"Glass with a spongy appearance, with a great many air bubbles, to the point that it is almost opaque. The homogeneous and refined molten mass (with no air bubbles or impurities) is vigorously mixed in with salts (generally sodium carbonate or bicarbonate) that decompose due to the heat and liberate gases (carbon dioxide) dispersed in the form of bubbles of varying diameters."
- from the Murano Glossary on the 20th Century Glass website
