Vaseline glass is a yellowish-green glass that contains uranium oxide thus when put under an ultra-violet or black light, will flouresce (glow) which makes it highly collectible. Imagine a room filled with this type of glass glowing or in a china cabinet with a black light in the top what a great artistic effect! Not all green or yellow glass is vaseline, however as shown in the pictures below. Sometimes frosted, satin or custard glass will flouresce as well. This is why a black light is useful and it can also be a useful tool for detecting repairs made to porcelain pieces. As an antique dealer this helps me quite often when purchasing glassware for resale. I find that a small hand held lamp is more convenient.

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Vaseline canoe under black light, and regular lighting.

Both appear to be plain green glass however...

under ultra-violet only uranium will glow the other bottle is plain glass and only reflects the violet in the bulb.

Here is an example of custard or satin glass.

Vaseline glass is fascinating and is a fun collectible but not always easily detectable, a small UV lamp can be easily found, are reasonably priced and well worth having should you choose this collectible. Happy hunting!