The Science Behind Ru Ware's Frost Veins ("Crackle Patterns")

1. Fundamental Causes

- Thermal Stress:

  • Clay (α=5.4×10⁻⁶/°C) & glaze (α=7.1×10⁻⁶/°C) coefficient mismatch

  • Generated during cooling from 1300°C→200°C at ~15°C/min rate

- Crystalline Growth:

  • Mullite (3Al₂O₃·2SiO₂) needles form at 1100-1250°C

  • Agate particles create localized stress points

2. Formation Process

Stage 1 (Firing):

  • 0-900°C: Clay body shrinks 8%, glaze remains fluid

  • 900-1300°C: Glaze melts, encapsulates agate particles

Stage 2 (Cooling):

  • 1300→800°C: Primary cracks form (50-200μm wide)

  • 800→200°C: Secondary branching occurs (10-30μm)

Stage 3 (Aging):

  • Years 1-5: Tea tannins deposit in cracks (0.01mm/year)

  • Years 5+: Iron oxidation darkens veins (Fe₂O₃ migration)

3. Unique Characteristics

- Directionality:

  • 75°-110° branching angles (determined by quartz content)

  • Never intersects glaze bubbles (Φ<0.2mm)

- Acoustics:

  • Crack density affects sound frequency (280-320Hz ideal)

  • Dull "thud" indicates over-cracked inferior pieces

4. Modern Quality Standards

- A-grade:

  • 3-5 main veins/cm² with dendritic branches

  • Vein depth = 0.1-0.3×glaze thickness

- Reject criteria:

  • Cracks reaching clay body

  • Symmetrical "spiderweb" patterns (indicates artificial quenching)

5. Distinguishing Features

- Natural vs. Artificial:

  • Authentic: Veins follow agate distribution (random but logical)

  • Fake: Uniform depth/length (acid-etched)