Making Millefiori Paperweights
Using any of the techniques mentioned before, the artist creates hundreds, sometimes thousands, of millefiori for a paperweight. The artist arranges the pieces by hand inside a metal ring and applies a glob of clear molten glass onto the arrangement with a pontil, setting the design. The metal ring not only can withstand the incredible heat of the hot glass, but will also help to keep the design tight and symmetrical. The ring also helps contain the molten clear glass, which acts as a binder as well as a magnifier for the millifiori. A release agent -- which is sort of like the non-stick spray you use in cooking -- keeps the glass from bonding to the metal as the artist works. Many artists preheat the glass chips, which have already cooled as he or she works, on a hot plate before adding the hot, clear glass. Adding molten glass to cool glass chips can cause them to crack and break.
To get the final shape of the paperweight, the artist will use a block -- a sort of wooden spatula. The block is usually made from a fruitwood. Apple, cherry and pear work the best because the dense grain pattern of the wood leaves a smooth finish on the glass. For this part, wood works better than metal, since metal can be heavy and would heat to scalding, making it impossible for the artist to hold onto it. The artist keeps the block soaking in water so that the wood is saturated. The wet block creates a pocket of steam on which the glass moves into a uniform shape.
When the artist is satisfied, he or she will put the final piece into an annealing oven. Set at about 900 degrees (482.2 Celsius), the annealing oven slowly cools down to room temperature over a set period of time. As glass cools, it shrinks and expands. Using an annealing oven helps the artist control the cooling process, preventing the glass from cracking and shattering. Most blown glass pieces, for example, might take about 10 to 12 hours. However, a paperweight, because it's so dense, may take as long as 18 hours to cool completely.