Glassblowing, Techniques and Equipment
The Raw Material
There are many recipes for making glass. At Jerpoint we have our own special glass recipe, to produce the highest quality glassware. Our recipe or “batch” has thirteen ingredients, 50% of which is silica sand. Other ingredients include potash, lime and borax. The batch is melted into molten glass in the furnace at about 1430oC.
Colour
The colour is made from chipped glass, which has had an oxidant added to it. The oxidant reacts with the glass and causes it to become pigmented. For example, greens and aqua glasses usually have iron. Light blues require copper, while amethyst glass contains manganese. Some reds and pinks even have a bit of gold in them! The glassblower dips their globule of hot glass into a tray of colour. Once it is added to the glass, they fuse together to create the distinctive Jerpoint colours.
Blowing Iron
There are three types of irons used in glassblowing. 1. The blowing iron is hollow and thicker at one end. It is hollow to allow the glassblowers to blow the shape into the molten glass. 2. The bit iron is used to bring gathers of molten glass from the furnace. 3. The glasses are transferred from the blowing iron onto the pontil iron so that we can finish each piece by hand. This strengthens the rim of the glass and also gives us the pontil mark found on the end of each glass. This is the hallmark of a truly handmade glass.
Tongs and Pincers
Tongs and pincers are used to develop the glass, to fix handles and to form the spout on jugs. They are also used to guide the colour patterns, to manipulate the shape of the glass and to open out the piece by hand.
Foot tool
The foot tool is used to shape the feet on the glasses or stemmed bowls. When a globule of hot glass is added to the stem, it is flattened out and formed with this tool.
Other simple tools
Cylinder pipes to blow cool air onto the glass. Blowtorches are used to smooth out the pontil mark, and wooden blocks to even off the shape of the glass.
Furnace
The raw material is melted in the 1400oC oven, turning it into molten glass. Constantly running at temperatures over 1000oC, the furnace keeps the glass in a liquid state until the glassblower is ready to transform it into the Jerpoint designs.
Leher
Once a glass is formed it is placed in the Leher. It gradually cools over night to anneal the glassware, thus removing stress from the piece, solidifying and toughening it.
Glory Hole
The glory hole is a mini furnace used to heat up the piece during its development to allow the glassblower to manipulate the shape.