bead proof

1. Among distillers, a certain degree of strength in alcoholic liquor, as formerly ascertained by the floating or sinking of glass globules of different specific gravities thrown into it; now ascertained by more accurate meters. [ 1913 Webster ]

2. A degree of strength in alcoholic liquor as shown by beads or small bubbles remaining on its surface, or at the side of the glass, when shaken. [ 1913 Webster ]