Antique glass
Antique glass is mouth-blown sheet glass. The word describes the method, not the age: new antique glass is still made today in much the same way as it has been for centuries. A glassblower blows a cylinder or a disc, which is then opened and flattened into a sheet.
It is easy to recognise. The surface has slight ripples, the thickness varies, and small bubbles or streaks of colour are often visible. These irregularities make light sparkle as it passes through, and they are the reason antique glass is prized for church windows and for restoration work, where new glass must sit beside old.
Antique glass is more expensive than machine-rolled glass and the sheets are usually smaller, but the depth and variation of colour are difficult to match any other way.