Getting a cluster of micro-crazing returns on 1.67 with premium AR after salt-pan adjustments, and I’m trying to isolate the culprit. We’re keeping exposure under about 60 C and avoiding cold counter rinses, yet I still see star-field patterns along the temporal edge within 48 hours. What temperature control or heating tool has protected your hard coat + hydrophobic stack during precise temple bends?
I ditched the salt and use a thermostat hot‑air warmer; I pre‑warm the lens to about 35–40°C with my palm, heat only the eyewire, pop lenses for temple bends, and keep the lens surface under 45–50°C with an IR gun. If you’re stuck with salt, swap to glass beads plus a digital probe around 55–58°C and keep heat off the area where you saw the “star‑field” on the temporal edge. Think crème brûlée, not stir‑fry.
Same issue here, and what fixed it was a bead bath plus a small aluminum heat sink on the temporal eyewire — think a foil‑wrapped coin clamp — so I can heat the frame at 80–90°C while I “keep the lens under 45°C” with an IR gun. For stubborn temple bends I’ll pop just that lens like @nina_m85 and re-seat after, but if you’re stuck with salt, Kapton tape around the lens edge works as a quick heat dam. Treat 1.67 like crème brûlée: gentle, localized heat or it blisters.
And had that ‘within 48 hours’ star‑field on 1.67 until I started taking another 0.05–0.10 mm off and easing the temporal bevel before any heat, so the lens isn’t pre‑loaded when you warm the eyewire. If you’re stuck with a salt pan around 60°C, a strip of Kapton tape on the temporal edge is a cheap heat shield, or just pop the lens out for the bend and re‑seat to reset tension.
I started doing a gentle ‘anneal’ after any temple/eyewire heat: set the job on a 40–45°C surface for about 2 minutes, then let it drift to room temp, and keep the lens face under about 45°C. A non‑contact thermometer keeps me honest because the bath saying 60°C doesn’t reflect the gradient at the coating; paired with @nashville93’s heat‑sink, it killed my 1.67 premium AR ‘star‑field within 48 hours’ on tight temporals.
I fixed this by measuring “at the lens” with a stick‑on thermochromic dot right on the temporal edge; the salt pan read about 60°C, but that spot was spiking into the 80s from localized contact… @OP a cheap 60/70°C adhesive indicator (e.g., McMaster-Carr) shows it instantly, then you can shave exposure time rather than dropping your whole heat setting.
I switched to a PID‑controlled glycerin bath at 56°C and press a chilled aluminum blocking ring as a heat sink on the temporal edge while warming the eyewire — no crazing on 1.67 since. @clayton_k is right about localized spikes; put a strip of matte black tape there so your IR read isn’t lying.
I stopped seeing those starbursts after switching to a low‑flow hot‑air pencil and working behind a simple foil shield with a thin silicone pad touching the lens — “no cold starts,” so I pre‑warm the whole job to about 35°C and finish the bend in under 5 seconds. If you keep your current rig, at least pre‑temper and keep the heat moving; Zeiss’s care note leans the same direction: https://www.zeiss.com/vision-care/en/help-topics/handling/lenses-care.html.