Blue steel springs are the traditional type, as opposed to stainless steel. They might be liable to rust, but are superior to stainless steel and give a good response without being sluggish, and are found on most good quality instruments.

Although the bluing does help to prevent rust, it is actually an essential part of the process and is certainly not just a finish. Let me explain:- High carbon steel can be heat treated. It is first heated to red-heat and quenched. This makes the previously soft steel very hard, but it is also very brittle and of little use. It is further heat-treated to a lower temperature, which gradually brings down the hardness and reduces the brittleness. The higher the temperature the softer and less brittle it becomes, until it is eventually in its former soft (annealed) state. As the temperature is increased, the steel changes colour, going from straw to brown and then blue - so the colour is an indication of how far the heating (tempering) process has gone.

The colour and degree of tempering will be governed by the steels final use, so knives, for example, would be straw as they need a keen edge, but bend it and it would break (it is harder but also brittle). Obviously if clarinet springs were tempered the same as knives they would be useless as they would break. The correct temper for springs is blue. They are still fairly hard, but can be bent without breaking. The blue colour is left on for three reasons:

1. it looks nice.
2. it shows it has been correctly hardened and tempered.
3. it helps to prevent rust.

Finally, it is the same as "regular" steel. Stainless-steel would never be described as "regular".

From Brian Ackerman, ackerman@mistral.co.uk
Posted to Klarinet: Mon, 1 Sep 1997

(A note from the Webmaster):
Blueing as applied to gunsmithing is very different. Blueing a gun involves a liquid which creates a preservative coating on the steel. It does not change the hardness of the steel in any significant way, and is not, in my experience, used for clarinets. In any case, the literature for the clarinet would say "blued steel", not "blue steel".