In glassblowing, cane refers to rods of glass with color; these rods can be simple, containing a single color, or they can be complex and contain strands of one or several colors in pattern. Caneworking refers to the process of making cane, and also to the use of pieces of cane, lengthwise, in the blowing process to add intricate, often spiral, patterns and stripes to vessels or other blown glass objects. Cane is also used to make murrine (singular murrina, sometimes called mosaic glass), thin discs cut from the cane in cross-section that are also added to blown or hot-worked objects. A particular form of murrine glasswork is millefiori ("thousand flowers"), in which many murrine with a flower-like or star-shaped cross-section are included in a blown glass piece.
Caneworking is an ancient technique, first invented in southern Italy in the second half of the third century BC, and elaborately developed centuries later on the Italian island of Murano.
Making cane
There are several different methods of making cane. In each, the fundamental technique is the same: a lump of glass, often containing some pattern of colored and clear glass, is heated in a furnace (glory hole) and then pulled, by means of a long metal rod (punty) attached at each end. As the glass is stretched out, it retains whatever cross-sectional pattern was in the original lump, but narrows quite uniformly along its length (due to the skill of the glassblowers doing the pulling, aided by the fact that if the glass becomes narrower at some point along the length, it cools more there and thus becomes stiffer). Cane is usually pulled until it reaches roughly the diameter of a pencil, when, depending on the size of the original lump, it may be anywhere from one to fifty feet in length. After cooling, it is broken into sections usually from four to six inches long, which can then be used in making more complex canes or in other glassblowing techniques.
The simplest cane, called vetro a fili (glass with threads) is clear glass with one or more threads of colored (often white) glass running its length. It is commonly made by heating and shaping a chunk of clear, white, or colored glass on the end of a punty, and then gathering molten clear glass over the color by dipping the punty in a furnace containing the clear glass. After the desired amount of clear glass is surrounding the color, this cylinder of hot glass is then shaped, cooled and heated until uniform in shape and temperature. Simultaneously an assistant prepares a 'post' which is another punty with a small platform of clear glass on the end. The post is pressed against the end of the hot cylinder of glass to connect them, and the glassblower (or 'gaffer') and assistant walk away from each other with the punties, until the cane is stretched to the desired length and diameter. The cane cools within minutes and is cut into small sections.
Variations in cane making
A simple single-thread cane can then be used to make more complex canes. A small bundle of single-thread canes can be heated until they fuse, or heated canes, laid parallel, can be picked up on the circumference of a hot cylinder of clear or colored glass. This bundle, treated just as the chunk of color in the description above, is cased in clear glass and pulled out, forming a vetro a fili cane with multiple threads and perhaps a clear or solid color core. If the cane is twisted as it is pulled, the threads take a spiral shape called vetro a retorti (twisted glass) or zanfirico.
Ballotini is a cane technique in which several vetro a fili canes are picked up while laid side-by-side rather than a bundle, with a clear glass gather over them. This gather is shaped into a cylinder with the canes directed along the axis, so that the canes form a sort of "fence" across the diameter of the cylinder. When this is simultaneously twisted and pulled, the resulting cane has a helix of threads across its thickness.