To the collector, perhaps the most popular
form of uranium glass is the Primrose Pearline produced by Davidson
at the end of the nineteenth century (Plate 4). For a time it became
a major prop in their business.
 |
PLATE 4:
Primrose Pearline cream jugs by Greener (left) and Davidson
(right), late 19th century. The Greener jug has the design
registry no. 262018 for 16th September 1895. The glass
is nearly identical
in both density and uranium content. |
|
The melt not only contains uranium but also arsenic. The latter caused
the glass to turn milky/opaque when re-heated at the furnace. Although
they held a patent, there is evidence that other manufacturers copied
the process. I have examined sixty examples of Davidson’s Pearline
glass; the average density is 2.53 g/cc with a range of 2.49 to 2.57
g/cc. This represents a variation of only 3%. It is interesting to
compare this with their clear glass of about the same period, which
is lower by about 0.06g/cc with much the same range. I can only speculate
that the presence of the uranium has caused this small difference.
Unusually I find a wide variation of uranium concentration, varying
from 0.22% to 1.36% by wt. This is far more than would occur by random
or even poor batch control. Moreover, in terms of colour intensity,
items range from a pale to a deep primrose. I observe that the palest
items have a uranium content of between 0.22% - 0.28% by wt. There
then follows a jump to 0.5%, which ranges up to 1.36% uranium by wt.
I can only speculate on the reason for this. Perhaps both pale and
deep colour products were sold over the same period, but with the
uranium content of the deep primrose being reduced to give a cheaper
alternative. |
| |
| Davidson also produced this yellow in
transparent colour. I have examined examples that probably date between
1910-1920. Their uranium content is about 0.74% by wt and they have
an average density of 2.49 g/cc. Unlike other glasshouses, Davidson
appears not to have used uranium in other colours. A large number
of greens, including all those on display at the Davidson’s
Glass Exhibition at Shipley Art Gallery in 1993, have been examined.
Only two items were found which contained significant amounts of uranium,
i.e. 0.03% by wt & 0.11% by wt. They are a grapefruit dish and
a piano insulator. Neither of these was marked but they were identified
from catalogues dating between 1928 and 1940. It is difficult to see
why, having not used uranium in the bulk of their greens, they should
use it for just a few items. Perhaps these were not produced by Davidson
but by some other glasshouse from Davidson moulds. We do know that
the Nazeing Glassworks did acquire some Davidson moulds and that Nazeing
also used uranium after the Second World War. Again, it is a matter
for speculation. |
| |
| The other major glasshouses on Tyneside
also used uranium extensively. Greener appears to have made an equivalent
of Davidson’s Pearline, despite the patent. Examples are few
and far between, but I have examined one item with the Design Registration
Number 262018 (Plate 4). This identifies it as being from Henry Greener
& Co., 1895. With a density of 2.53 g/cc and a uranium content
of 0.62% by wt. it is indistinguishable from Davidson’s Primrose
Pearline. |
| |
| Greener, and later their successor Jobling,
used uranium for other colours. Two of the original Greener notebooks
are in the possession of Sunderland Museum and Art Gallery. These
suggest that up to the 1880s uranium may only have been used for the
production of green glass but this is by no means certain. The colours
Topaz, Canary, Gold Yellow and Primrose, made by using uranium, are
mentioned after 1885. However I have found three Greener items in
yellow, with Design Registrations between 1867 and 1870. Their densities
range from 2.56 g/cc to 2.64 g/cc and the uranium content from 0.19%
to 0.26% by wt. It is quite possible that these items were made after
1885 from earlier moulds. Unfortunately I have not yet come across
a uranium green of the 1860/80 period. |
| |
 |
PLATE 5:
Glass by Jobling of Sunderland from the 1930s: jade green
bowl
(left) and green fir cone plate (right). |
|
By the 1930s, now trading as Jobling, the company used uranium in
their green and jade non-Pyrex glass (Plate 5), but I have not found
any yellow examples. Baker & Crowe in A Collectors Guide to Jobling
1930s Decorative Glass give a formula for the Jade which I would expect
to lead to a glass of about 2.60 g/cc density and 0.28% uranium by
wt. This is consistent with the few measurements that I have made
on their Jade. However the Jobling clear and frosted green appears
to have a lower density of about 2.47 g/cc and a uranium content of
0.13% by wt. |
| |
Sowerby, like their Tyneside competitors,
also used uranium. During the latter part of the 19th century they
appear to have used it in both green and yellow glass, but the only
examples from the 1930s I have found are green. With regard to their
1880’s wares, the yellows have a uranium content of between
0.25% and 0.5% by wt. I have examined only two
 |
PLATE 6:
Pressed glass by Sowerby of Gateshead, late 19th century:
dolphin bowl in
giallo vitro-porcelain (left)
and Queen’s Ivory bowl (right). |
|
green items and, although one was much deeper than the other, they
had a uranium content of about 0.37% and 0.43% by wt. respectively.
Perhaps the most interesting is their “Queens Ivory” range
(Plate 6). Sowerby patented their mix, which had 24 lbs of “uranium”
in 14 cwt of batch. Allowing for uncertainty about what is meant by
“uranium”, this is consistent with the measurements I
have made. Nine samples lie between
0.93% and 1.24% uranium by wt., but two other pieces have only about
0.65% uranium by wt. It is difficult to explain these variations unless
Sowerby found they could reduce the uranium without prejudice to the
colour, which in any case appears to vary in shade. I have also examined
one item, which is much more yellow that of the usual Queens Ivory,
which I take to be their “giallo” (Plate 6). Strangely,
its uranium content is 1.1% by wt., which is in the middle of the
range I find in Queens Ivory. It would seem that the deeper colour
is not obtained by higher uranium levels. Unusually for Sowerby glass,
the density of this glass is 3.20 g/cc (compare 2.52 g/cc for Queens
Ivory), which suggests it is loaded with lead or, more likely, barium. |
| |
The Lancashire glasshouses were probably
using uranium before the large Tyneside producers. A surviving pattern
book from the Manchester firm Molineaux Webb & Co suggests that
that the company was producing pressed glass at least by 1851. I have
examined six pressed candlesticks,
 |
PLATE 7:
The pressed candlesticks closely resemble items in the
Molineaux
Webb pattern book and almost
certainly come from that glasshouse.
The knife rests are probably also Molineaux Webb as their
density
is very similar to other Molineaux
Webb items. |
|
which are illustrated therein (Plate 7). They are all yellow bordering
on amber and their uranium content lies between 0.43% and 0.56% by
wt. Their densities are 3.3-3.4 g/cc, which probably means a lead
content (or possibly barium) of 35% or greater. Other, non-uranium
glass from this company, which I have examined, suggests that in the
1860-1880 period the density of their glass was about 2.8-2.9 g/cc.
I think it likely that lead content was reduced over the years to
keep production costs competitive, in which case the higher leads
represent the earlier glass. Almost certainly these candlesticks are
not typical of the bulk of Molineaux Webb glass. I have only been
able to examine a few items of uranium glass, which I consider, probably
originated from this glasshouse in the 1860-1900 period. One is a
pale yellow candlestick with a density of 2.68 g/cc and uranium of
0.26% by wt. The others are four green knife rests, all of the same
pattern (Plate 7); their densities range from 2.73-2.96 g/cc and uranium
from 0.25% to 0.37% by wt. |
| |
| |
 |
Page 3 |
|
|
| << Previous Page |
1 |
2 |
3 |
4 |
Next Page >> |
| |
| |
| Text © Barrie Skelcher and The Journal of
the Glass Association 2001. |
|
| |
