boiling-out

Updated: June 6, 2025

I draw the temper in the following manner: Place some fine brass filings in a boiling-out cup or bluing pan and lay the blank upon these filings, holding the pan over the flame of an alcohol lamp until the blank assumes a dark purple color, which it will reach when the heat gets to about 500° F. This I consider the right hardness for a balance staff, as it is not too hard to work well under the graver nor too soft for the pivots.

Eugene Edward Hall - A Treatise on Staff Making and Pivoting : Containing Complete Directions for Making and Fitting New Staffs from the Raw Material