Slag Glass Lamp

Q: I’m looking to find some info on this slag glass lamp. It was my grandmother’s and is over 60 years old. Thank you.

A: The opaque bent panels of pressed glass with the creamy, golden swirls in your lamp are typically referred to as slag glass. We use this term only because it is a widely known, descriptive term for pressed opaque glass with swirls or streaks, even though the likelihood of it containing any slag is remote. True slag glass is richly marbleized, deeply colored glass rather than glass that is colored with pale swirls or streaks, which is also known as malachite, marbled and variegated glass. True slag glass was originally produced in England during the last quarter of the 19th century when, simply put, it is believed slag from iron-smelting was added to molten glass to achieve a marbling effect in a variety of colors. It was used to make all types of glassware, including panels for lamp shades. American companies (Taylor, Northwood, Dugan, Akro Agate, Westmorland) began manufacturing this type of glass during the late 19th to early 20th century. They also began producing opaque golden, creamy colored glass known as caramel slag that allowed the passage of enough light to give a room a soft, warm, golden ivory glow. True slag glass is richly marbled while a handsome example of pressed glass is simply colored or streaked. Your caramel slag glass paneled lamp dates from the 1910s through the 1920s. Your lamp appears to have six panels and looks to be in very good condition. The wiring is not original to the lamp; originally it would have had cloth covered wire. Rubber and vinyl coated wires were not used until the post-World War II era. It is a rather nice example of lamps of this type and would have a value of $300 to $400.