Crackling Wooden Wick Capillary Flow, Pyrolysis & Memory-Ring Engineering Runbook

1. Capillary Transport Physics in Hardwood Xylem Channels

Unlike braided cotton wicks (which rely on inter-fiber spaces and chemical borax/salt treatments), FtaaE's untreated FSC-certified wooden wicks transport liquid beeswax upward through natural longitudinal xylem vessels and tracheids (r ≈ 25–40 μm).

The vertical capillary mass transport rate is governed by the Lucas–Washburn equation:

# Capillary Rise & Mass Flux Model for Beeswax-Coconut Matrix in Wooden Wick Xylem
import math

def capillary_velocity(pore_radius_m: float, surface_tension_n_m: float,
                       contact_angle_deg: float, viscosity_pa_s: float,
                       char_height_m: float) -> float:
    """
    Calculates upward liquid wax velocity v = (r * gamma * cos(theta)) / (4 * eta * h)
    """
    theta_rad = math.radians(contact_angle_deg)
    return (pore_radius_m * surface_tension_n_m * math.cos(theta_rad)) / (4.0 * viscosity_pa_s * char_height_m)

# FtaaE 8 oz Vessel Operating Point @ 58°C Melt Pool:
# r = 32e-6 m, gamma = 0.028 N/m, theta = 18 deg, eta = 0.0098 Pa*s
v_optimal_trim = capillary_velocity(32e-6, 0.028, 18.0, 0.0098, 0.0047) # 3/16" (4.7 mm)
v_untrimmed    = capillary_velocity(32e-6, 0.028, 18.0, 0.0098, 0.0110) # 7/16" (11.0 mm)
print(f"Upward Wax Velocity @ 3/16 in trim: {v_optimal_trim*1000:.2f} mm/s")
print(f"Upward Wax Velocity @ untrimmed:    {v_untrimmed*1000:.2f} mm/s (57% drop -> flame starvation)")

2. Diagnostic Troubleshooting Matrix for Wooden Wicks

| Symptom Observed | Root Physical Cause | Immediate Corrective Action |

| :--- | :--- | :--- |

| Flame extinguishes 5–10 min after lighting | Excess top char (> 6 mm) blocks capillary wax transport to the flame zone | Allow wax to cool, pinch/trim brittle char down to 3/16" (4.7 mm), and relight |

| Peripheral wax ring ("Tunneling") on vessel wall | First burn was extinguished before the melt pool reached the glass perimeter | Wrap upper vessel rim loosely in aluminum foil tent for 45 min to radiated heat evenly across top surface |

| Audible acoustic crackle is faint | Melt pool is still warming up or ambient draft is deflecting flame laminar boundary | Keep away from HVAC vents; acoustic micro-steam expansion peaks once melt pool reaches 4–6 mm depth |

| Wick mushrooms or smokes slightly | Wick was left untrimmed or burned continuously beyond the 4-hour maximum session | Extinguish with snuffer, cool completely, trim to 3/16", and limit each burn session to 4 hours max |

3. Standard Burn Test Verification Checklist (ASTM F2417)

• Pre-trim wooden wick to 3/16" (4.7 mm) above the solid beeswax surface prior to ignition.
• Burn continuously for 3.0 hours on Cycle 1 to verify full-diameter melt pool (depth: 6–10 mm).
• Verify maximum flame height remains below 45 mm (well under the 76.2 mm ASTM F2417 ceiling).
• Discontinue burning when 1/2" (12.7 mm) of unmelted wax remains at the vessel base.