Thursday, February 27, 2014

What makes glass valuable?

The discovery that a simple mixture of sand (silica) and sodium carbonate could make glass is attributed to the Mesopotamians 5,000 years ago. We still depend on this formula today, exploring its versatility and beauty in countless ways.

Age is not an accurate barometer of value when assessing glass. A colourful 1950s Murano vase might be worth more than a 2nd century AD Roman glass phial. The assumption that a roughly made piece must be old, or that glass full of bubbles is an antique, isn't necessarily true either.

The art of making fine glass was mastered many centuries ago and it is such a versatile medium that over many millennia it has been fashioned into a diverse selection of articles. Differentiating between valuable pieces of 1930s Murano glass, an 1880 Bohemian overlay vase or a 1790s English Beilby enamelled drinking glass could make the difference between selling an items for a few hundred pounds or tens of thousands.

Over the centuries, the basic recipe for making glass has been refined. The addition of lime transformed humble water-soluble soda glass into the more durable soda-lime glass that accounts for most of our everyday glass objects. The use of potash and lead oxide were pioneered by leading glass-makers such as Englishman George Ravenscroft in the late 1600s. The term 'lead crystal' dates from this period. It denoted a higher quality glass with an enigmatic sparkle, prevalent in old glassware made for the table. people still refer to their best glass as 'crystal'.

It is worth looking to see if you have any 18th or 19th-century glasses lurking in the back of a cupboard. Often surviving as single entities, they sit unused for lack of matching companions or perhaps they simply don't hold much liquid. Ale glasses from the 18th century are a case in point; usually conical with perhaps a spiral or 'wrythen' body, their small measure is an historical testament to the strength of 18th-century brews. typical examples sell from around GBP 30-80, more for a less common design or one with an engraved pattern.

The art of cutting, engraving and polishing glass is another important aspect. Machine-made glass must never be discounted. Depression glass is popular in the United Stated; 19th-century British pressed glass manufacturers, such as Sowerby and John Derbyshire, are collected, although they are unpopular at the moment. There are even collectors of Pyrex, who can pay up to GBP 15 for a 1950s lemonade jug with six glasses.

The best place to sell art glass from any era and rare drinking glasses is at auction. Pieces from the 20th century will do best in a dedicated 20th-century design sale. Or try specialist dealers or sell online.

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