Review & Advanced Fundamentals

Module 1: Review & Advanced Fundamentals

1. Recap of Level 1 Glazing Techniques

Glazing at an intermediate level builds on foundational techniques, ensuring precision and control.

• Dipping: The most efficient method for even coverage, where a piece is submerged in glaze. Key factors include:

• Glaze viscosity (thick enough to coat but not too sticky).

• Dipping duration (longer dips create thicker layers).

• Avoiding drips by shaking off excess gently.

• Pouring: Ideal for interiors or large pieces, where glaze is poured over the surface.

• Rotate the piece to ensure full coverage.

• Control thickness by adjusting pouring speed.

• Brushing: Best for detailed work or touch-ups, requiring smooth, even strokes.

• Multiple thin layers prevent cracking.

• Use soft brushes (e.g., hake brushes) to minimize streaks.

• Glaze Consistency:

• Should resemble heavy cream for dipping/pouring.

• Thicker for brushing (but not clumpy).

• Water can be added to adjust, but too much dilutes glaze stability.

2. Advanced Glaze Chemistry Basics

Understanding glaze chemistry helps predict results and troubleshoot issues.

A. Oxides and Their Effects:
Metallic oxides influence color, texture, and melt behavior:

• Cobalt Oxide (CoO): Strong blue pigment (0.5–2% sufficient for deep hues).

• Iron Oxide (Fe₂O₃): Produces earthy tones (reds, browns, greens) depending on kiln atmosphere.

• Copper Oxide (CuO): Creates greens (oxidation) or reds (reduction firing).

• Manganese Dioxide (MnO₂): Browns/purples; can also encourage speckling.

• Rutile (TiO₂ + Fe): Variegated effects (mottled creams, blues).

B. Glaze Stability and Fit (Thermal Expansion):
A glaze must "fit" the clay body to avoid defects:

• Crazing (Crackled glaze): Caused by glaze shrinking more than clay. Fix by:

• Adding silica (↑ glaze expansion) or reducing alumina.

• Adjusting cooling rate (slower cooling can help).

• Shivering (Glaze flakes off): Glaze shrinks less than clay. Fix by:

• Reducing silica or adding flux (e.g., feldspar).

• Testing Fit: Use coefficient of expansion (COE) calculations or simple test tiles (freeze/heat cycles to check durability).

Key Considerations:

• Fluxes (e.g., soda, potash, boron): Lower melting points but affect expansion.

• Silica (glass former): Provides structure but must balance with fluxes.

• Alumina (stabilizer): Prevents runoff but excess causes stiffness.

This knowledge allows potters to modify commercial glazes or create custom