--- title: "French top heats unevenly" description: "La Cornue french top heats unevenly: the plaque coup de feu is meant to be uneven — hottest directly above its single burner and cooler as you work outwards…" url: "https://la-cornuemiami.support/symptoms/french-top-heats-unevenly/" date_modified: "2026-09-03" Appliance type: "Cooktops and rangetops, Ranges, Rangetops" --- # La Cornue french top heats unevenly ### Learn the plate before condemning it Bring the plaque up for twenty minutes and map it with a pan of water or an infrared thermometer: center hottest, edges usable, corners warm. That is correct. If the center is not the hottest point, the burner underneath is the suspect, not the iron. If the whole plate is down evenly, it is the burner again. If one region is dead while the rest behaves, that is when the plate itself is in question. ### What it usually means, by the kind of La Cornue appliance La Cornue sells one appliance in several forms, and the same behavior points at different things on each of them. A built-in side-by-side and an integrated column are not the same service situation, and a dual-fuel range and an induction range fail in different halves. - **Château with a large plaque** — One 7,500 BTU burner under a large plate. The whole surface depends on that single burner, which is why it is checked first. - **Château with a petite plaque** — Same principle, smaller plate, and it comes up to temperature noticeably faster — so a slow petite plaque is a clearer signal. - **CornuFé** — The factory-built models do not carry a plaque. If this is a CornuFé, we are talking about a solid element or a gas burner instead. ### The mistake almost everyone makes with a French top Treating it like a burner. A plaque is a single cast-iron heat reservoir, and it is used by moving pans around it rather than by turning a knob — full heat at the center for searing, a gentle simmer at the edge, and everything in between at once. That means the first question on this call is not what is wrong but what the owner expects, and a proportion of these visits end with a demonstration rather than a repair. We would rather do that than sell somebody a part for a plate that is behaving exactly as La Cornue designed it in 1908. ### What actually goes wrong In order of how often we find it: the burner beneath, the underside of the plate, the air path, the seating, and only then the iron itself. Every one of the first four is recoverable and three of them cost parts of nothing. It is also worth saying what a plaque does not suffer from — there is no element, no sensor, no board and nothing to calibrate. When it is working it will outlive the kitchen it is in. A weak or rich burner underneath The most common finding by a wide margin. A yellow or small flame cannot load a plate this heavy. Scale or rust on the underside The face nobody inspects. It insulates the iron from its own burner. A blocked drip or air path Combustion needs air under the plate, and grease closes it off gradually. A warped plate It no longer sits down onto its seat, so heat crosses an air gap instead of metal. A crack through the iron It interrupts conduction across the plate and it is the one finding that is not adjustable. Give it twenty minutes A plaque judged after five minutes is a plaque judged wrong. It is thermal mass and it works slowly on purpose. Map it deliberately Center, mid, edge. Write the numbers down and the answer usually appears on its own. Look at the flame underneath Blue, even, and the right size. This is where most of these calls are solved. Check that it sits flat A plate rocking on its seat is transferring heat across air. The plaque has cold areas What it usually means Graded heat is the design — a cold center is not Most plate complaints start with the burner underneath Rust and scale on the underside change conduction Learn the plate before condemning it Bring the plaque up for twenty minutes and map it with a pan of water or an infrared thermometer: center hottest, edges usable, corners warm. That is correct. If the center is not the hottest point, the burner underneath is the suspect, not the iron. If the whole plate is down evenly, it is the burner again. If one region is dead while the rest behaves, that is when the plate itself is in question. What it usually means, by the kind of La Cornue appliance La Cornue sells one appliance in several forms, and the same behavior points at different things on each of them. A built-in side-by-side and an integrated column are not the same service situation, and a dual-fuel range and an induction range fail in different halves. Château with a large plaque — One 7,500 BTU burner under a large plate. The whole surface depends on that single burner, which is why it is checked first. Château with a petite plaque — Same principle, smaller plate, and it comes up to temperature noticeably faster — so a slow petite plaque is a clearer signal. CornuFé — The factory-built models do not carry a plaque. If this is a CornuFé, we are talking about a solid element or a gas burner instead. The mistake almost everyone makes with a French top Treating it like a burner. A plaque is a single cast-iron heat reservoir, and it is used by moving pans around it rather than by turning a knob — full heat at the center for searing, a gentle simmer at the edge, and everything in between at once. That means the first question on this call is not what is wrong but what the owner expects, and a proportion of these visits end with a demonstration rather than a repair. We would rather do that than sell somebody a part for a plate that is behaving exactly as La Cornue designed it in 1908. What actually goes wrong In order of how often we find it: the burner beneath, the underside of the plate, the air path, the seating, and only then the iron itself. Every one of the first four is recoverable and three of them cost parts of nothing. It is also worth saying what a plaque does not suffer from — there is no element, no sensor, no board and nothing to calibrate. When it is working it will outlive the kitchen it is in. ### How hot should the center actually get? Hot enough to sear directly on the iron, which in practice means well over 500 °F at the center after a proper preheat, with a usable simmer at the outer edge. We measure it rather than quote a single number, because the honest figure depends on the plate size, the fuel and how long it has been up. What matters diagnostically is the gradient and the ceiling: a plate whose center tops out where its mid-zone used to be has lost its burner, not its iron. ### Should I be seasoning it, and does that affect the heat? Yes, and yes indirectly. Seasoning is what keeps a plaque from rusting and what makes it pleasant to cook on directly; it does not measurably insulate. What does insulate is the opposite — rust and baked-on carbon layers, particularly on the underside where nobody looks. Part of a French top service is cleaning that face back and re-seasoning the top properly, and we will show you how to keep it rather than leaving you to guess. --- **[Read full article: French top heats unevenly](https://la-cornuemiami.support/symptoms/french-top-heats-unevenly/)**