Working with Glass
Glass-blowing is an exciting yet potentially dangerous activity.
The glass artist is constantly working in an environment with many recognisable hazards. There is the extreme heat of the furnaces; the fluidity of molten glass; even the possibility of the glass shattering or exploding if proper care is not taken in managing its temperature.
These risks inherent in working with hand-blown glass are perhaps the reasons why it is such a beautiful medium. The glass artworks encapsulate a tension between the process of their creation and the fragility of the finished works.
The Glass Working Process
When blowing glass, artists typically begin with a mix of ingredients called "the batch". Just like cooking, this is a recipe of ingredients that add together to form glass. This includes silica (high-grade sand), sodium and potassium carbonate. When melted together in the furnace at temperatures of around 1280 degC they create a basic glass mixture.
Further additives are added to the glass to stabilise the mixture. These additives help reduce bubbles and increase the workability of the molten material by managing physical properties such as viscosity. Additional mineral oxides, such as copper, silver, cobalt, gold, and nickel can be added in order to created coloured glass.
Rob also uses another recipe produced from recycled glass in some of his works. This particular mix is a form of optically brilliant glass, similar to lead crystal. This special glass provides additional clarity and brightness to those artworks that will benefit from it.
Working with molten glass is the primary step in creating a new piece. To do this, the molten glass is gathered on the end of the glass blower’s most important tool, the blowpipe. This gather of glass must be turned constantly or it will drop to the floor like honey from a spoon.
As the hot, pliable glass is exposed to the air it cools gradually and stiffens. The blown glass must be reheated at intervals in a special heating chamber called the glory-hole. The glass artist uses the blowpipe to create a bubble in the glass which is then worked and slowly blown larger. Hand tools, such as cold steel plates, wet newspaper, and wooden blocks are used to shape the formless molten glass as it expands.
Finished pieces are placed in a kiln to be “annealed”; cooled gradually from around 550 C to room temperature. so as to resolve internal stresses and ensure they don’t crack.
Iridised glass displays a satin reflectivity with iridescent colour showing through. For those pieces which will feature an iridised surface, a special process is included during the glass blowing.
A specialty glass containing silver oxide is applied to the exterior surface of the main bubble. Whilst the form is still hot, the nearly completed form is returned to the glory hole. There it undergoes a special heat treatment which converts the silver oxide on the surface to solid silver.
Following this, an iridising solution containing tin oxide is applied to the hot solid silver surface which converts it to a satin iridescent colour.
Cold Glass Work
Once the glass pieces have cooled to room temperature they can be further enhanced via a number of processes. These can include etching, sand-blasting, engraving, or painting directly onto the surfaces of the glass artworks.
For Robert’s work specifically, he has invested in specialised computer and software technology. These allow him to render the complex and painstaking masking required for the final stages of many of his pieces. This process creates the intricate surface details that are characteristic of much of his glass art.
Once the cold work is complete, the pieces are given a final clean and the artworks are ready to display.