OK,

Now, the question topic pivots back to either sand or nitre salts as a medium. Would packing the spring in sand, (or the salts) heating, and holding it for a short while in the kiln work? Am I correct in thinking that the spring needs to be quenched at that time? Using either lead, sand or salts as the medium?

I prefer wood to plastic, leather to nylon, waxed cotton to Gore-Tex, and split bamboo to graphite.