Crystal or Glass? How to Tell the Difference

The difference between crystal and glass is above all lead. Lead crystal is glass in which part of the lime has been replaced by lead oxide, at least 24 per cent in the EU, and this makes the glass heavier, clearer and more refractive, so that cut edges sparkle in the colours of the rainbow. Ordinary glass is lighter and often has a faint green tint at the edge. In everyday speech, however, fine, clear glass without lead is also called crystal.

Facts

The word crystal

The word crystal comes from rock crystal, the clear quartz, and has been used of fine, clear glass since the Renaissance. The glassblowers of Murano called their thin, almost colourless soda glass from the 15th century cristallo, and it was shaped into goblets with wings and loops such as the Venetian goblet. It was too brittle to be cut deeply.

In Bohemia a hard potash glass was made, with potash instead of soda, which withstood deep engraving, and it is often called Bohemian crystal although it contains no lead, like the engraved goblet. The modern meaning came from England, where George Ravenscroft patented lead glass in 1674. It was heavy, clear and strongly refractive, and his glass became the basis of English and Irish crystal. The terms are explained in the glossary.

What the lead does

Lead oxide makes the glass mass softer to shape and cut, heavier and more refractive. Light is refracted at cut edges as in a prism, which is why lead crystal sparkles in the colours of the spectrum. In the EU glass may be called lead crystal if it contains at least 24 per cent lead oxide and full lead crystal at 30 per cent or more. Glass with other additions, such as barium, zinc or potassium, may be called crystalline or crystal glass.

Many modern glasses for everyday use are called crystal but are lead-free. That is not wrong in everyday speech, but it is a different thing from lead crystal. Lead crystal should not be used to store wine or spirits for a long time, since lead can leach out, and it seldom tolerates a dishwasher without becoming dull.

How to recognise lead crystal

Weigh the glass in your hand: lead crystal feels clearly heavier than a glass of the same size in ordinary glass. Hold it to the light: lead crystal is very clear, without the green tint that ordinary soda glass can have at the edge, and the cutting sparkles in rainbow colours. Tap the rim of a stemmed glass gently: lead crystal often rings long and clear, but the ring also depends on the shape, so it is an uncertain test.

Look at the cutting. Deep, sharp diamond cuts and flutes, as on the decanter from Waterford, are typical of lead crystal, since the soft glass can be cut deeply. Pressed glass that imitates cutting has rounded edges and mould seams; see the guide to mouth-blown and pressed glass.

The history of crystal in glasses

English lead glass gave 18th-century drinking glasses their form: heavy wine glasses with baluster stems and then with air twists in the stem, like the wine glass with an air twist. Towards the end of the century glasses were cut in deep diamonds, and Waterford in Ireland was founded in 1783. In France Baccarat, founded in 1764, became the country’s foremost maker of crystal, and its millefiori paperweights are among the best-known objects.

Chandeliers were given prisms of cut glass that refracted the light of the candles, like the crystal chandelier. In Sweden Orrefors and Kosta became known for both engraved art glass and lead crystal, and Simon Gate’s engraved goblet shows Swedish engraving on clear glass.

Crystal in Sweden

Swedish crystal has a long history. In the second half of the 18th century Stockholm became known for its chandeliers, where chandelier makers such as Johan Lindegren and Lars Hallman worked with cut glass from Swedish glassworks. Kosta, founded in 1742, made chandeliers and tableware, and in the 20th century Orrefors and Kosta became known for both art glass and heavy, clear crystal.

Older lead glass, from before the middle of the 19th century, often has a faint grey or yellow tint and small irregularities, whereas later crystal is perfectly clear. That is a clue to age but no proof, since later glass too may have tints. Fine scratches in a ring under the foot are natural wear and show that the glass has been used; a completely untouched foot on a glass that is supposed to be old is suspicious.

Marks and pitfalls

Older crystal is seldom marked. Waterford glass from before 1851 mostly has no signature, whereas glass from the new factory after 1947 has an etched signature or a seahorse. Baccarat marked with an etched or embossed stamp, from the 1930s often a round stamp with a decanter and two glasses. Swedish glassworks engraved name, artist and model number; the guide to glass signatures shows how they are read.

Be careful with words such as crystal-clear or crystal glass in a description: they say nothing about lead. If the content matters, ask the maker or an expert. The guide to porcelain, faience and stoneware asks the same questions about material and manufacture, and the page on glass has the whole history from Murano to studio glass.

How to recognise it

Exercise

A glass is heavy, very clear and has deep cutting that sparkles in rainbow colours. What is it probably?