Spring-Smithing was originally a branch of the Blacksmith's Trade-Skills.
A Spring-Smith is the Person who Puts The Force of Resilience into the Pre-Formed-Spring-Shape :
By Heating It; and Cooling It Very Slowly:
In a very-care-fully-controlled-manner.
The Traditional Method was to heat the forged mild steel up to a pale-cherry-red colour; and Immersing it in almost-boiling oil;which was then Very Slowly Cooled in a pit; in a packed-straw or hay-insulated box; which was then covered in HOT SAND to retain the heat.
A fire would then be lit on top of the sand, to keep it hot for a week, or as long as required.

WARNING !!! Especially At The Moment Of Immersion :
THIS TRADITIONAL METHOD INCLUDES A HIGH FIRE RISK.

It Should Only Ever Be Attempted Out-Doors, By Professionals, who have Good Fire-Fighting equipment nearby, and the skills to use it Safely.

When you eat dirt for the first time and leave your family to build a shack in the woods