Diamond air trap

Glass Dictionary

Decoration consisting of bubbles of air trapped in the glass in a diamond-shaped pattern. This is achieved by blowing a gather of glass into a mold with projections of the desired design, withdrawing it, and covering it with a second gather, which traps pockets of air in the indentations. This technique was patented by W. H., B. & J. Richardson of England in 1857.

Alternate Spellings: 
Diamond air traps