Pre-18th century and early Georgian glass
For the early part of the 17th century English glasshouses were predominantly small family-run concerns manufacturing unsophisticated items for domestic or local use. Venetian glassware was coveted by all and sundry, but the export of raw materials and the knowledge of the technology itself from the hive of industry that was glassmaking around the lagoon was supressed to preserve the desirability and exclusivity of the region's exported pieces. The furnaces of the region were shut down each year from August to January and eventually glassmakers received dispensation to leave the city and seek employment elsewhere for the duration of this hiatus. Others chose to risk the fines, conscription and confiscations that were threatened by the City council to keep them in line, and slowly but surely the previously closely-guarded trade secrets began to percolate across Europe and spawn new centres of manufacture - first in other regions of Italy, then in Austria, Bohemia and ultimately in Belgium and London.
The immigrant workers no doubt brought invaluable insight to the English glassmakers, but they remained unable to replicate Venetian finery due in no small part to the lack of top quality raw materials which were readily available to the master craftsmen in Venice. English glass remained discoloured and tainted by the contamination with smoke and soot from coal-fired furnaces, and even when lead was added to the mix to draw out these contaminants and enhance clarity it often resulted in its own residual yellow tinge if saltpetre was not added to the mixture - it was an ongoing balance of trial and error - not quite alchemy in the truest sense of the word, but experimental chemistry in pursuit of a specific prize nonetheless.
Ravenscroft was already prominent amongst London's glassmaking community, had previously moved in Venetian circles whilst trading lace there and was refining his methods of manufacturing the highest quality of water-white crystal glass for the production of mirrors. He enlisted the assistance of several former associates from Italy who were able to expand and enhance his knowledge base and his aggregation of information and persistence eventually paid of when in 1674 he was awarded the patent for his new and startlingly clear leaded crystal glass - not a replication of the Venetian product after which it had been fashioned, but a distinct variety of glass entirely which had been fabricated almost by accident as a by-product of wider research. But was this the work of Ravenscroft alone, we await publication of some new research.
And so the point where English glassware could be easily discerned from European products had been reached, and the identifiable early features of our native pieces began to evolve. It was immediately apparent that, although bright, lustrous and clear, the lead glass was slow to cool and therefore difficult to fashion in to intricate shapes in the Venetian style and baluster glasses came very much to the fore. Simple, plain, functional, sturdy, uncomplicated for the most part - they seemed typically English from the very start with their lack of continental sophistication and frippery. Neither could the new glass be blown thinly to provide a suitably delicate and uniform base for engraving, so the development of decoration - as it gradually became more sought after - was by way of shaped knops and balusters to the stems, impressed prunts or crimping and pincering to the surface - pleasingly stolid and reassuringly phlegmatic adornments as befits the staple glassware of perfidious Albion on the cusp of the industrial revolution.