Topic: What is sodium glass and why is Moser glass different please

[flying free]

I've been querying a jug with enamel on it and Moser have very kindly had a look at the jug and come back and told me that the enamelling technique used was the type done on sodium glass and that is not glass they used.
In the interests of deciding a country at least for my jug, I wondered whether this might lead me away from Bohemia and towards France for example, or whether it is just down to different makers what they used and a time frame perhaps?
I'm not entirely sure what they meant to be honest and I'm not entirely sure what question I'm asking lol but help would be appreciated.
Many thanks
m

[Frank]

Bohemian glass was basically Silica, Silicate of Potash and lime. And was for a long time the 'whitest'European glass. Due to the lime it is harder than the soda glass used elsewhere hence it was good for cutting engraving. To reduce the cost the Potash could be replaced with sodium this would not be as white. 

[flying free]

Thanks 
just to clarify, because this is not something I've ever looked into,

did you mean that other countries used soda instead of potash in their recipes ? whereas if it were Bohemian glass it would have potash in and be much white than it seems my jug must be? 

Therefore I might be looking at France for the jug perhaps?

Also would this affect what kind of enamelling decoration was done on the glass do you know?
m

[Frank]

Typical Bohemian c1870s:

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

with some minor variations and mostly sourced locally. Though cheaper Soda was imported. Germany also used lime glass. Most everyone else used soda glass or lead of course.

It was ideal for most decoration, cutting, engraving, etching and enamel. Whereas in France and England soda glass was not so good for cutting and engraving, this gave Bohemia a cost advantage.

Never been able to find out when the switch from Lime to Lead and same soda-lime glass as most everyone else today really happened there.

[flying free]

wow thank you Frank. 

So, with this combined with the information from the specialist at Moser that the enamelling was that used on sodium glass, if my jug has enamelling on that is only used on sodium glass then I assume my jug is sodium glass and therefore unlikely to have been made in Bohemia.
I'd better start looking at France in a bit more detail then as well.
Thanks so very much
m

[Frank]

Not necessarily as it could be that he meant lime glass where soda had replaced the potash. Thus a decorator using a cheaper blank than their company. Ask him to clarify. 

[flying free]

Ok  I will send another email 
but I see what you mean.
I might try and look up some info on Harrach to see if they used both.
thanks again
m

[Frank]

It gets confusing as the use of lime spread from mid 19th century but the distinct soda and lime terms remain in the literature and mostly what we call soda glass today is actually soda-lime. One day I will have all the formulations in the study and can search and find things much easier than in my library.

And all Soda, Lime and Potash etc., can be shorthand for many variants chemically....