| To the general public the word uranium
is synonymous with nuclear weapons, nuclear power stations and radioactivity.
But the term uranium glass, to the collector, will always be associated
with that oily, yellow-green, transparent medium known colloquially
as Vaseline glass. However, this is only part of the story. |
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| The chemistry textbooks tell us that uranium
was discovered by the German chemist, Martin Heinrich Klaproth, in
1789, which is perhaps a simplification of the truth. The element
was named after the planet Uranus and what Klaproth reported to the
Royal Prussian Academy of Science in that year was uranium oxide,
which he had separated from the heavy, black mineral known as pitchblende.
The element itself was not isolated until 1841, but this did not stop
it from being used in glassmaking. |
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The chemistry of uranium is somewhat
complex as it has several valency states. It is also amphoteric, being
able to act as either a base or an acid. Hence we can have such compounds
as uranium nitrate or sodium diuranate. This must have made life somewhat
bewildering for the early 19th century glassmakers, especially as
the chemists of those years had only a very crude understanding of
molecular compositions.
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PLATE 1:
Selection of late 19th and early 20th century wineglasses,
all coloured by uranium. |
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Perhaps this is why in the surviving batch books of those days we
find such loose terminology. For example in a Whitefriars batch book
of 1832, on the same page we see the terms “Saltpetre”
and “Nitre” used in adjacent recipes when they were in
fact the same compound, i.e. potassium nitrate. In other books we
see recipes using the term “lead”, “litharge”,
“red lead” and even “lead or litharge”. We
now understand that these are not the same compounds; while litharge
contains about 93% lead, red lead may only have as little as 90% of
the element. Much the same applies in the early recipes to uranium.
Sometimes the word is “uranium”; at other times it is
“uranium oxide”. Will they be referring to U3O8, which
predominates in pitchblende, UO3 that occurs in becquerelite, “uranium
yellow” which is an intermediate stage in the processing of
pitchblende and is sodium diuranate, or even orange uranium, which
is potassium diuranate? The percentage of the element uranium in these
will vary from as much as 85% to 64%. All this adds to the areas of
uncertainty as we unravel the use of uranium in glassmaking over the
past 150 years. |
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| But who first thought of using uranium
to colour glass? Some authors give the honour to Josef Riedel at his
glassworks in Bohemia in the 1830s. It may be that he was the first
to produce uranium coloured glass in quantity with his Annagrun and
Annagelb - green and yellow glasses named after his wife - but it
is unlikely that he was the first to add Klaproth’s discovery
to sand and alkali. We know from records held by the Museum of London
that Whitefriars used uranium colouring in 1836. There is good reason
to believe that the British scientist, William Vernon Harcourt, started
experimenting with glass compositions in 1834. He did not publish
his work but it would appear that by 1861 his work had included uranium.
There are reports of a uranium glass beaker cut with a portrait of
the famous German poet and dramatist Friedrich Schiller. He died in
1805 and it is thought this beaker commemorates the 20th anniversary
of his death, as it is inscribed with the date 1825. Between 1800
and 1809, Thomas Cock, brother-in-law of P.N. Johnson of Johnson Matthey,
working at the laboratory of William Allen at Plough Court in Lombard
Street, studied the extraction of uranium oxide and its application
to the colouring of glass. An early English reference to uranium in
glass also comes from C. S. Gilbert’s Historical Survey of Cornwall
(1817). He devotes sixty pages to Mineralogy and Mining and mentions
a number of elements used in glass manufacture. With regard to uranium
he states: “Its oxides impart bright colours to glass, which
are, according to the proportions, brown, apple green, or emerald
green”. From all this we conclude that the colouring properties
of uranium were known early in the 19th century, but it was not until
the second quarter of the century that it was marketed. |
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Notwithstanding the foregoing there are
suggestions that uranium was used by the Romans. The story revolves
around a find near Naples in 1912. A sample of a green Roman mosaic
was brought back to England and analysed at Oxford University. It
was reported to contain uranium. For a more detailed account, the
reader is referred to Caley’s Analysis of Ancient Glasses, 1790-1957,
A Comprehensive and Critical Survey, Corning Museum of Glass, Corning,
New York 1962. There are good reasons for suspecting the findings
of the Oxford scientists to be fallacious. For example, if uranium
oxide had been deliberately used by the Romans, from where would they
have obtained it? It is hardly likely that a budding Roman geologist,
after globe trotting round the world, clutching a bag of strange earth,
would have rushed up to the glassmaker as he was about to make the
melt for his tesserae and say “hey, try putting this in your
mix”.
If that did happen, why was it not repeated and how come the discovery
was lost for the next two millennia? Until the measurement is repeated,
I remain sceptical about this claim. |
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| My opinion is that it is unlikely that
any one person invented uranium glass. The most likely explanation
is that various scientists and glassmakers explored the use of uranium
in the early part of the 19th century, and that during the second
quarter of the century some items made from coloured uranium glass
were being produced for sale. |
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| It is difficult to know just how rapidly
the interest in uranium glass developed. From the samples I have studied,
most of which are subject to my own dating, I am of the opinion that
it did not gain popularity until the last quarter of the nineteenth
century and was then used by most glasshouses until the start of the
Second World War. However there is an interesting note in the Pottery
Gazette and Glass Trade Review (September 1891) which states that
“fifty years ago it (uranium) was first used in glass and we
think then it was new, or at all events a scarce mineral, and our
older readers will remember the rage ‘canary yellow’ had
at that period in hock glasses, toilet bottles, etc. Amongst the early
makers of this colour in glass were Hawkes and Bacchus & Green,
who priced it at 3s. 6d. per lb. It was then only made in transparent
glass; now we find it in semi-opaque and ivory body, but like everything
in fancy glass it has had its day and is seen no more”. This
latter comment is a little hard to accept as Davidson’s were
at that very time producing their popular Primrose Pearline. Perhaps
the writer was ignoring the cheaper press moulded products made for
the masses! Nevertheless, deducting the fifty years brings us back
to 1841, which is only a few years different from what the other sources
indicated. |
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| Text © Barrie Skelcher and The Journal of
the Glass Association 2001. |
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