Normally when a glass blower take a glob which is called a gather of glass they only have just a few moments to shape it to the form that they desire. Glass Artists or Glass blowers as they are known transform the glob to a work of art in this short time. It may require as many as a hundred trips to the furnace to complete their project. These glass blowers have to be very strong if they are working on a piece of a larger size. Smaller items of course don't require such vigor.
The method of glassblowing that uses a furnace and what is called a glory hole is called "offhand glass blowing". During the middle ages, Venice, Italy became the center of glass making. In order to maintain their virtual trade monopoly on glass, the government forced all the glassblowers in Venice to move to the island of Murano in 1291.
The Murano glassblowers developed an incredibly clear glass called cristalo, along with new vivid colors such as deep blue, amethyst and emerald. Despite the fact that leaving the island was punishable by death, many Venetian glassblowers did manage to escape Murano and spread their new techniques and new colors throughout Europe and parts of Asia.
I have read that due to the endangerment of glass blowers who escaped Murano and tried to use furnaces which could be easly detected during the day that they operated them only at night and then during the day they used what is called the lampworking method to manipulate glass rods and tubes. For this they used a crud type of torch which today has developed in to a modern and very efficient tool for the glass artist.
When originally developed, lampworking used rods and tubes developed through offhand glass blowing. Today, special glass-drawing machines create the rods and tubes used by the lampworking glass artist. Therefore, the glass used by lampworking artists has previously been shaped. With offhand glass blowing, the glass used to create objects has never been made into a specific form. Rather, it is still a molten glob waiting to be shaped by the glass artist.
Lampworking is different from offhand glass blowing, because tubing and a glass rod are heated and softened with a torch and not a furnace. the softened glass is transformed into its final shape. Like the offhand method, lampworking also involves using special hand tools and blowing techniques in order to create the piece. Both practices are also concerned with gravity and the effects it has on the piece as it is being created.
The sculpture below is an example of "Lampwork" at its finest. The sculpture is called "Midnight Shower"