What is Mercury Glass?
Mercury glass, also known as silvered glass, contains neither mercury nor silver. It's actually clear glass, mold-blown into double-walled shapes and coated on the inside with a silvering formula, which is inserted though a small hole that is then sealed with a plug. A few manufacturers did, for a time, try to line their glass with a mercury solution; this practice was discontinued due to expense and toxicity, but it helps explain the origin of the misnomer.
First discovered in early-19th-century Germany, mercury glass was used as an inexpensive and tarnish-free substitute for silver in such objects as candlesticks and doorknobs. It then gained favor in France and England, where it was made into useful household wares like vases and goblets, and in America, where it was turned into glass vases, goblets, tankards, sugar basins, tumblers, and even spittoons. Some critics condemned it for "looking too much like mirror and too little like silver," which is precisely what people liked about it. At worst, mirror attracts a few vain glances, while genuine silver attracts thieves. Appreciation for the inexpensive baubles rose, until the advent of the lightbulb: in "modern" light, no burglar would mistake glass for silver.
Mercury Glass Revival
After briefly falling out of favor, mercury glass reappeared around 1900 in the form of pretty Christmas ornaments and gazing balls, as well as blown fruits and flowers. Today, most serious collectors concentrate on antique forms, like curtain pins, salt cellars, or pedestal-footed silvered vases. Many such vases were decorated by assembly lines of little girls, each of whom would paint her own specialty -- such as swans, leaves, or daisies.
Rose bowls, made primarily in the 20th century from colored mercury glass, are also sought after by collectors. Silvered-glass objects with acid-etched decoration, often of wheat or flowers, turn up frequently; cut silvered glass is much rarer. (You can tell the difference by rubbing a finger over the decoration. Cut glass has definite edges, while acid-etched glass will feel slightly rough.)
Buying and Caring for Mercury Glass
Mercury glass is still relatively inexpensive. A vase in perfect condition might cost between $80 and $100; painted pieces can sell for $200 or more; colored, engraved, cut, and labeled pieces can fetch more than $1,000. Exposure to air causes oxidation of the silvered inner surface and makes it flake off. To keep air from entering through the hole in a piece's bottom (where the silver-coating process begins), the original manufacturers developed several sealing methods, among them a cork covered with a wax plug, and a lead plug sealed beneath a disc of glass. Still, corks dry up and wax falls out, so some believe that more than half of the mercury glass available today is damaged. And serious collectors want their glass perfect (unless it is in some rare form). Some buyers, however, actually prefer pieces with a crumbly, deteriorating coating. Between the A-one and the "as is," there's plenty of glass for everyone.
As for care, John W. Keefe, curator of the large silvered-glass collection at the New Orleans Museum of Art, offers two important suggestions. First, he warns, don't remove any painted decorations. His second suggestion is a nice surprise: If your antique silvered glass has lost its seal and has begun to deteriorate, you can arrest the process by shaving a wine cork to fit the opening and corking it, or by covering the hole with a plug of malleable wax and allowing it to harden.
Do You Know?
Known as "poor man's silver" in England, mercury glass provided an inexpensive alternative to the silver that furnished the houses and churches of the wealthy.