thanks Carole - appreciate your link which is v. interesting, and deserves a good read - I only wish that I could find genuine late C19 States cut glass here in the U.K. I'm sure you know more about States cut glass than me, likely in view of your location - though there are some general pointers that apply to such material irrespective of origin. Have you posted this particular query on any of the States glass forums?
My only reference source for States cut glass is Jane Shadel Spillman's 'The American Cut Glass Industry - marvellous book, but it doesn't pretend to be a catalogue resume of all the patterns - don't know if you've looked in this book. Some of the ABP is to die for - especially the coloured pieces.
Saw-tooth rims are always at risk, and more so if they're over the century in age. Perhaps there's a misunderstanding of words re the green glow - I'm accustomed to seeing the word fluorescent only in connection with uranium, but maybe manganese 'green' has an equal right to the same definition. I think (and it's only a think
) that I know why uv light causes uranium to fluoresce, but technically I'm clueless as to why uv should likewise make manganese glow green)
The fluorescent glow form u. glass is far greater than the dull green I see from manganese.
What sort of base and internal wear does your bowl have - I appreciate there are those on the GMB who are a bit sniffy about the value of wear as an indicator of age, but generally such marks can be useful as to helping to indicate 'new or old', when viewed as part of the hallmarks of a piece of glass.
In the U.K., acid backstamps don't really appear on cut glass until after the first decade of the C20, and unlikely to be found on Victorian glass, and again, in the U.K., we see plenty of later C20 - and current pieces - of cut material with cutting similar to ABP, that are coming out of eastern Europe. Pinwheels, daisywheels and hobstars are seen commonly on Czechoslovakian material. It looks to be that Hoare and Hawkes were similarly using a backstamp as early as c. 1910.
As you will know, the provenance of States cut glass is nearly always twofold - one being the maker of the blank and the other the cutter, which possibly makes for a difficulty in knowing the whole story.
One of the general yardsticks of 'is it old or is it new' cut glass, is the appearance of the cutting - are the pattern edges sharp or smooth. The latter usually indicates a more modern production where the grinding marks have been removed quickly by the use of acid, as compared to the pre 1930/40 method of removal by polishing on wheels. Compared to early cutting, modern pieces are ruined by the acid, which takes away so much of the character and feel of the pattern.
Wish you luck with a decision on this piece - hopefully someone will have the answer for you.
Adding decolourizers to glass always baffled me, lacking as I do any formal chemistry education, so for those who may not understand why such additives are included in the batch - and why they should make dirty green glass white and clear - here is a little information that might help - courtesy of Wiki:-
""By adding certain other ingredients to a molten glass, it is possible to offset the greenish color and produce colorless glasses. Such ingredients are known as decolorizers, and one of the most common is manganese dioxide (MnO2). In chemical terms, the manganese acts as an oxidizing agent and converts the iron from its reduced state (which is a strong greenish blue colorant) to an oxidized state (which has a yellowish, but much less intense, color). In the course of the chemical reaction, the manganese goes into a chemically reduced state which is virtually colorless.
Manganese dioxide is believed to have been first used as a decolorizer as early as about the second century B.C. It was probably introduced as the mineral pyrolusite. From Roman times onward, glasses often contain about 0.5% to 1.0% manganese oxide (MnO). Later on, manganese dioxide (MnO2) was sometimes called "glassmakers' soap."
If pieces of decolorized glass containing reduced manganese are exposed to ultraviolet light for long periods of time, the manganese may become photo-oxidized. This converts the manganese back into an oxidized form, which, even in rather low concentrations, imparts a pink or purplish color to glass. The ultraviolet rays of the sun can promote this process over a matter of a few years or decades, thus accounting for the color of desert glass. The effect has been reproduced in the laboratory.""
I believe celenium is also sometimes used as a decolourant, and as mentioned above, we know some folk deliberately expose their pressed glass to the rays of the sun to create a sun-purpled effect, which apparently fetches more money - the assumption being that it will be older than non-sunpurpled glass.
Topic: ABP or European Cut Glass Bowl (Read 1207 times)
