Ola Höglund of Höglund Art Glass, With Pipe
History of Glass
- Before people learned to make glass, it was made by nature, in two ways. When lightening strikes sand, it sometimes fuses it into slender glass tubes called fulgurites. Volcanic eruptions also sometimes fuse rocks and sand into a glass called obsidian. Early people shaped obsidian into various objects, including adornments, weapons, and money.
- According to legend, man first made glass about 2000 BC. Phoenician sailors set up a camp on the sandy beach of a river in Syria and built a fireplace to support the cooking pots for their evening meal, using pieces of sodium carbonate found in their cargo from Egypt. The next morning they discovered that the sodium had fused with the sand and formed clumps of a clear substance – glass.
- In truth, it is not known exactly where or when people learned to make glass. It is believed that the first intentionally created glass was used as a glaze on ceramics earlier than 3000 B.C., but it wasn't until around 1500 B.C. that glass vessels began to appear in Egypt. The popularity of glass manufacturing rose and fell for hundreds of years until it became a strongly established commodity around 500 B.C.
- Making glass in these early days was difficult and expensive, as glass blowing and pressing had not been discovered yet, clay vessels used for melting the glass were not of good quality, and it was difficult to generate sufficient heat to facilitate melting.
- Eventually, glassmakers learned to make colored glass and began to create glass jewelry, and tiny vessels, which were considered as precious as fine jewels!
- The blowpipe was invented around 30 B.C. This phenomenal invention was a revolutionary event in the history of glass making. The tools and techniques used to form molten glass have changed very little over the centuries.
- The craft of glassblowing was passed from father to son, and from master to apprentice. From its beginnings, the formulas and procedures used in glassmaking were closely guarded. At times in history, the penalty for disclosing secret techniques was death!
Quick Glassblowing Facts
(provided by Höglund Art Glass)
- Glassblowing is done in the same way today, as it was in medieval times with the same type of tools.
- Glassblowing is an art that takes years and years to master. In the old days an apprenticeship was 15 years. The glassblower has to spend all his working life practicing his techniques. A glassblower will never be “fully trained”.
- A glass furnace has to be built especially to suit each glass studio’s specific needs.
- The three glass furnaces at the Nelson glassblowing studio are based on traditional Swedish design, and are built of very specialized bricks and materials from France and the USA, that can withstand the heat of +1800 degrees Celsius (+3304 degrees Fahrenheit) .
- The newest glass furnace at the Nelson studio, was built in 2002. After completion, it had to dry out for 6 months before it could be fired to melting temperature. The largest furnace is a tank furnace. It is built like a tub which holds the molten glass inside the furnace.
- We have two pot furnaces. This means the molten glass sits in a ceramic pot inside these furnaces. These are very specialized ceramic pots, built by hand in Germany. They are shipped to New Zealand in the “raw" state, meaning that they are not fired until we have placed them inside the furnace. Each pot holds 250 kg of molten glass, and is used for 6 months before it is changed for a new pot. Changing the pots this often, enables our studio to have the best quality glass possible.
- Each time we change the pot, we have to turn off the furnace for approx 4 weeks, to enable the furnace to first cool down enough to be handled. The front of the furnace has to be taken off brick by brick for us to reach the old pot, remove it and replace it with a new one. The glass furnace then has to be heated up VERY SLOWLY over a period of approximately 14 days. We increase the temperature approximately 100 degrees Celsius (212 degrees Fahrenheit) per day, and after 14 days the furnace is up to a temperature of +1420 degrees Celsius (+2620 degrees Fahrenheit) and the pot is ready to be fired.
- After the firing of the pot, it has to be glazed. This is done with molten glass from the other furnace. After the firing and glazing, the temperature is taken down to +1360 degrees Celsius (+2512 degrees Fahrenheit) and the first batch of glass can be melted.
- The furnaces continue to burn day and night.
- It takes just as long to take the furnace down in temperature as it takes to get it up. That is why we never turn a glass furnace off except for the pot changes.
- We use 80 tonnes of LPG gas per year.
- The working temperature of the glass in the furnace is + 1150 degrees Celsius (+2134 degrees Fahrenheit). The glass at that temperature has a texture of runny honey and the glassblower has to roll the pipe at all times or the glass will fall off the pipe.
- The glass needs to be soft and pliable to enable the glassblower to shape and blow it into its final shape.
- The temperature of the glass while being worked on the blowpipe is approx. +700-1000 degrees Celsius (+1292-1832 degrees Fahrenheit).
Other Tools, Equipment, and Techniques
(provided by Höglund Art Glass)
- Blow Pipe: The hollow stainless steel pipe used to blow the initial bubble
- Punty Rod: A solid rod which goes onto the other end of the piece for shaping the opening
- Wet, Wooden Paddles: For shaping
- Wet Cork Paddles: For shaping
- Wet Newspaper: For shaping.
A layer of steam builds up between the surface of the wet paper and the hot glass, which allows the glassblower to hand-shape the glass without getting burned.
- Wet Wooden Block: For shaping the very hot gather of glowing glass into a symmetrical form. These are usually made from cherry wood or other fruit wood (which burns slowly and holds water well).
- Jacks: The glassblower's most essential tool. The design has not changed in the past 2000 years. Jacks are used to "cut" the hot glass and to shape and sculpture.
- Shears: To cut and trim hot glass.
- Glory Hole: A gas fired drum-shaped chamber used for heating and re-heating glass, which is on a glassblowing pipe or a punty rod. The glory hole is kept running only during work hours and is turned off during the night. Glass is reheated in the glory hole to keep it at the right working temperature.
- Annealing Kiln: An electric, insulated kiln where the finished glass objects are placed upon completion of the hot process. The temperature in the annealing kiln is +500 degrees Celsius (+932 degrees Fahrenheit) which is the same temperature as the finished piece. Any hotter, and the piece will collapse and lose shape. Any cooler, and the piece will crack. At the end of the day it is gradually taken down to room temperature over 48 hours, to relieve thermal strain and stress within the glass.
- What is made in a day will be ready in 48 hours.
What is Crystal?
(provided by Höglund Art Glass)
- Crystal Glass has either lead or barium added to give it a sparkling, clear quality.
- The lead or barium also makes glass soft for cutting and engraving.
- Different mixes are suitable for different products. For example, lead crystal glass is very sensitive and not suitable for vases, wine goblets or salad bowls.
- The lead in the crystal can leave a ‘matt film’ on the glass when it comes in contact with water.
- The first clear, transparent glass was produced in Rome, around the first century A.D.
- By 1500 the Venetians had developed Cristallo - soda glass with added lime from crushed marble or seashells, and manganese as a decolouriser. This glass was lightweight, and could be blown very thin.
- In England around 1675 George Ravenscoft perfected the manufacture of a revolutionary lead crystal glass. By adding lead oxide to the glass, he produced a whiter, softer glass with a greater refractive brilliance than any of its predecessors.
- Today crystal glass can be made with the same qualities of the lead crystal glass, replacing the lead with barium and other substances and we call this lead free crystal glass.
- Crystal glass produced by Höglund Art Glass, is lead-free crystal glass.