--- title: "Cracked French top plate" description: "La Cornue cracked French top plate — a crack in the plaque is neither cosmetic nor automatically terminal, and the difference matters because a replacement…" url: "https://la-cornuemiami.support/symptoms/cracked-french-top-plate/" date_modified: "2026-09-03" Appliance type: "Cooktops and rangetops, Ranges, Rangetops" --- # La Cornue cracked French top plate ### Tell crazing from a crack Let the plate go completely cold and clean it back with a dry brush. Crazing is a fine spider web in the black seasoning layer, it does not catch a fingernail, and it is the normal appearance of a well-used plate. A crack is a single line, usually running from an edge or from the hot center outwards, it catches a nail, and it often shows a rust line along it because moisture has got in. If you can photograph it cold and clean, that photograph is genuinely useful to us. ### 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** — A large plate has more thermal gradient across it and takes the most punishment. Most cracks we see are here. - **Château with a petite plaque** — Smaller, more even, and less prone. A crack in a petite plaque usually has an identifiable event behind it. - **CornuFé** — No plaque on the factory-built models. ### What we can and cannot do about it A stabilized hairline at the edge of a plate, away from the hot center, on a range that is otherwise sound: that is something to monitor, keep dry and season, and it can go on for years. A crack through the center, or one that has opened enough to show light or rust along its length, is a plate at the end of its service life. We will tell you which one you have and we will not tell you it is fine when it is not — but nor will we condemn a plate because it has a line on it, which on this make is an expensive mistake to make on somebody’s behalf. ### Ordering a plate The plaque is part of a made-to-order cooktop configuration, so a replacement is ordered against the range’s own size and configuration code — a large plaque for a K3 Château 150 is not a catalog line you pick off a shelf. Expect a lead time, and expect us to quote it before ordering rather than after. In the meantime the rest of the top is usable, and that is worth knowing: this is one module of several on a range that has plenty of other ways to cook. Thermal shock A wet cloth, a pan of cold liquid or a wash-down on a hot plate. The most common cause and the most preventable. A burner running too hot in one spot A rich or misaligned flame concentrates heat where the plate was designed to spread it. Cast iron is hard and brittle. A dropped stockpot on a cold plate does this. Long-term rust from the underside Corrosion thins the iron until a normal thermal cycle finishes it. Age and cycles Some plates simply reach the end of a long life, and on a range from the 1990s that is a fair outcome. Let it go cold first Everything about this assessment is wrong on a warm plate, including whether the line is even there. Run a fingernail across it Crazing does not catch. A crack does. Look for a rust line Moisture in a crack leaves a trace. It is the clearest confirmation there is. Stop using it if it is through A cracked plate can move, and a moving plate on a lit burner is not worth the risk. A line across the iron What it usually means Crazing in the seasoning is not a crack in the iron Thermal shock is the usual cause — a wet cloth on a hot plate A replacement plate is a made-to-order part, so this gets looked at properly Tell crazing from a crack Let the plate go completely cold and clean it back with a dry brush. Crazing is a fine spider web in the black seasoning layer, it does not catch a fingernail, and it is the normal appearance of a well-used plate. A crack is a single line, usually running from an edge or from the hot center outwards, it catches a nail, and it often shows a rust line along it because moisture has got in. If you can photograph it cold and clean, that photograph is genuinely useful to us. 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 — A large plate has more thermal gradient across it and takes the most punishment. Most cracks we see are here. Château with a petite plaque — Smaller, more even, and less prone. A crack in a petite plaque usually has an identifiable event behind it. CornuFé — No plaque on the factory-built models. What we can and cannot do about it A stabilized hairline at the edge of a plate, away from the hot center, on a range that is otherwise sound: that is something to monitor, keep dry and season, and it can go on for years. A crack through the center, or one that has opened enough to show light or rust along its length, is a plate at the end of its service life. We will tell you which one you have and we will not tell you it is fine when it is not — but nor will we condemn a plate because it has a line on it, which on this make is an expensive mistake to make on somebody’s behalf. Ordering a plate The plaque is part of a made-to-order cooktop configuration, so a replacement is ordered against the range’s own size and configuration code — a large plaque for a K3 Château 150 is not a catalog line you pick off a shelf. Expect a lead time, and expect us to quote it before ordering rather than after. In the meantime the rest of the top is usable, and that is worth knowing: this is one module of several on a range that has plenty of other ways to cook. ### Can a cracked cast-iron plate be welded? In principle cast iron can be repaired, and in practice we do not recommend it here. A plaque is a precision-flat thermal surface that has to sit down onto its seat and conduct evenly across its whole area; a weld introduces a hard zone with different expansion behavior, and the repair usually distorts the flatness that makes the plate work. You end up with the uneven-heating page instead of this one. On a plate near the end of its life we say so honestly and quote the replacement. ### How do I stop it happening to the new one? Three rules and they are not onerous. Never put anything wet on a hot plate — no cloths, no cold liquids, no washing it down until it has cooled. Let it come up and cool down on its own time rather than forcing either. And keep it seasoned and dry, particularly around the edges and underneath, because rust is what turns a normal thermal cycle into a crack after twenty years. That is the whole of it. --- **[Read full article: Cracked French top plate](https://la-cornuemiami.support/symptoms/cracked-french-top-plate/)**