Venetian glass was so fashionable in Elizabethan England that it was effecting the balance of trade. As a result, in 1575, a law was passed banning its importation. Instead, a monopoly was granted to Jacope Verelini, a Venetian-born glassmaker, to manufacture Venetian-style glass in England.
This Anglo-Venetian glass was fragile, contained microscopic air bubbles and was discoloured in various hues.
In 1615, concern that the burning of wood to make glass was depleting the nation’s forests, led to the passing of a law forbidding its use. In 1623, Sir Robert Mansell, took over the glass monopoly and proceeded to reorganise the entire industry, designing new coal-fired equipment and developing coal mines.
In 1674, George Ravenscroft developed “flint glass” by using silica of calcined flints. This produced a cleaner, heavier glass with greater refractive brilliance.
In the following year, Ravenscroft replaced potash with lead oxide as a flux. This kind of glass is now called “lead crystal”.
For two years Ravenscroft worked to eliminate the tiny cracks, called “crizzling”, which appeared on completed pieces because of imperfect stabilisation of the glass. In 1677, Ravenscroft guaranteed his glass against crizzling. However, almost all surviving examples of his work show signs of this defect.
The earliest English flint glass wares copied European designs; but by 1682, it was found that the amount of glass could be doubled without losing translucency. This led to much more substantial, heavier English designs – particularly goblets with sturdy stems and thick-walled bowls.
At the end of the 17th century the “balluster” wine glass was introduced. Coinciding with the sober, restrained fashions of the Queen Annne period, these glasses were quite tall (up to 30cm) but usually extremely simple in design. They consisted of a deep ovoid bowl on stem with a tru, or inverted, balluster and one or knops. The foot was wide and usually had a folded rim.
The fashion for these heavy ballusters lasted only until the 1720s when smaller, lighter glasses, with knops incorporating air bubbles, became popular.
The introduction of the Perrot furnace in 1734, produced a higher and more uniform temperature than was previously possible. This resulted in a more uniform glass without the dark tinge of earlier glass.
Early flint glass was highly brittle. This was improved in about 1740 by improvements in the annealing process by which the glass is toughened by heating and slow cooling. In 1745 , it was found that double annealing produced a stronger and more brilliant glass. Further improvements to the annealing process were made in about 1780.
As a result of these improvements, from 1740 shallow cutting of the glass was possible. And from 1780, deep cutting was possible.
In 1745 an excise was levied on glass by its weight. As well as producing lighter wares, manufacturers attempted to recoup their costs by introducing decoration wherever possible in order to be able to charge higher prices for their pieces.
This took the from of engraving, cutting, gilding and enamelling.
Decanters with ground glass stoppers came into general use around the 1760s. These were often made in sets and many were gilded with name of the contents and kept in a metal or leather-covered stand.
From this time, the pontil mark (left on the base of the glass by the rod which holds it during blowing) was sometimes removed. After 1780, the pontil mark was always removed.
The desire to produce more decorated glass also led to the production of coloured glass in Bristol. The most characteristic Bristol glass is a rich, deep blue but it may also be purple, green or red. Bristol was also famous for its opaque white glass (which is now very rare). This became popular because of a loophole in the glass excise law which excluded opaque glass. The loophole was closed in 1777 and little white Bristol glass was produced after that date.
A glassworks was opened at Nailsea, a few miles from Bristol, in 1788. This factory took advantage of the fact that the excise on bottle glass was less than that on other glass too make wares from the cheaper material. The output comprised pleasing, but simple, articles for everyday use. The most characteristic articles were made of striped coloured glass. Originally intended for sale at country markets, much of it was exported to America where it served as a model for the glass manufacturers there.
In 1802, new furnaces were developed which produced a much more intense heat which fused the materials in half the time of the older furnaces. This produced a crystalline appearance which is characteristic of nineteenth English century cut glass.