct 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.
Question 5: When selecting a kiln wash, which property is most critical to prevent glaze from bonding to kiln shelves?
- High thermal conductivity
- Non-adhesive surface at high temperatures (Correct answer)
- Low alumina content
- High flux content
Correct 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.
Question 6: What does LOI (Loss on Ignition) measure in ceramic raw materials?
- The amount of free silica in the material
- Weight lost as gases and water during firing (Correct answer)
- Thermal expansion of the material
- The flux content of the material
Correct 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.
Question 7: Which type of extruder die is best suited for producing hollow cylindrical ceramic forms?
- Flat die
- Spider die (Correct answer)
- Ribbon die
- Screen die
Correct answer: Spider die
A spider die has a central mandrel supported by arms (spiders), creating a hollow passage through the extruded ceramic column.
CCE Selection & Application of Materials & Equipment for Ceramics 2
Which type of kiln atmosphere is essential when firing reduction glazes to achieve metallic luster effects?