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Bristol Blue Glass - a Long and Proud History

Bristol blue glass has a long and proud history. This is a summary of how it came to be and the inspirational men who made blue glass what it is today.

Although it was once thought to be, Bristol blue glass is not unique to the city of Bristol. We now know that blue glass was made throughout England and even abroad and that the earliest known example of cobalt blue glass dates to as early as around 2000BC in ancient Mesopotamia. We also know that blue glass was made, fairly extensively at one time, throughout the British Isles but it is the blue glassware of Bristol that garners the most fame.

It is unknown exactly when glass production began in Bristol, although it is known that glass was being made in England during the 1500s. However, this far back, glass was produced with wood fires and occurred in forested areas. When a new law was introduced in 1611 designed to prevent the widespread deforestation that had begun to be a problem in England at this time, wood burning furnaces became prohibited and glassmakers were forced to move their wares to their nearest coal fields. At this time, many of the glassmakers from the Forest of Dean, just north of Bristol, moved to the large coal fields surrounding Bristol.

Whilst this was a necessary move for the glassmakers, it also brought with it many opportunities as Bristol had many important things to offer. First and foremost, Bristol had a large dock which allowed for both raw materials to be imported and for finished items to be exported. Indeed, as the industry of the area grew throughout the years, this proved to be imperative and during the early 1700s as many as four ships were departing each week, fully laden with finished items, destined for a variety of overseas destinations. It should be noted however, that this continuous trade, mainly with America, proved to be both a boon for the industry, but later its downfall. In addition to the benefits provided by the docks, other factors made Bristol a good location. Sand was dug locally and kelp was found nearby which was burnt to make potassium salts, both important ingredients involved in the glass making process.

With so much on offer, Bristol helped the glass industry as a whole to flourish and many types of glass were manufactured here. Initially founded in the widespread manufacture of windows and bottle glass, the glassmakers honed their skills and when the chemist George Ravenscroft discovered that adding lead to the mix produced a harder and more brilliant finish, these glassmakers widened their product base. This new type of glass was called lead crystal or flint glass and it was possible that it could be engraved to give a sharp image. Again, Bristol proved to be an ideal location for this process and lead was mined from the nearby Mendip hills. It would later be discovered that colour could be added which gave rise to the subsequent popularity of Bristol blue glass.

The glass trade was largely responsible for Bristol’s industrial success and whilst we know that it grew to quite some size during its peak and that it was highly sought after in wealthier circles, it is unknown exactly how popular cobalt blue glass was when the industry began to meet its demise in the 18th century. What we do know is that Bristol blue glassware of the time survives in much smaller quantities compared to clear glass and this is another testament to the fact that it was priced higher and was therefore only available to the wealthier clientele.

In the closing years of the 17th century, harsh taxation at a rate of 10% for windows glass and 20% on flint glass was introduced on the glass makers which temporarily thwarted the burgeoning market. This 10 year lull seemed not to hurt demand too severely though and when the tax was lifted almost 10 years later, the industry boomed. So much so, that a quarter of a century later in 1720, the writer Daniel Defoe claimed that Bristol was the greatest and richest port of Great Britain, seconded only by London. This is a considerable claim given that other ports, such as the many substantial ports in Liverpool, were both busy and active.

As trade demands grew and the industry flourished, there were more than 60 glass houses in Bristol, supplying more than 50% of Britain’s glass. The demands of the British colonies abroad tell only a small part of the story as there was significant demand coming from within the British Isles. Fine new houses were being built in the city of Bristol and in nearby bath that required glazing as well as fine dining wares for the wealthy individuals that owned them. At that time, the colour blue was associated with wealth and prosperity and as well as garnering interest from wealthy local buyers, it was adopted by the merchant venturers of Bristol as a status symbol. As the popularity of coloured glass grew, the first lines of cobalt blue hand-blown glass were introduced, and the name "Bristol Blue" was born.

Another period of harsh taxation stunted growth in the 1740s which meant glass makers had to choose from making either window glass or flint glass and inspectors were regularly sent to patrol factories ensuring that no one was producing flint glass but paying the lower rate of tax associated with window glass. While this did slow growth, it created an important divide in the industry that forced flint glass workers to move upmarket to produce higher quality goods. This also meant that relationships were forged with the skilled craftsmen that could engrave and decorate the glassware.

It is at this point that the real story of Bristol blue glass begins; one that is still celebrated today by the likes of Harvey’s who use only Bristol blue glass to bottle their famous sherry.

Richard Champion, a Bristol merchant and potter developed and patented a method for making pottery using the technology involved in glass making. Looking for a way to simulate the blue and white porcelain that had become sought after from the Far East, he approached the chemist William Cookworthy. Cookworthy was aware of a method using cobalt oxide, also known as ‘smalt’ which was being mined in Saxony. In 1753, he bought the exclusive rights to all the smalt in the region and began importing it to England over the next 20 years; exclusively to one port in Bristol. It was with this cobalt oxide that the flint glass makers of Bristol were able to easily and cheaply obtain the necessary ingredients to begin producing beautifully deep cobalt blue glass. While cobalt glass is by no means unique to Bristol, the fact that any other glass producer in England wanting to make blue glassware had to purchase the cobalt oxide from Cookworthy, added to the renown of the name ‘Bristol blue glass’.

Around the same time as Cookworthy’s import ventures boomed, a German man by the name of Lazarus Jacobs moved to Bristol and with his son, opened a workshop. They were fine craftsmen and very skilled at working with the newly developed flint glass and although the now highly fashionable cobalt blue glass was being produced all over the country, what set the Jacobs’ work apart from the rest was its high quality but also the fact that they were often signed – making them both easily identifiable but also extremely collectable. Over the years, the popularity of the family’s work grew and by the time Lazarus passed the business on to his son, Isaac, it was already a very successful venture. Isaac opened a new factory and grew the business, producing many sought after pieces of true Bristol blue glass. In fact, shortly after this he was recorded as describing himself as the ‘glass manufacturer of His Majesty’, although exactly what this means is unknown.

As time passed on, Isaac’s business grew and by the opening years of the 1800s, it is reported he was earning an astronomical £15,000 - £20,000 a year. With inflation taken into account this would be in excess of £1,000,000 today. Not bad for a glass maker! Sadly though, it was around this time that the glass market and Bristol’s industry began to dwindle. Taxation was prohibitively high for flint glass workers and coupled with the fact that many new glassworkers had begun operating in the newly liberated America, exports fell rapidly. To this day however, Jacobs’ glass continues to be highly collectable and extremely valuable, with many pieces shown in museums across the world, notably in the V&A museum in London.

This history laid a strong foundation for Bristol blue glass. Indeed, these individuals are the reason much of the cobalt blue glass that is found is often referred to as ‘Bristol blue’ but as mentioned, high taxation and lower levels of demand led to the eventual decline in the market and it wasn’t for almost 150 years later that cobalt blue glass was made in Bristol.

In 1988, expert southwest-based glassmakers Peter Sinclair and James Adlington joined forces and set up the Bristol Blue Glass company. At first they were unwilling to make the necessary alterations to the furnace in order to produce cobalt blue glass; adding cobalt oxide to the furnace meant that it was no longer able to produce clear or other coloured glass. It was some time before they took the decision to do so and after many small experiments with small quantities of cobalt oxide, they settled on a strong deep blue colour. They began at once creating and amassing large numbers of works from blue glass vases and glasses to other works in the style of vintage cobalt blue glassware which were sold through their gallery. When this had proved to be a successful venture, they took the decision to move to Bristol and found a pottery there which had all the necessary equipment needed for making blue glass. This was the true rebirth of Bristol blue glass and the first time this type of glass had been produced in Bristol on a large scale in nearly 150 years. To do this day, Bristol Blue Glass remain of the highest repute and are unrivalled in quality. They are widely regarded as the "original" blue glass manufacturers.

With the exception of a few improvements to available technology and conveniences, their method for making blue glassware and other coloured glassware for that matter, hasn’t changed much since the very early days more than 500 years ago.

To begin with, molten glass is held in a furnace which is essentially a bath of liquid glass. What makes this glass blue is the cobalt oxide, or smalt, inside the furnace. The compound that is added to the furnace does not physically add colour, rather, it alters the spectrum of light that is allowed to pass through it. This same method is used for producing different coloured glassware by adding different compounds to the furnace. Ruby glass, for example, uses gold – explaining its higher cost! This molten glass is gathered on to a hollow tube called a blowing iron and is then taken to a chair with an arm with which the glassworker can roll the tube and produce the necessary basic shape using a wooden block. A specialised metal tool colloquially referred to as a ‘jack’ is used to cut the neck of the glass piece. Air is then blown down the hollow pipe to inflate the ‘bubble’ of molten glass before it is once again rolled and scored with the jack. This process is repeated many times in order to gain the necessary shape and size – the bubble cannot simply be blown out to a large size in one go as it would likely become impossible to work with and or fall off and shatter. Throughout the process, the glass can be reheated in an extremely hot chamber, called a glory hole in order to keep it at a workable temperature until the finished shape is made and allowed to cool.

Whilst modern methods of producing glass may well be able to technically give more ‘perfect’ results, hand working glass using this method produces truly one of a kind glassware that is unique and of extremely high quality.