Slag glass, also known as marble glass or malachite, is a type of opaque, streaked pressed glass. Production of slag glass originated in late-19th-century England, where glass manufacturers are thought to have added slag from iron-smelting works to molten glass to create a range of effects—from tortoiseshell to marbling. Among other uses, slag glass was a popular material for lampshades.

One of the first glass foundries to produce slag glass (although it was not called that at the time) was the Gateshead, England, firm of Sowerby, which patented its recipe for purple malachite glass in 1878. Sold into the U.S. market as "blackberries and cream," this popular formula was followed by other malachite colors, including a lemon-yellow called Giallo, a drab green called Pomona, a blue malachite called Sorbini, and Sowerby’s famous Brown, which is very difficult to find today.

Since the process of making slag glass was shrouded in a certain amount of mystery, stories sprang up to try and account for the process behind the effects. For example, it was a good bet that Sowerby’s Blue Nugget color of 1883 was the result of adding cadmium to molten glass, but how to explain Gold Nugget? Stories soon spread that John George Sowerby, son of the company’s founder, was tossing gold sovereigns into batches of amber glass to create this dramatic hue.

In the United States, manufacturers such as Westmoreland and Akro Agate picked up on the techniques developed in England and produced their own versions of slag glass. As in England, one of the most popular applications for their pressed opaque glass was in lampshades. Wide bands of creamy colors allowed the light source in a lamp to fill a room with a soft ivory glow, while the purples and greens and reds pieced together in detailed leaded shades resulted in multi-colored illumination.

Just about anyone who was making lamps during the Art Nouveau period, from Tiffany to Roycroft to Steuben, might have used slag glass in their shades. But whether they did or not in a particular lamp is another matter. The problem is that today, "slag glass" is used rather casually by dealers and collectors alike to refer to almost any type of pressed opaque glass containing colored swirls or streaks. The key to determining if a piece of glass is "true" slag or just a handsome example of pressed glass is to look for glass that is obviously and richly marbled rather than simply colored or streaked.


Best of the Web (“Hall of Fame”)

The Lampworks

The Lampworks

Lamp collector and dealer Dan Edminster has put together an incredible reference site on antique lamps and related … [read review or visit site]

Texans Incorporated: The History of a Lamp Company

Texans Incorporated: The History of a Lamp Company

Mark Stevens has created an impressive living memorial to Texans Inc., a 20th century Texas manufacturer of ceramic… [read review or visit site]

The Lamps of H. G. McFaddin

The Lamps of H. G. McFaddin

Bruce Bleier's tribute to the Emeralite and Bellova lampshades made from Czech glass and popularized and distribute… [read review or visit site]

Fairy Lamp Club

Fairy Lamp Club

This incredible site is a stunning showcase for Victorian and contemporary fairy lamps, a style of lamp with a glas… [read review or visit site]

Gas Pressure Lanterns, Lamps and Stoves

Gas Pressure Lanterns, Lamps and Stoves

Terry Marsh’s beautiful showcase of gas-pressure lanterns, lamps, stoves, irons, and heaters from the 1920s o… [read review or visit site]



Clubs & Associations

Other Great Reference Sites

Most watched eBay auctions    

Huge Arts Crafts Handel,bradley Hubbard Wilkinson Slag Glasstable Lamp Shade NrExcellent Mission Oak Slag Glass Lamp Arts And Crafts Stickley EraAntique Arts & Crafts Table Lamp Slag Glass Mission Style Wb Brown Stickley EraVintage Slag 6 Panel Table Lamp By Royal Glass CompanyHandel Leaded Arts Crafts Slag Glass Antique Bradley Hubbard Era Lamp NrVintage Miller Lamp Base For Slag Glass Shade.marked M.l. Co 242 Antique Miller? Slag Glass Lamp Shade Intricate Art Nouveau Filagree WorkMission Arts Craft Stained Leaded Slag Glass Copper Sconce Lamp Stickley HandelAntique Three Light Stained & Slag Glass Lamp 21" Tall Lions Base Authentic !!!!Antique Vintage Art Deco 6 Panel Slag Glass Lamp Shade DamagedLarge Antique C.1920 8 Panel Bent Carmel Slag Glass Salem Brothers Lamp W/ H&h Vintage Antique Art Nouveau Slag Glass Lamp OrnateArts Crafts Stained Leaded Slag Glass Reverse Painted Lamp Base Tiffany HandelArt Nouveau Slag Lamp~great Colors~miller~slag Glass~curved~flowersFabulous Medieval Warrior King Figural Lamp W/ Slag Glass ShadeSigned Miller Slag Glass Boudoir LampAntique Slag Glass Banquet Lamp ShadeSlag Glass Shade Opalescent Tiffany LampBeautiful Antique Slag Glass Lamp Art Deco NouveauCirca 1890 Victorian Oil Lamp With Griffin & Angel Base W/ Slag Glass Lamp ShadeArt Deco Smoke Stand Floor Lamp Marble? Slag Glass Cigar Pipe TobaccoAntique Vintage Bridge Arm Table Lamp Slag Glass Shade Low Starting Low Reserve2 Antique Hubbell Double Pull Chain Sockets Fixture For Slag Glass Tiffany LampVintage Tiffany Style 16" Stained Slag Glass Lily Shade W/ 26" Table Desk LampVintage Torchiere Candelabra Slag Glass Floor Lamp Vintage Art Deco Antique Green Slag Glass LampHouze Glass Slag Bridge Lamp Smoking Stand Ash Tray Metal Stem Parts LotArts & Crafts Bronze Green Stained & Slag Glass Lamp ShadeVtg 16 Pc Slag Tulip Shape Swag Hanging Ceiling Fixture Glass Lamp LightMiller 1136 Old Vintage Metal Slag Leaded Glass Lamp Base Tiffany StyleVintage Tiffany Style Bevel Glass Hanging Lamp Dried Flower Leaf Clear Gray Slag Slag Glass Crown Ring 8 Panel Shade Crown For A Slag Glass Panel LampVtg Retro Deco "leaded Stained Slag Glass Geometric Lamp Shade", Assoc. Member**Vintage Retro Ceiling Light Fixture Lamp Stain Slag Glass Multi-color Original Vintage Leaded Slag Glass Hanging Light Fixture Swag Lamp Large Antique C.1920 8 Panel Bent Carmel Slag Glass Salem Brothers Lamp W/ H&h

Recent News: Slag Glass Lamps

Source: Google News

'Trashy Woman' Writes Book on Found Artists in South Jersey
The SandPaper, April 24th

It may have been an early influence, she said, with its miniature castle, huge flower basket and urn made out of bits of stone, Jersey glass slag, tiles, shells and cement. Her own 300-year-old farmhouse in Deptford is now part of Old Pine Farm, 40...Read more