Much like the depression glass we discussed in a previous post, slag glass is often found in homes as a collection or a few treasured pieces, despite its slightly unappealing name.
Slag glass gets its name from one of the components in it. Early manufacturers of this type of glass would add the waste content of metal ores from iron-smelting works, or “slag,” to their molten glass to create swirls of color within it. These swirls gave the glass a marbled look, and people often refer to slag glass as “marble glass.” Some companies achieved a similar look by mixing two colors of molten glass. The end result is often called “mosaic glass.”
It is believed that slag glass got its start in England, which remained the main manufacturer of this type of glass in Europe. It caught on in the U.S. and was made by several companies, mainly located in Pennsylvania, including H. Northwood Glass Co., Challinor Taylor & Co. and Atterbury. Another company that came to be known for slag glass was Akro Agate, which made a name for itself in the early 20th century with its unique swirled marbles made by their patented process.
Slag glass has been around since the late 1800s and became very popular in the early part of the 1900s, during the arts and crafts period. One of the most common uses for this type of glass at that time was in lamps because the white or off-white swirls within the color allowed the light to shine through. Tiffany lamps made with leaded stained glass were in vogue, but many people could not afford them because they were expensive to make. Companies started using slag glass fit into metal frames to create similar-looking lamps but at a much lower cost, making them available to more people.
Rather than being blown, slag glass is pressed into the desired shape. In addition to lamps, it frequently appears in vases, bowls, figurines and candy dishes. Chunks of this unique glass are also often used as a decoration on outdoor patios and in gardens where the sunlight accents the swirled pattern. Purple is by far the most common color, and was one of the original colors created by Sowerby in England, but it can also be found in blue, pink, green, red and various shades of brown.
Slag glass is still manufactured today, and many people enjoy collecting it because of its beautiful colors and unique patterns.