Steel types explained
There are two questions hiding in “which steel”. One is about sound. The other is about how much of your life you want to spend wiping an instrument down.
They have different answers, and it is worth separating them.
The three materials#
These are genuinely different materials, not three finishes on one material.
Raw carbon steel#
Untreated low carbon deep-drawing steel — usually DC04 — with nothing done to the surface beyond perhaps oil or paint.
It is soft, which makes it forgiving to hammer and quick to tune, and it gives a warm, slightly dark tone. It will also rust if you leave a fingerprint on it overnight in a humid room. Very few makers sell raw instruments as a mainstream product.
For a first instrument: avoid. Not because it sounds bad, but because learning an instrument and simultaneously learning to fight corrosion is a miserable combination, and because the cheap end of the market uses raw steel under powder coating precisely to hide what it is.
Nitrided steel#
The historical mainstream, going back to PANArt. The finished shell is held in a nitrogen-rich atmosphere at roughly 500–580 °C so nitrogen diffuses into the surface and forms hard iron nitrides. The result is a hard, dark grey to blue-black skin over a still-ductile core.
The clever part is that this runs below the temperature at which the steel would change phase, so there is no quench and almost no distortion — essential when your workpiece is a 1 mm hemisphere that has to stay round. The hardening is a surface effect, so the core stays soft enough to take a hammer.
Sound: percussive, ceramic, sometimes described as gong-like. A defined attack and a decay that is shorter and cleaner than stainless. Good note separation.
Rust: much better than raw, but this is a coating, not an alloy. Scratch through it, or leave sweat on it, and rust can start. The industry has become notably more candid about this — one well known maker withdrew their rust-free guarantee on nitrided DC04 in late 2023, saying plainly that buyers may encounter rust spots despite protective measures. That is honesty, not a defect.
The blue-black colour on many nitrided instruments comes from a post-oxidation step, not from the nitriding itself.
Stainless steel#
Typically AISI 430 or a maker’s proprietary variant. It resists corrosion through the chromium in the alloy rather than through a surface layer, so a scratch heals itself. Virtually rustproof in ordinary conditions.
Sound: usually longer sustaining, brighter, with a softer attack and more harmonic layering. Critics of the brighter grades describe them as tinny or wild, and long sustain has a real cost: notes overlap more, so fast rhythmic playing can turn into a wash.
“Ember Steel”#
Ember Steel is a stainless formulation introduced by Ayasa Instruments in 2020, positioned between conventional nitrided DC04 and ordinary 430 stainless. It needs substantially higher annealing temperatures than nitrided work, which makes it a more demanding material to build with. The claimed character is long but controlled sustain with good note isolation — longer than nitrided, less wild than plain stainless. It does not rust in normal use and does not need oiling.
How the steel actually changes the sound#
The underlying mechanism is internal damping. Every time the steel flexes, a fraction of the energy becomes heat inside the metal rather than sound in the air. Alloys and heat treatments that lose less energy per cycle ring longer.
| Attack | Decay | Character | Suits | |
|---|---|---|---|---|
| Nitrided | Crisp, defined | Shorter, clean | Percussive, ceramic, dry, focused | Rhythmic and fast playing, where notes need to get out of each other’s way |
| Stainless (430) | Softer, smoother | Long | Warm, layered, bright | Slow, meditative, ambient playing |
| Ember and similar | Moderate | Long but controlled | Fuller and less metallic than plain stainless | Most things; a genuine middle path |
| Raw | Soft | Short in practice | Warm, dark | Rarely left untreated long enough to matter |
Which should you buy?#
For this school and for most beginners: nitrided or a good stainless. Either is right.
Choose nitrided if you are drawn to rhythmic playing, want notes to articulate cleanly and separately, and do not mind wiping the instrument down after each session and oiling it occasionally.
Choose stainless or Ember if you want long sustain, play slowly and ambiently, live somewhere humid or coastal, have sweaty hands, or simply know yourself well enough to know you will not maintain anything.
Since this curriculum teaches rhythm from lesson one, I have a mild preference for nitrided. It is genuinely mild. Do not let it override an instrument that sounds better to you.
Which rusts, and how badly#
The difference is where the protection lives. Stainless protects itself through its bulk chemistry: chromium forms a self-repairing passive oxide film, so a scratch heals. Nitriding protects through a surface layer. Break the layer and the ordinary low carbon steel underneath behaves like ordinary low carbon steel.
In practice, nitrided instruments are fine for most owners in most climates if they are wiped down after playing and oiled occasionally. The situations that cause trouble are consistent:
What actually causes rust
- Sweaty hands, especially salty sweat, left on the surface after a session.
- Coastal air. Salt-laden humidity attacks nitrided surfaces persistently.
- Condensation from bringing a cold instrument into a warm room and shutting it in a case.
- Water pooling inside the shell through the gu — the part nobody inspects.
- Wear at the ding and at the note centres where hands repeatedly land, slowly polishing the hardened layer away.
Stainless owners are not entirely exempt: ferritic stainless can pick up surface staining from iron particles or hard water, which looks like rust but sits on top of an intact surface and usually cleans off.
The one thing that damages every type is neglecting the inside. Air moves in and out of the gu constantly, moisture comes with it, and there is no easy way to wipe the interior. Storing the instrument port-down in a dry place, and never sealing a damp instrument in a case, does more good than any oil.
Oils, lacquers and paint#
Oils are the standard maintenance layer for nitrided and raw instruments: a molecular film that keeps water and sweat off the steel. The technique points that matter are that the film should be very thin, applied to a clean dry surface, and buffed off rather than left sitting. A thick oil layer collects dust, goes gummy, and audibly damps the high partials.
Which specific oil is genuinely contested, and it is a topic where confident advice outruns evidence. Follow your maker’s recommendation, because they know what their surface treatment tolerates.
Lacquers and clear coats applied by the maker at the factory are generally fine. Applying one yourself is a bad idea: coating thickness has a direct acoustic cost, uneven application detunes fields unevenly, and most coatings cannot be removed later without abrasives that will take the tuning with them.
Paint on tone fields adds mass and damping, flattens the notes and shortens sustain. A maker who paints and then tunes has accounted for it. Paint added after tuning has not been accounted for at all — which brings us back to the airbrushed £200 discs on the marketplace.
The general principle: any layer you add is part of the vibrating system.
How thick is the steel, and does it matter?#
Most shells start from sheet somewhere around 0.8 to 1.25 mm, with about 1 mm the common reference point.
It matters for four reasons: thicker sheet is stiffer, so a given pitch needs a larger field; hammering spends thickness, so thinner sheet leaves the tuner less room to correct partials and less headroom for a future retune; thicker sheet generally sustains longer; and thickness is one of the main levers on weight.
Do not read thickness as a quality metric. It is a design choice made in combination with steel type, shell size and target scale. A maker who has settled on 0.9 mm for a high-register instrument has probably thought about it more carefully than someone quoting a number as a selling point.
How can I tell what my instrument is made of?#
Ask the maker, and check your paperwork. There is no reliable home test.
What does help:
- Documentation. Most reputable makers state the material on the invoice, the product page, or a tuning report. This is the primary source and it is usually right.
- Colour and finish. Nitrided is typically dark grey to blue-black, sometimes with a faint blue or purple sheen. Stainless is usually a lighter, greyer, more metallic silver. Suggestive, not proof.
- Rust behaviour over time. The most decisive everyday evidence. Small orange spots where your hands sit means carbon steel with a surface treatment.
If the instrument is secondhand with no history and the maker is unknown, treat it as nitrided for care purposes: wipe it after playing, oil it occasionally. That regime is harmless on stainless and necessary on everything else.
Next#
One more spec decision, and it is the one with the most nonsense written about it.