IFX-001 · 12 in skillet · Direct sear

Preheat window of a 12 in skillet: 5, 8 or 11 minutes

One 12 in skillet, one burner setting, one oil. The only thing changed was how long the empty pan sat on the heat, and the difference in browning time was 45 seconds.

By The Skillet Desk · Published 14 Aug 2026 · 9 min read

01Abstract

A 12 in cast-iron skillet was preheated on the same medium-high gas setting for 5, 8 and 11 minutes, with surface temperature logged every minute by infrared thermometer. A 180 g flat iron steak was then seared in avocado oil at each temperature and the time to first persistent brown colour recorded. Surface temperature went 300 °F at 2 min, 430 °F at 6 min and 455 °F at 11 min; browning time fell from 140 s to 95 s to 88 s. Past 6 minutes the pan gains 25 °F but the steak gains 7 seconds, while the polymerised seasoning layer takes visibly more heat stress.

02Variables

Independent

Preheat duration: 5 min, 8 min or 11 min at a fixed dial position
Recorded surface temperature at the moment the meat went in

Held constant

Pan: bare cast iron, 12 in, 2.2 in wall, no enamel
Burner: gas, outer ring only, dial held at the 6-of-10 mark
Oil: avocado, 1 tsp, added after preheat and swirled for 5 s
Steak: 180 g flat iron, 22 °C core, patted dry, salted 40 min before
Aim point: infrared gun at pan centre, 2 cm in from the rim

Hypothesis A 12 in skillet keeps climbing past 5 minutes, but the extra surface temperature buys less browning time than the seasoning layer pays for.

03Process

Wipe the cold pan with a dry cloth and set it on the outer ring at the 6-of-10 mark. Start the timer and do not move the pan.
At 2, 4, 6, 8 and 11 minutes, take an infrared reading at the centre of the cooking surface and write it down. Aim from 20 cm and hold the gun perpendicular.
At the chosen minute, add 1 tsp avocado oil and swirl for 5 s; it should ripple and thin out immediately without smoking hard.
Lay the steak down away from you and start a second timer. Do not press and do not move it for 90 s.
Flip at 90 s, 150 s and 195 s cumulative (the 90/60/45 rhythm), then pull to a rack and rest 6 min before slicing.

04Observations

5 min preheat: the oil moved slowly, the steak stuck at two points and left a pale grey ring; first real colour only at 140 s.
8 min preheat: oil thinned in under 2 s, the steak released by itself at the first flip, colour at 95 s.
11 min preheat: colour at 88 s, but the pan smoked lightly at the edges 40 s after the meat went in even with a 520 °F oil, and the seasoning dulled to a matte grey-brown.
The handle was already too hot to hold bare at 5 minutes; at 8 minutes a folded dry towel was needed.
Pan temperature at the 2 cm ring read 20–35 °F cooler than centre at every point, which is why the steak was placed centre-first.

Instrument log

Preheat	Surface at meat-in	Oil behaviour	First colour	Seasoning after
5 min	392 °F / 200 °C	slow ripple	140 s	unchanged, glossy
6 min	430 °F / 221 °C	thins in 2 s	95 s	unchanged, glossy
8 min	441 °F / 227 °C	thins at once	101 s	slight matte patch
11 min	455 °F / 235 °C	smokes at edges	88 s	matte grey-brown, needs re-oil

05Conclusion

Six minutes at the 6-of-10 mark on a 4.2 kW gas ring is the useful ceiling for this pan. Between 6 and 11 minutes the surface only gains 25 °F and browning gains 7 seconds, but the polymerised layer visibly dulls and takes on the grey matte look of a stressed seasoning. If your burner is smaller, preheat to the temperature — 430 °F at the centre — not to the clock: the same 6 minutes on a 2.6 kW ring reached only 385 °F.

Cautions

A cast-iron handle reaches 200 °C+ in 6 minutes. Have a dry folded towel or a leather sleeve ready before you start.
Never plunge a 430 °F pan into water to cool it; thermal shock can bow a thin-walled pan permanently.
If the oil smokes hard within seconds of going in, the pan is past the oil's smoke point. Pull it off the heat for 60 s before adding food.

Clean & season

Let the pan cool on the hob until it can be touched with a bare hand, about 20 minutes.
Scrape residue with a stiff nylon brush under hot running water; no soap is needed and no soaking.
Dry it on the hob over low heat for 2 minutes, then wipe a 1/2 tsp film of the same avocado oil across the cooking surface with a paper towel.
Store it open, not stacked, so air reaches the surface; a damp cabinet is what produces flash rust.

To reproduce

Log the surface temperature at the moment the meat goes in; 430 °F ±10 °F is the target.
Same pan size and same burner ring position; changing to the small ring is a different experiment.
Dry the meat surface and salt 40 minutes ahead, otherwise the first 30 s of the sear is spent boiling water.