FERETTO, (Encycl.) Another way of making feretto is as follows. Make a number of stratifications of plates of copper and white vitriol alternately in a crucible; which place on the floor of the glass furnace near the eye; and let it stand there three days; then take it out, and make a new stratification with more fresh vitriol; calcine again as before. Repeat this operation six times, and a most valuable feretto will be obtained.