Gardens of Glass: Chihuly at Kew

How Glass Is Made

Although glass is hard and solid, it starts as liquid. There are many different methods of making glass - it can be pressed, cut, moulded or formed by glassblowing.

First, the glassworkers mix sand, soda and lime in a melting pot. This mixture is called a batch and becomes as thick as honey when it's hot. The batch is heated to over 2,000 degrees Fahrenheit, about as hot as a volcano. When the batch is ready, a hollow metal rod, called a blowpipe, is dipped into the tank to get a clump of glass.

Next, the glass is shaped using callipers or small glass-working tools, cut with shears and rolled or flattened out over a bench. The glass is coloured using very condensed colour rods, powders or frit (small pieces of glass) to achieve different effects.

Then, the glassblower twirls the blowpipe while blowing into it. The hot air makes the clump grow into a bubble. While the glass is being shaped, it has to be reheated in a furnace, called a glory-hole, or with a blowtorch. If it cools too quickly, it will break. When the piece is finished, the glassworker puts it into an annealing oven where it is gradually cooled over several hours to several days.

Chihuly uses clear soda-lime based glass, made up of a very clear sand, with a variety of fluxes to do a variety of tasks. These include making the glass more homogenous, as well as making the glass clearer and bubble free. It assists the glass to become softer and stay hotter so there is more working time at bench or on a man-lift. A good working temperature for this formula is around 1226 Celsius.

As Chihuly Over Venice unfolded, Dale Chihuly developed the idea of blowing glass vertically from a man-lift, as opposed to the traditional method of working on a bench. This vertical glass blowing technique enables the team to create large pieces such as Reeds and Herons , which stand up to 3-4 meters high. The size of these pieces means the team is challenged with extra weight, gravity, proper heating and timing, as the pieces cannot be re-heated in the Gloryhole. This vertical glass blowing technique is a key part of the scale achieved in Chihuly's large outdoor installations.