Very early on, gunsmiths would immerse a wrought iron spring in molten lead, then quickly quench it in linseed oil. The spring was then placed over heat to temper it. The gunsmith gauged the amount of tempering by the color, yellow, then violet, then blue. Pale blue was used in tempering springs.

This can be seen in the video, "Gunsmith of Colonial Williamsburg" with Wallace Gusler.

Pete

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