Glossary
Quick answer
32 plain definitions for the cookware and knife terms that come up when buying. Clad means bonded layers of different metals. Seasoning is oil polymerised onto bare iron by heat. Honing straightens a rolled edge while sharpening removes metal to make a new one.
Definitions written to be quotable on their own. Where a term has a number attached, the number is here too.
| Term | Definition |
|---|---|
| Clad | Cookware built from bonded layers of different metals, typically an aluminium core between stainless faces. "Fully clad" means the layers run up the walls as well as across the base. |
| Disc base | A stainless pan with a thick aluminium or aluminium and steel disc bonded only to the bottom. The walls are plain thin stainless, so sauces can scorch at the waterline. |
| Tri-ply | Three bonded layers: a stainless cooking surface, an aluminium core, and a magnetic stainless exterior so the pan works on induction. |
| Five-ply | Five bonded layers, alternating stainless and aluminium. More even and more stable than tri-ply, and heavier and slower to respond. |
| Thermal conductivity | How fast heat moves through a material, measured in watts per metre-kelvin. Copper is about 401, aluminium 237, cast iron 52, stainless 16. |
| Heat retention | How much energy a pan holds once hot, which comes from mass and specific heat rather than conductivity. It is what stops a pan cooling when cold food lands on it. |
| Specific heat | The energy needed to raise one kilogram of a material by one degree. Iron is about 460 J/kg-K and aluminium about 900. |
| Seasoning | Oil polymerised onto bare iron or steel by heat, forming a hard slick layer. It is maintained rather than permanent, and detergent, dishwashers and long acidic cooking strip it. |
| Fond | The browned residue left on a pan after searing. Deglazing dissolves it into liquid, which is what a pan sauce is made of. Bare stainless builds it best. |
| Reactive | A material that chemically interacts with acidic or alkaline food. Bare cast iron, carbon steel and bare aluminium are reactive; stainless, enamel and glass are not. |
| Ferromagnetic | A metal a magnet sticks to. Induction hobs heat only ferromagnetic bases, which is why a fridge magnet is a definitive compatibility test. |
| Austenitic stainless | Stainless grades such as 18/10, which is grade 304, containing enough nickel to be non-magnetic. Inert and excellent as a cooking surface, and it does not work on induction alone. |
| Ferritic stainless | Magnetic stainless grades such as 430. Used as the exterior layer of clad cookware specifically so induction hobs can couple to the pan. |
| PTFE | Polytetrafluoroethylene, the polymer in most nonstick coatings. It begins breaking down near 500F, and its fumes at that point are rapidly fatal to pet birds. |
| Sol-gel ceramic | A silica-based nonstick coating containing no PTFE. Published oven ceilings are generally lower than PTFE lines and the release typically fades sooner. |
| Vitreous enamel | Glass fused to metal at high temperature. Inert, so acidic braises are safe in it, and it chips if knocked and cracks under thermal shock. |
| Thermal shock | A sudden temperature change across a material. It warps metal bases permanently and cracks enamel, glass and stoneware. A hot pan meeting cold water is the usual cause. |
| Anodising | An electrochemical process that thickens aluminium's natural oxide layer into a hard, much less reactive surface. It is part of the metal and does not peel. |
| Flare loss | The difference between a skillet's rim diameter, which is how it is sold, and its flat cooking surface. On a typical flared skillet it is about two inches. |
| Crowding | Putting more food in a pan than its surface can evaporate moisture from. The food then steams at around the boiling point of water instead of browning. |
| Rockwell C hardness | A hardness scale, written HRC, measured by pressing a diamond cone into steel under a set load. Kitchen knives run roughly 55 to 66 HRC. |
| Edge retention | How long a blade stays sharp in use. It tracks hardness closely, and higher hardness also means the edge chips rather than rolls when it fails. |
| Honing | Straightening an edge that has rolled to one side, usually with a steel or ceramic rod. It removes no metal and is not sharpening. |
| Sharpening | Removing metal on an abrasive to create a new edge. A whetstone sharpens; a rod does not. |
| Powder steel | Steel made by consolidating metal powder, giving a very fine and uniform grain. SG2 and R2 are the common kitchen examples, running about 63 to 64 HRC. |
| Patina | The stable grey oxide layer that forms on carbon steel with use. It is protective and normal, and it is not the same as orange rust. |
| End grain | A board built so the cut ends of the wood fibres face up. The knife edge passes between the fibres and they close behind it, which is the kindest surface to a blade. |
| Edge grain | A board built from long strips laminated side by side. Most of the edge friendliness of end grain, for considerably less money and weight. |
| Half sheet | A sheet pan 18 by 13 inches. The largest size that reliably fits a domestic oven, and what nearly every home recipe means by "sheet pan". |
| Full sheet | A commercial sheet pan 26 by 18 inches. It does not fit a domestic oven, which is usually only 22 to 24 inches wide inside. |
| Standard | On this site, a published material property, manufacturer specification or physical relationship. It does not vary by opinion. |
| Convention | On this site, a widely used kitchen rule of thumb. Useful and defensible, and not a specification. Every page says which of the two it rests on. |
Common questions
What is the difference between clad and disc base?
Clad cookware bonds an aluminium core between stainless layers across the entire vessel, walls included. Disc base bonds a thick aluminium disc to the bottom only, leaving the walls as plain thin stainless. The practical difference shows up when reducing a sauce: a clad pan heats the walls too, while a disc-base pan can scorch at the waterline.
What is the difference between honing and sharpening?
Honing straightens an edge that has rolled over to one side, which is what a steel or ceramic rod does, and it removes no metal. Sharpening removes metal on an abrasive to create an entirely new edge, which is what a whetstone does. Most knives that feel blunt only need honing, and no amount of honing substitutes for eventual sharpening.
What does HRC mean on a knife?
HRC is the Rockwell C hardness scale, measured by pressing a diamond cone into the steel under a set load and reading the indentation depth. Kitchen knives run roughly 55 to 66 HRC. Higher numbers hold an edge longer and chip rather than roll when they fail, which is a genuine trade rather than a straight improvement.
What is fond?
Fond is the browned residue stuck to a pan after searing, and it is almost entirely flavour. Adding liquid and scraping dissolves it, which is what deglazing means and what a pan sauce is built from. Bare stainless builds fond better than any coated surface, which is the main reason to own a clad stainless skillet.
What does reactive mean for cookware?
A reactive material chemically interacts with acidic or alkaline food. Bare cast iron and carbon steel lose their seasoning to long acidic simmering and can leave a metallic taste, and bare aluminium discolours both itself and the food. Stainless, enamel, glass and stoneware are inert, which is why a long tomato braise belongs in one of those.