Vaseline glass – made by adding uranium oxide and named for the trademark petroleum jelly – is different things to different collectors.

Many purists say the only true vaseline glass is yellow or yellow-green glass that fluoresces to a glowing green under a black light. Others favor opalescent or "lemon pearline" glass, shaded from yellow to milky white. Pieces like this vase, which has almost no yellow tones, are often categorized as green vaseline glass or even just "green Depression glass."

The vase was $25 at an M street estate sale. It isn't marked, but it probably dates back to the 1930s or early '40s. Vaseline glass was first made in the mid-19th century, when European glassmakers began to use uranium for yellow and green glass. In the U.S., it was made until World War II, when the government took over all supplies of uranium for the war effort. New vaseline glass is being manufactured today.

Some glass sold as vaseline glass does not glow under a black light. Many collectors carry a small ultraviolet light to test before they buy. Small enough to fit into a jacket pocket or handbag, the lights cost around $25 to $50 each and can be found in shops that cater to stamp collectors. (Philatelists use UV lights to ascertain if a stamp has been "tagged" with fluorescent ink, a step used by the post office to facilitate electronic sorting.)

Shadow play

Another kind of light trick is used for lithophanes. From the Greek for "vision in stone," a lithophane is made by varying the thickness of a translucent material, often delicate porcelain, so that an image is formed when the piece is held up to light. (Paper watermarks use the same principal of light and shadow.)

Lithophanes were especially popular during the mid-1800s. Lamp shades were often composed of lithophane panels depicting beautiful women, cherubic children or bucolic scenes. Vintage shades with all panels intact can bring more than $2,000; individual panels sell for $200 and up.

This Japanese-made lithophane teacup (with a matching saucer, not shown) was $5 at a recent sale near downtown. The geisha figure is a common motif in Japanese lithophanes; rarer and more valuable are erotic images, sometimes found on the bottom of sake sets. Also look for lithophanes on German steins; images include nudes, animals and military and hunting motifs.

Waltrina Stovall is a Dallas free-lance writer whose column appears regularly.