Vaseline/Uranium Glass
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Who Wants Radioactive Glass ? – I Do.
by
Barrie Skelcher ~
Author of "The Big Book of Vaseline Glass"
Mention the word radioactivity and most folk
will cringe, think of cancer and the atomic bomb. The fact
is that radioactivity has been with us since the world began
and that life has evolved in a radioactive environment. One
of the most used radioactive elements is potassium, it will
found in some garden fertilizers and even in the substitute
“low sodium salt” which now appears on some shop
shelves. It is potassium that makes the Dead Sea, arguably,
the most radioactive sea in the world. Another element that
is widely distributed throughout the Earth’s crust is
uranium, and that, as every schoolboy and
schoolgirl knows, is radioactive. For over a hundred years
it was used extensively in the glass industry.
Uranium was discovered by the German chemist
Martin Heinrich Klaproth, who reported his
findings in 1789. In fact he had not isolated the element
but its oxide. It was not until 1841 when the French Chemist
Eugene Peligot isolated the metal itself.
That did not stop the element being used to colour glass,
just when this first took place is uncertain. There is a contention
that it may have been used in Roman times, this hinges on
a piece of mosaic found while excavating a Roman Villa near
Naples. This is tenuous and is unsupported by other evidence.
Discounting this, various other pieces of evidence suggests
that it was sometime between 1800 and 1830.
In those days it must have been an expensive
commodity, a surviving Stourbridge batch book, dated 1860
–77, indicates that for a batch of “opaque yellow”
which contained about 0.7% uranium, the uranium would account
for about 60% of the total material cost. It is likely that
the discovery of uranium deposits in the USA in the 1880’s
brought cheaper supplies to the market and lead to the expansion
in the use of this element. It probably reached the peak of
its popularity in the first part of the 20 th century. After
WW2, despite the abundant availability of “depleted”
uranium, its use in the glass industry rapidly declined and
is now only used by a few glasshouses in specialist production.
This may be due to there being other means of producing similar
colours and at the same time ever greater health and safety
restrictions on its use. Not withstanding there are still
many examples of uranium coloured glass in use and waiting
to be discovered by a collector.
So why did uranium glass become so popular
a hundred or so years ago? There are probably two reasons.
The first concerns the range of colour that it could produce
in glass, and which could not be obtained by other means.
These range from turquoise to green to yellow to topaz to
amber within which there is almost a continuum gradually changing
shades. Perhaps the most popular of these amongst collectors
is what has become known as “vaseline”
glass. It is greenish yellow with a slightly oily appearance
and closely resembles the well known petroleum product. Unfortunately
some modern dealers now stretch this to quite unjustifiable
lengths. I have even seen items described as being “pink”
or “blue” vaseline glass. The second reason for
its popularity in those distant times is probably related
to the characteristic, ghostly green, fluorescence that it
shows under ultra-violet, (black) light.
I am not suggesting that the Victorians and Edwardians flooded
their rooms with this invisible light but rather that nature
did it for them. Although gas lighting was starting to make
an impact a lot of properties still relied upon oil and candles.
These would not be lit until the last moment when the twilight
finally gave way to darkness. As the sun sets the first colour
in the spectrum to go is red, the last is violet and with
it the neighbouring ultra-violet. Thus as darkness falls the
ultra-violet component of the spectrum predominates and uranium
bearing glass starts to glow. It must have been an attractive
sight in those homes of long ago.
Uranium gives a green or a yellow colour
according to the chemistry of the mix. Other colours found
in uranium glass are corruptions of those due to the presence
of other elements. The ever popular Queen’s Burmese
has an opacifier and gold in the mix. The former makes the
item translucent while the latter is responsible for the rich
rose red where the item has been reheated. The milky effect
on the edges of Davidson’s Primrose Pearline
is due to the presence of arsenic
There are two easy ways to detect the presence
of uranium, neither are absolutely fool proof. The most popular
is with ultra-violet light. It is now possible to buy, for
a few pounds, u-v light sources that are designed to detect
forged banknotes, some can be as small as the fob on a key
ring. The drawback with u-v light is that it can not be used
in strong sunlight. Also some other agents fluoresce much
the same as uranium. In recent times I have seen glass items
coated with such agents and to the inexperienced or unwary
they could be mistaken for uranium. Some glasses, especially
those which are heavily leaded and of dark amber colour only
respond weakly and could be overlooked.
The alternative is to use a Geiger
Counter. These are much more expensive and may well
cost over £100. If a Geiger is used it should have a
thin window and be suitable for measuring beta radiation.
A good test for the suitability of such an instrument is to
hold the detector against a bag of sulphate of potash, (fertilizer)
and see if a reading is registered. If it is, then the instrument
is sufficiently sensitive. Even the Geiger is not foolproof.
Some glasses with high potassium will give low readings. More
importantly some, which have been made with sand naturally
contaminated with thorium. This could occur when ceria has
been used , instead of uranium, to produce a yellow. If the
cerium had been obtained from monazite sands then it would
like to have thorium as an impurity. Thorium does not fluoresce
under u-v so a combination of the two tests is very reliable.
The advantage of the Geiger Counter is that it can give a
good approximate measurement of the uranium content of the
metal.
Finally if you ask is this glass dangerous,
the answer is may be, may be not. Read “the
Big Book of Vaseline Glass”, by Barrie
Skelcher, pub. Schiffer 2002, to find out more.
© Copyright Barrie Skelcher. 2004. ©
Copies of “The Big Book of Vaseline Glass” may
be obtained from most booksellers or direct from the author.
Email skelch@sumplace.abelgratis.com
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