The Second Golden Age of Glass

The Second Golden Age of Glass

At the start of the Second Golden Age of Glass, around 1000 AD, Venice established itself as the main centre for glass making in Europe.

Over time, Venetian glass blowers set up a sophisticated guild system and perfected Cristallo glass which was almost transparent and could be blown to extreme thinness, enabling them to produce objects of extreme delicacy.

The Venetian merchant fleet brought back Syrian and Islamic expertise and at its height over 8,000 craftsmen worked in the Venetian Glass Industry.

However, the furnaces caused numerous fires and eventually all the glassworks were transferred to the Island of Murano which also made it easier to protect the glass makers secrets.

Venetian Cristallo Glass Flask

 

The early method of creating sheet glass

Creating the First Sheet Glass

During the 11th. century, German craftsmen developed the first effective technique for producing flat, sheet glass starting by swinging a hollow glass sphere vertically while the glass was still hot.  Gravity would then draw the sphere into an elongated balloon shape up to 3m in length and 0.5m width. The ends would be cut off and the cylindrical pod cut down the narrow centres to create 2 sheets of glass which could be worked and laid almost flat.

 

 

 

 

 

 

 

The German technique was further refined by the Venetians over the next 100 years or so, during which time major buildings such as Royal Palaces, Cathedrals and Churches had glass windows fitted, sparking the huge surge in popularity of stained glass windows.  As the middle ages drew to a close most Churches, Palaces and the homes of wealthy individuals had stained glass windows decorated with religious scenes or coats of arms and crests.

 

Crystal Glass and Lead Crystal

In the second half of the 15th. century, glass makers on Murano started using quartz sand and potash made from sea plants to produce an especially clear, pure crystal glass.

In response, the English glassmaker, George Ravenscroft, was commissioned to find a substitute to emulate the new pure crystal glass and he is credited with the creation of Lead Crystal using higher amounts of Lead Oxide to produce it.

This brilliantly clear glass with a high refractive index had the added benefit of being easy to engrave and cut and was patented by Ravenscroft in 1674.  

Ravencrofts invention made possible significant development of optical lenses and lenses for microscopes and telescopes.

Lead crystal bowl cut and engraved

 

 

French mirror from the Napoleonic era

French Mirror Makers

Around the same time, French glass makers perfected a technique for producing superior and attractive mirrors.

They poured molten glass on to a special table before grinding it with increasingly fine abrasives before coating one side with a soft, reflective metal surface.  For the first time, mirrors could be created without substantial distortions.

With advances coming thick and fast in glass making centres in Venice, Bohemia, France Germany, Britain and the United States, it was inevitable that glass making would be affected by the industrial revolution.

Increasing commercial uses and the drive to cut costs led inexorably to the industrialisation of the glass making process.