Pair of Vaseline Yellow shaped Bowls, H:3.5" Diameter of top: 3 3/4". A history of Vaseline Glass was that primarily was made before WWII and one of the primary ingredients used to make the glass was uranium. When placed under a black light (or ultraviolet rays), vaseline glass will "glow" or fluoresce. The high energy emissions of electrons from the black light cause the uranium oxide particles in the vaseline glass to become unstable thereby causing this fluorescense. No other transparent antique glass will glow thus making vaseline glass truly unique in the antique world as it can always be verified to be true vaseline by using a black light. There is no other compound added to glass which will cause this effect except URANIUM. The yellow-green glow is characteristic of uranium-bearing glass. However, as glassmakers of the 1920's - 30's added iron to their uranium oxide dyes to put a green tint into their glass and although these pieces will flouresce under a black light also.It was thought that in WW11 the production of vaseline glass stopped and only in later years after there was a limited supply of uranium to glass companies in order to resume production of vaseline glass and even more recent pieces of vaseline glass are highly sought after by collectors as each is of a very limited production. LifestyleAntiques.com is the web site where one can shop on line or if you are in the area we are an antique dealer in Summerland, California just 3 minutes south of Santa Barbara. Specializing in European Antique Furniture and our accent is antique lighting for your home, or office with handmade parchment shades adorning the selection of unique lamps. We specialize in Decorative Arts and French furniture as well as antique furniture from Spain and Italy, you will find the shop warm and inviting.