Not All Glass is Created Equal

Pressed glass, Depression glass and crystal - this month we'll review the basics of these different types of glass and some tips on telling the difference.

History

Glass was first recorded being made in ancient Rome, Egypt and Syria. It was made by heating and fusing sand, potash or soda with lime.

Types of Glass

Soda glass, potash glass and lead glass are the three main types of glass.

Soda glass

Starting in the 13th century, soda glass was made in Venice. Glassmakers were able to form molten glass into elaborate shapes because it contained burned seaweed, making the glass very malleable.

Potash glass

Potash glass came from northern Europe. Potash was made from a combination of burned wood and bracken making the glass well suited for engraving and cutting.

Lead glass (crystal, lead crystal)

Starting in Europe in the 17th century, lead glass was developed. It was derived from adding lead oxide to potash glass. The words lead glass, lead crystal and crystal all mean the same thing. Crystal is simply a type of glass. It is the addition of lead to mix that makes crystal harder than regular glass. Crystal is less likely to have bubbles, which is helpful when cutting

Pressed glass

Popularized during the Victoria era, pressed glass is made from a mould and is less valuable than cut glass. You can identify pressed glass from the mould line that is visible and the less sharply faceted decoration.

Depression glass

Popularized during the Great Depression, companies such as Hocking Glass, Federal and MacBeth-Evans mass-produced this form of pressed glassware. It was often given away free as a gift with purchase. There are many colours and patterns available.

Decoration on glass

There are four types of decorations used to adorn glass: cutting, enamelling, gilding and engraving.

Cutting

Facets cut into glass reflect light and create sparkle. One tip to help date a piece of glass is to look for shallow surface cuts which were used in the earliest days of glass cutting.

Enamelling

In the 15th century, the Venetians popularized the enamelling of glass that is a process of painting on glass.

Gilding

It is a technique of adding gold decoration to glass that was often done by firing the gold onto a glass surface.

Engraving

It was done by diamond point engraving (scratching the design onto the surface of the glass using a diamond nib), wheel engraving (scratching the design on the surface of the glass using small copper wheels rotating against the surface) stipple engraving (scratching the design onto the surface of the glass using fine diamond needle that taps out the design in a series of dots and lines) or acid etching (scratching the design on the surface of glass using a sharp tool then subjecting the glass to hydrofluoric acid which etched the design onto the glass).

How to tell crystal from cut glass

Weight is the number one tip-off that something is crystal rather than glass. The lead in crystal makes it is heavier than cut glass. The telltale ping when you flick your fingernail against crystal is another way to tell crystal from glass.

Why is modern-day crystal less brilliant than antique crystal

Crystal made in the early 1900s contains about 25 to 28 percent lead. Modern crystal contains only 10 to 12 percent lead. This reduction in the lead content makes modern crystal less brilliant than antique crystal.

How to tell if it is early glass

Old engraving will look dark and grey against a white background. New glass engraving will not look grey against a white background.

Spotting reproductions

There are many reproductions circulating because modern glassmakers made imitations of 18th century glass. There is nothing wrong with reproductions as long as you know that is what you are buying. You can spot reproductions three ways:

Colour

Reproductions may not have the distinctive tint caused by natural occurring impurities. Use the white background test; if the engraving looks grey against the white, the item is likely to be old.

Manufacturing signs

Machine-made glass will not have the rough bump under the stem that hand-blown glass will have. This bump results from the item being removed from the glassblower's rod. Also, hand-blown glass might have imperfections such as uneven thickness, ripples or striations that machine-made glass does not have.

Proportions

Styles and proportions have varied over the years. One thing to look for is that the foot on antique glass is often as wide as the bowl.

Value

Glass and crystal are one collectible where the secondary market is more affordable than the primary market. The reason is supply and demand. Plenty of crystal was made over the years, plenty of people took good care of it, and, as a result plenty of it is still around.

Martin Swinton owns Take-A-Boo Emporium, an antique shop located in Toronto, Canada. He does furniture restoration, caning and rushing repairs, custom reproductions, upholstery, teaches courses on antiques and does appraisals for estates and community events. He can be reached at 416-785-4555 or by visiting http://www.takeaboo.com