Topic: Check Out This Antique Engraved Glass...Any Ideas Who?

[KevinH]

It turned bright green, though.

Which indicates it is made from a Soda Glass mix, as opposed to a high-lead content. Unfortunately, that does not help with placing it to a particular company or even a country.

[Frank]

Which indicates it is made from a Soda Glass mix, as opposed to a high-lead content. Unfortunately, that does not help with placing it to a particular company or even a country.

Actually it does a bit as the Bohemian glass of the period was not soda glass but lime glass, it was known as Bohemian White glass and was very hard and thus able to equal lead for use in engraving. The typical formula being:

Pulverized quartz            100 parts
Carbonate of potash    28 to 32 parts
Slacked lime            13 to 15 parts
Oxide of manganese    1 parts
Arsenic                    3 parts

Note also the use of readily available quartz instead of sand.

[KevinH]

Hmmm. I should have said "non-lead" instead of specifying "Soda glass".

[krsilber]

Lead glass can fluoresce green as well in longwave UV, in fact ABP (lead) glass that fluoresces "apple green" has long been held as an indicator that it is most likely of American origin.  In this case, though, I'm sure it's not lead anyway.  

A lot of Lobmeyr isn't marked, especially if was part of a set.

You could always send them a photo - they're quite helpful.

Bohemian White glass and was very hard and thus able to equal lead for use in engraving

Since lead glass is quite soft, I imagine there could have been differences in the blanks or engraving designs and techniques between Bohemian and lead glass - shallower cuts, for instance.  Hmmm, an interesting thing to compare.  I wonder if that's one reason brilliant cut glass never got made much in Bohemia around the turn of the 20th C, when it was so popular elsewhere.

[Frank]

Since lead glass is quite soft, I imagine there could have been differences in the blanks or engraving designs and techniques between Bohemian and lead glass - shallower cuts, for instance.  Hmmm, an interesting thing to compare.  I wonder if that's one reason brilliant cut glass never got made much in Bohemia around the turn of the 20th C, when it was so popular elsewhere.

Quite likely Kristi. Plus of course the Bohemians are almost the inventors of the finest engraving and the more adventurous spread out around the world teaching in other countries. I guess those that were left were to stuck in tradition. I do wonder when they switched to using lead crystal and soda glass. Soda Glass probably in the early 20th century and the they were starting to phase out Carbonate of potash by the end of the 19th. I presume they continue with crushed quartz rather than sand even today? One for the Czech glass scholars I guess. :sm:

[krsilber]

According to Baldwin's Moser Artistic Glass,  "From approximately 1850 to 1930, most Bohemian crystal produced was based on a formulation developed at Meyr's Neffe."

Formula given:
silicon dioxide (sand)   65%
potassium carbonate (potash)  21%
sodium carbonate (soda)  5.6%
calcium carbonate (lime/chalk)  8.5%
(plus decolorants and refiners)

I imagine the "sand" is a mistake, or at least a simplification, short for whatever ingredients they used at different factories and at different time for their silicon dioxide.

Where did you get your formula, Frank?  It hasn't any soda.  And what's this about phasing out potash at the end of the 19thC?  Why would that do that?

Incidentally, Baldwin attributes fluorescent properties to decolorants and refining agents, and suggests using LWUV plus SWUV can help ID different types of glass.

[KevinH]

Baldwin attributes fluorescent properties to decolorants and refining agents

That's why I should  have said "non-lead glass" rather than "soda glass" - but I switched back into old behaviour from a time when I had become used to talking about "soda-lime" versus "lead" glass. But I still do not understand all the intricacies of what elements cause which UV reaction - but that sort of thing has been discussed in several threads over the years.