Bubbles can occur in glass either because the glass-maker intends it, as part of the design, or because the techniques used were so crude that bubbles remain, as sometimes found in very old glass or in the work of novice glassmakers. Hand made glass nearly always has a few small bubbles. Good quality art glass will have only a few, apart from those that are part of the design.
Bubbles as a decorative technique have been used by almost every glassmaker at some stage. They may be random bubbles incorporated into the glass to give it an "ancient" appearance as in "Clutha" glass made by James Couper and Sons of Glasgow towards the end of the nineteenth century. This effect can be achieved by adding chemicals to the glass batch which react to produce random air bubbles during the melting process. The Italian name for the kind of glass with random bubbles is "pulegoso".
Single bubbles may be pushed into molten glass with a spike, making an internal sphere which looks silvered when the glass cools. Tools with rows of spikes have been invented by glassmakers to produce a stream of such bubbles in a line, or a pattern of regular bubbles like those in the picture on the left. The Italian name for glass with a regular pattern of air bubbles is "bullicante".
James Powell's Whitefriars Glassworks produced a whole series of designs with symetrical bubble patterns from the mid-1940's through the 1950's (examples on the left). Italian glass from Murano was produced with bullicante patterns within all kinds of glass objects, from birds and fish and fruit to bowls and dishes, over a long period from the 1930's.
Paperweight bubble vases were produced in many colours in Sweden, some labelled ASEDA, Sweden. The Kosta factory in Sweden also produced bubble glass designs in the 1950's and the two shown above on the left are from Japan.
