BlackLight UV 4W Handheld; Make it Glow!! A1+

This Vaseline Glass Image is Copyright © 2003 Tony Hayter (1st.Glass)

This Vaseline Glass Image is Copyright © 2003 Tony Hayter (1st.Glass)

Uranium salts (Uranium Dioxide), as found in their natural state, are a vivid yellow. So it's easy to understand why it has been added to glass as a yellow colourant since the early 19th century. There have been claims that its first use was as early as 79 AD following the discovery in 1912 of a glass mosaic in an excavation on a Roman Villa near Naples in Italy but this has never been proven. Some others consider that its first use was by Josef Riedel at his Bohemian glassworks in the 1830's. There is no doubt though, that in 1835 experiments with uranium as a glass colorant were being carried out by Whitefriars Glass Works in London and that in 1836, a pair of uranium glass candlesticks were presented to the Queen. Production of uranium glass in Britain ceased by the end of the second world war but a small amount is still being manufactured in the USA and Czechoslovakia.

This Vaseline Glass Image is Copyright © 2003 Tony Hayter (1st.Glass)

One of the most significant aspects of uranium glass is that it is radioactive and does give a positive reading on a Geiger counter. We are reliably informed though that as the radioactivity is at a very low level it is quite safe. The other significant aspect is that it glows a vivid bright green under Ultra Violet light (blacklight). This is due to the Ultra Violet radiation exciting the outer electrons of the uranium atoms which as a result give off energy and is seen by our eyes as a bright green glow. This is called fluorescence. The more intense the UV the brighter the green glow and the less that the original yellow colouring can be seen. Uranium glass also has a slight green glow in daylight due to the Ultra Violet component of daylight acting on it. This glow is paler due to the effect of the other components of white light also striking our eyes.

'Vaseline Glass' is a term that has been adopted for a type of uranium glass which is transparent, has a yellow-green hue in daylight and fluoresces bright green under Ultra-Violet light (black light). So, strictly speaking, anything outside these parameters should just be called 'Uranium Glass'. To further confuse the issue, glass collectors in the UK have adopted the term 'Vaseline Glass' to describe opalescent glass. To avoid confusion I always refer to any glass with opalescence as 'opalescent glass'.

This Vaseline Glass Image is Copyright © 2003 Tony Hayter (1st.Glass)

Apart from Vaseline glass there are many other types of uranium bearing glass, some of which have also been given names. For example some opaque uranium glass tends to be called 'Custard Glass' and if it also has a pink tinged satin area to part of it (caused by gold in the mix being reheated), then it may well be termed 'Burmese Glass'.

This Vaseline Glass Image is Copyright © 2003 Tony Hayter (1st.Glass)

The higher the uranium dioxide content in the glass then naturally the greater the coloring effect is, which can exclude some transparent glass from the Vaseline glass definition because the yellow colour is so dominant. Other colourants were often added to glass in addition to the uranium dioxide. The colour yellow is formed by Red+Green, so when a green colourant is also added, green then becomes the dominant colour of the glass, yet it will still fluoresce bright green under Ultra Violet light (blacklight). Other combinations of colour are rarer but I have found shades of amber, blue, turquoise, pink, white and grey glass all with a positive uranium dioxide content (Confirmed by testing with a Geiger counter) and all fluoresced a brilliant green under Ultra Violet light (blacklight) except for uranium glass with a high lead content which exhibits a reduction in green glow due to the damping effect of the lead.