Carbon steel or stainless steel?
Nearly every precision blade you can buy is one of two steels, and the choice between them is a single trade repeated in different words: carbon steel gets sharper, stainless steel survives neglect.
Everything below is detail on that sentence.
What actually differs
Carbon steel is iron with carbon in it, typically between 0.05 and 2.1 per cent. That carbon is what lets the steel be hardened, and hardness is what lets an edge be ground fine and stay fine.
Stainless steel is the same thing with at least 10.5 per cent chromium added. The chromium forms an invisible oxide layer on the surface that re-forms when scratched, and that layer is the entire reason stainless does not rust. Some grades add nickel or molybdenum to push that further.
The chromium is not free. It occupies space in the alloy that carbon would otherwise use, which is why stainless is generally a little softer and why the two behave differently at the edge.
Sharpness
Carbon steel takes a finer edge and holds it longer. On a blade ground to a few micrometres that difference is genuinely noticeable: a carbon blade parts card and film cleanly where a stainless one of the same shape starts to push.
Stainless is not blunt. It is slightly less keen out of the packet and it dulls a little sooner. For most work that gap is smaller than the gap between a fresh blade and one you have been using for an hour, which is worth keeping in proportion.
Corrosion
This is where the order reverses, and not by a small margin.
Carbon steel has essentially no corrosion resistance. Left damp, or simply left in a humid room after being handled, it will begin to rust within hours at the edge, long before anything is visible on the body of the blade. In Britain that is not an edge case, it is most of the year.
Stainless will sit in the same drawer and be fine. That is the whole of its appeal, and for a lot of people it is decisive.
Brittleness
Harder also means more brittle. A high-carbon blade under sideways load is more likely to snap than to bend, which matters if you twist a blade in a cut or lever with the tip.
Stainless is slightly softer and correspondingly tougher, so it tends to flex where carbon would break. If you have ever snapped the point off a fine blade, that is the property you were missing.
So which
| If this is you | Buy |
|---|---|
| You cut in sessions and put tools away properly | Carbon |
| The finish of the cut is the finished surface | Carbon |
| Your workspace is a garage, shed or unheated studio | Stainless |
| Tools live loose in a drawer or a toolbox | Stainless |
| You work around water, clay or plaster | Stainless |
| You go through blades quickly anyway | Carbon |
| You snap fine points regularly | Stainless |
Two honest observations on that table. If you replace blades often, carbon is the obvious answer, because corrosion resistance protects a blade over a lifespan you are not using. And if you are unsure, buy stainless: a slightly less keen blade that works is better than a keener one that has gone off in a drawer.
The same blade in both steels
You can test this without taking anyone's word for it. The #11 double honed blade is the standard fine carbon blade. The #21 stainless blade is the same fine profile in stainless. Same handle, same cut, two steels, and the difference is yours to judge on your own materials.
Whichever you choose, how you store it matters more than which you bought. Our guide on keeping blades from rusting covers the storage and oiling that makes carbon steel entirely practical, and makes stainless last longer than it otherwise would.