I strongly recommend reading this:
Edith Mannoni, Opalines, Paris 1974.
Having read an extract it gives an excellent explanation and history of French Opaline glass.
Paul,
Yes it does seem as though the term 'opaline' has been appropriated in more recent times (turn of the 1900s? from this book extract) but in my opinion for what it's worth, it is an appropriate description.
Anne,
I didnt understand that sorry. Does that mean that only translucent glass made in France from crystal can be described as opaline glass?
I think from reading the extract, that it becomes clear the development of opaline glass has progressed in stages/ages.
It cannot be fixed into 'only glass made with bone ash of certain decades and made in France by Baccarat'. That would not be true.
I don't even think it would be true to say it has to be hand blown and cannot be pressed. Opaline is not a description of a process imho, but is a description of a final glass item appearance, an item which is not transparent, not opaque and is translucent and has been coloured/made in the batch.
The different types of opaline could be categorised though if really required, probably by age and country of make descriptors. It just that, categorising them does not make them not opaline.
I think you just have to know your market and what you are buying.
m