Glassblowing is the art of inflating molten glass into a bubble, a parison, by blowing through a specially designed tube, a blowing iron. The earliest evidence of creating and moulding molten glass comes from 1500bc and has been recovered by archaeologists excavating in Iraq, Syria and Egypt. Glass blowing developed approximately 1000 years later in Syria.
A ‘blowing iron’ is a metal tube with a mouthpiece at the top and a cone at the bottom. The cone is heated before placing in the melting pot. This stops thermal shock shattering solid glass from the irons last use and molten glass will not stick properly to a cold iron. The iron goes into the pot and rests on the surface of the molten glass. It is not forced in as the glass will enter the tube and block it. Twisting the iron gathers a blob of glass. As the iron and its ‘gather’ are removed, the iron is rotated so the gather does not drip.
First the gather is ‘mavered’ by rolling it on a smooth flat surface. The gather can also be shaped by ‘blocking’. Sat in a glassmakers chair, the iron is rolled along the chair arms whilst a block or a wad of wet newspaper is held against the glass. When the gather has been rolled into an egg-like shape, it is blown. The first blow is the hardest as the resulting bubble must be centred on the iron. Blowing is steady and not strained. Even though the blowing has begun, you may have to return to the furnace to reheat, or use a smaller ‘glory hole’ furnace, or gather more glass.
Another way to shape glass
Instead of shaping the glass by hand, a mould can be used. Gather is collected with the blowing iron, it may be prepared with mavering and blowing, but it is then placed in a mould. A mould can be made from metal or wood. Inside a design is carved into the walls. Hinged moulds have two or more parts that are closed around the ‘gather’. A dip mould is a single piece like a cup. When it is inside, blowing continues and the glass is forced into the shape of the design. If it has worked, opening the mould will reveal a complete item. Moulds can greatly speed up production and create patterns that are difficult to achieve with tools.
Making a goblet
There are differences between the approach of a glass artist and a glassworker in a large factory. For both it is a hot, fast and tiring activity.
To make a goblet:
- Blow the glass until the bubble is correct for a bowl.
- Pincers or ‘jacks’, squeeze the glass below the pipe to create a groove.
- A second gather is stuck to the bowl and the jacks draw it out to form a stem.
- A third gather is stuck to the stem and shaped into a foot with a ‘footing board’.
- A solid metal rod, called a ‘puntil iron’ or ‘punty’, is stuck to the bottom of the foot with a small blob of molten glass.
- Filing, with a metal file, the groove created in (2) and then tapping the blowing iron snaps off the goblet.
It now stands the correct way up on the punty. The glass is still soft so the rim can be cut level with shears. This creates a ribbon of waste with a twist in it. Returning to the chair the iron is rolled along the arms and the jacks are squeezed or spread to shape the bowl and rim. Once pleased with the shape, the goblet then needs to cool in the lehr.
Glassblowing demonstrations are available on Saturdays and Sundays from 1.30pm to 3.30pm.
During the school holidays weekday demonstrations are from 11am - 2.30pm and at weekends they are from 12noon to 3.30pm.