Two phrases dominate stainless cookware marketing, and between them they leave out the specification that matters most.
18/10 is the alloy of the surface that touches your food. Tri-ply is how many layers the pan is built from. Neither tells you how thick the conductive core is — and that thickness is what decides whether the pan heats evenly, holds its temperature, and stays flat for twenty years.
Decoding the numbers
18/10, 18/8 and 18/0 are chromium and nickel percentages.
| Grade | Chromium | Nickel | Structure | Where it is used |
|---|---|---|---|---|
| 18/10 (304) | 18% | 10% | Austenitic — non-magnetic | Cooking surface. Most corrosion-resistant of the three. |
| 18/8 (304) | 18% | 8% | Austenitic — non-magnetic | Cooking surface. Essentially the same grade family as 18/10. |
| 18/0 (430) | 18% | ~0% | Ferritic — magnetic | Base exterior, so an induction hob can couple with it |
Chromium is what makes steel stainless: it forms a thin, self-repairing chromium oxide layer that protects the metal underneath. Nickel improves corrosion resistance further, adds toughness, and produces the austenitic structure — which happens to be non-magnetic, which is why a good stainless pan needs a separate ferritic layer on its base for induction.
The practical difference between 18/10 and 18/8 in a domestic pan is small. The difference between either and 18/0 on a cooking surface is not: 18/0 is more prone to staining and pitting, particularly with salt. If a pan’s interior is 18/0, that is a cost decision.
Why stainless needs help with heat
Stainless steel conducts heat at roughly 16 W/m·K. Aluminum manages about 235 and copper about 400. A pan made of stainless alone develops hot spots in the shape of your burner, because heat cannot spread sideways fast enough to even out.
Every good stainless pan therefore contains something else. The layer count tells you how:
Tri-ply (3-ply): 18/10 interior, aluminum core, magnetic stainless exterior. The standard construction, and entirely sufficient when the core is thick.
5-ply: usually alternating stainless and aluminum layers, sometimes with copper. More layers sound better and are not automatically so — five thin layers can total less conductive metal than three thick ones. Count matters less than total core thickness.
Copper core: higher conductivity than aluminum, heavier, considerably more expensive. A genuine improvement in responsiveness, with diminishing returns for everyday cooking.
Disc-bottom (impact-bonded): a stainless body with a conductive disc bonded to the base only. The walls are plain stainless. Fine for boiling and stock; poor for anything cooked up the sides, like a risotto or a reduction.
Fully clad vs disc-bottom: how to tell
This is the construction difference you can feel, and manufacturers do not always state it plainly.
- Look at the rim. On a fully clad pan the layers are visible as a sandwich at the cut edge.
- Look at the base from the side. A disc-bottom pan usually has a visible step or lip where the disc is attached. Fully clad construction runs smoothly from base to wall.
- Feel the wall weight. Fully clad walls are noticeably heavier and thicker than a thin stainless shell.
- Read for \”fully clad\” or \”clad through the walls\”, as opposed to \”encapsulated base\” or \”impact-bonded base\”, which mean disc.
The specification to look for
Where a manufacturer publishes total base thickness in millimeters, that figure predicts the pan’s behavior better than ply count, grade or price. Under about 2 mm total and the pan will be quick but twitchy and prone to warping; around 2.5 to 3 mm is the sweet spot for most domestic cooking; above that you are buying thermal mass, which is useful for searing and tiring to lift.
If no thickness is stated, weight is a usable proxy. Between two pans of the same diameter and construction, the heavier one has more metal in it.
Why food sticks, and what to do about it
Stainless steel is not a release surface, and nothing will make it one. But most sticking is a heat-control problem rather than a property of the metal.
Protein sticks when it meets metal that is not hot enough: the surface bonds to the steel before a crust can form. Preheat properly and the crust forms first, and the food releases when it is ready.
The water test. Heat the dry pan over medium heat, then flick in a few drops of water. If they sizzle and evaporate, it is not hot enough. If they form beads that skitter across the surface like mercury, the pan is at the right temperature. Add fat, then food. The beading happens because a vapor layer forms under the droplet and lifts it off the metal, and it is a reliable visual indicator of surface temperature that requires no thermometer.
Two more rules. Let food sit — moving it before a crust forms tears it and leaves protein on the pan. And do not crowd the pan: too much cold food at once collapses the surface temperature and you steam instead of browning.
Unlike a nonstick pan, a stainless pan should be preheated empty. There is no coating to damage, and dry preheating is how you get it to the right temperature.
Discoloration: three kinds, three causes
Rainbow or oily-looking iridescence. The chromium oxide layer thickening with heat, which creates interference colors in the same way oil on water does. Entirely harmless and purely cosmetic. A mild acid will remove it — white vinegar on a cloth usually does.
Chalky white spots or a film. Calcium and other minerals from your water, left behind by evaporation. Harmless. Vinegar removes it, and it recurs if your water is hard.
Brown or blue-black stuck-on residue. Polymerized oil and burnt food, which is the one that needs actual work. A commercial oxalic acid cleaning powder is the usual answer. Simmering water with a little dish soap loosens most of it first, which means less scrubbing.
What to avoid: steel wool and abrasive scouring pads, which scratch the surface and give food more to grip; chlorine bleach, which attacks the chromium oxide layer and can cause pitting; and leaving salt sitting in a dry pan, which also pits.
Where stainless beats everything else
Its real advantage is not thermal, it is chemical. Stainless steel is effectively inert, so acidic food does nothing to it. A tomato sauce, a wine reduction, a lemon pan sauce, a vinegar deglaze — all fine, indefinitely. Cast iron and carbon steel cannot do that without stripping their seasoning, and nonstick coatings do not like it either.
It is also effectively permanent. Oven-safe to high temperatures, broiler-safe with a metal handle, dishwasher-safe, metal-utensil-safe, and able to be scrubbed hard. A clad stainless pan bought well is a thirty-year purchase, which is why it is the sensible thing to spend money on.
And being inert and smooth, it shows you what you have made. Fond — the browned residue on the base after searing — is visible, and deglazing it is how a pan sauce happens. On a nonstick surface, fond barely forms.
What to look for, in order
- Fully clad, not disc-bottom, unless the pan is only ever going to boil water.
- Base thickness around 2.5 to 3 mm, or the heavier of two similar pans.
- 18/10 or 18/8 interior.
- A magnetic exterior base if you have or may have induction — test it with a magnet.
- A riveted or well-welded handle, and a stated oven temperature rating.
- A flat base, checked with a straight edge.
- Helper handle on anything 12 inches or larger — a clad pan that size is heavy when full.
Related guides
- Cookware materials explained
- Cast iron vs carbon steel
- Will it work on induction?
- Which pans you actually need
Alloy compositions, the austenitic and ferritic structures, and the role of the chromium oxide layer are established metallurgy. Thermal conductivity figures are nominal published values for the standard materials, not measurements of specific pans. Base thickness ranges above are practical guidance rather than a tested threshold.