Selection & Application of Materials & Equipment for Ceramics Flashcards

What is the main reason nepheline syenite is preferred over potassium feldspar as a flux in some studio glaze recipes?

Answer: It melts at a lower temperature, making it suitable for mid-range firing

Nepheline syenite has a lower melting point than potassium feldspar and provides effective fluxing action at mid-fire (cone 5-6) temperatures.

When applying wax resist to a ceramic piece before glazing, what is the primary function of the wax?

Answer: To repel glaze from specific areas, creating unglazed or design patterns

Wax resist repels water-based glaze, leaving those areas bare or maintaining an underlying glaze layer, allowing the ceramist to create defined design areas.

Which raw material is the primary source of alumina (Al₂O₃) in most ceramic glaze recipes?

Answer: Feldspar and kaolin

Feldspar and kaolin are the dominant alumina sources in glaze recipes; alumina from these materials increases viscosity, durability, and firing range.

What is the significance of the 'quartz inversion' at approximately 573°C during a ceramic firing cycle?

Answer: Quartz crystals undergo a sudden volume change that can crack ware if heated or cooled too quickly

At 573°C, alpha-quartz converts to beta-quartz with an abrupt 2% volume expansion; rapid temperature change through this point causes thermal shock and cracking.

When formulating a clay body for a wood-firing kiln, which property is most important to optimize for fly ash glaze accumulation?

Answer: Sufficient surface texture and porosity to hold fly ash deposits

Wood-fired ware benefits from a slightly open, textured surface that catches and holds fly ash deposits, which flux and form natural ash glazes during long firings.

A ceramist applies an underglaze decoration and then a transparent overglaze. What is the correct firing sequence?

Answer: Apply underglaze to greenware → fire to bisque → apply overglaze → fire to glaze temperature

Underglaze applied to greenware is set during bisque firing, providing a stable base onto which transparent overglaze is applied before the final glaze firing.

Which type of glaze application method is most suitable for achieving a very even, thin coat on complex sculptural forms with undercuts?

Answer: Spraying with an airbrush or spray gun

Spraying allows the ceramist to direct glaze onto recessed and undercut surfaces that dipping or pouring cannot reach evenly, giving precise control on complex forms.