Textures of Clear Glass
Some consider it the most basic colour of glass, some the most precious: Clear glass. People value it for its pure and transparent qualities as well as being an excellent refractor of light and thus it is famously used for crystal chandeliers.
The basis of all hand blown glass is a melted mixture of silica (quartz/sand), lime and sodium which when cooled down results in a transparent material. However, this glass is not simply colourless by default but often shows hues between green and blue. They are caused due to the naturally occurring iron in the sand. Also other impurities from the production process such as metal bits from the glassblowing pipe, air pockets or streaks become particularily noticable in clear glass. To create truely clear glass requires tremendous skills and knowledge.
However impurities during the creation also led to a range of interesting types of glass. For example, when ‘black bottle glass’ was first produced in 17th Century England, the glass was melted by burning coal. The sulfur from the smoke caused a dark brown or green glass colour. An earlier example is obsidian, a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth. It contains impurities that give it a black colour. Nowadays glassmakers create different colours of glass by intentionally adding various minerals and elements to clear molten glass.
When working with pure clear glass, experimenting with its texture is particularly interesting. Apart from its clean and glossy characteristics, the appearance of clear glass can be altered in its hot as well as cold state in nearly endless ways.
Alone the shape and material of the mould into which glass is blown opens up numerous possibilities. Handblown glass of rotational shape is traditionally produced by using watered wooden moulds which ensure a smooth and glossy glass surface. However if the mould is made from metal and the glassblower does not rotate their pipe, the interaction of glass and metal results in an organic, wrinkled surface. Glassmakers also use metal moulds when imposing decorative, haptically perceptible patterns to a body of glass, such as stripes, cricles or diamonds. If they blow glass into other materials such as meshes, they, too, leave haptic and visual marks on the glass‘s surface.
Another way to change the appearance of clear glass is to intentionally create air bubbles inside the hot glass. It gives it a lively texture and results in one-of-a-kind pieces. When interacting with light, for example in a lamp shade, the air bubbles create a special sparkling effect in the glass. A more extreme form of this texture is created by introducing metal dust to the hot glass. Depending on the type of metal, it can colour the glass (see above) and cause air bubbles as well as streaks to appear in a wild manner.
Also after the glass has cooled down, it can still be shaped. Engraving and glass cutting are one of the most traditional techniques to enrich clear glass. The possibilites range from geometric patterns to filigree drawings. Younger techniques are sandblasting to achieve a matte surface and metal coating for a mirroring or iridiscent effect.
The list goes on and on and will surely only get longer in the future, after all experimenting with glass and with clear glass in particular has fascinated people for centuries.
Photography: Vojtěch Veškrna, Bet Orten, Martin Chum