Since the dawn of time, human beings have figured out ways to use light, from fire in the dark, to crude oil lamps made from clay. Most antique oil lamps have an absorbent wick and are made from glass. There were antique oil lanterns as well, which were hand-held, and used in transport outside and throughout interior homes and barns.
Is your oil lamp primitive? Is it made from unpainted clay, or glazed terracotta? Unpainted clay oil lamps were used in Egypt, terracotta in Italy. In America and Europe candles were used, until pitch oil lamps were introduced in the 18th century.
In the 19th century, kerosene lamps came into existence, and Victorian era lamps were utilitarian, some made from hand-blown glass. Is your antique oil lamp hand-blown? Look for an indentation on bottom of glass or an inconspicuous spot. That would indicate a hand-blown piece where the stem of the tool used to blow the glass was broken off from the lamp when complete. Look at the burner. On earlier whale oil lamps there is one oil burner; on larger later lamps, there are two burners.
In the 20th century, slag glass oil lamps and other types were introduced, and became more decorative as opposed to purely utilitarian. Is your antique slag glass oil lamp hand-made or manufactured? Look for makers' marks on the shade itself to see if the piece is hand-painted, indicating an older antique oil lamp.
The shade is the focal point of an antique oil lamp. What does yours look like? Is it decorative? Check to see if it is made from slag glass, which looks like individual glass slates on an angle, sometimes separated by a line of silver resembling silver paint. Is the glass on the shade etched? Etched antique oil lamps are more valuable because they were hand-made.
Milk glass was an inexpensive creamy white glass regularly used to make antique oil lamps. If you have a milk glass antique oil lamp, hold the glass up to a light to see if it is translucent. Colorful art glass shades are more valuable and collectible today than plain milk glass. Look for cranberry, mother of pearl, satin glass and hobnail. There are two-toned milk glass oil lamps as well. If your antique oil lamp does not have a shade, the chimney, or the long part without the shade, will determine value. On antique oil lamps, the value may be retained without the original shade if the glass is rare, etched, colorful and intact with original parts.