If the Mods want this elsewhere, it can be moved to wherever is the best place. I'll reply later to Fred's request for Archive pix re the Sowerby pieces.
Believe we've discussed the matter of the misuse of the Sowerby trade name 'blanc de lait' before, but just thought it worth clarifying again, since the term has been wrongly associated - in the literature - with plain white vitro-porcelain.
The pieces shown by Roy are white vitro-porcelain, and hand-decorated with enameled colours, whereas blanc-de-lait was decorated with opaque staining, and is a true opalescent glass.
Lattimore (1979) uses the term 'blanc-de-lait' correctly and shows one of the swan decorated spill vases. Like Raymond Slack, he recites the well known story of the Newcastle tradesman returning from Paris with several pieces of this novelty opalescent glass only to be told it had originated in Gateshead, and as such he had been 'carrying coals to Newcastle'.
Lattimore adds the word 'opaline' to his description - which is probably incorrect - he may have meant to say opalescent.
He also shows some opaque white vitro-porcelain, decorated with enameled colours.
Sheilagh Murray (1982) uses the name when referring to hand painted plain white vitro-porcelain, although on the same page she shows a genuine piece of opaque coloured stained blanc-de-lait, and calls it 'early opal bowl hand painted in ochre'.
Simon Cottle (1986) follows Murray precisely in using the term to describe white vitro-porcelain decorated with enameled colours - but a little later in his catalogue shows stunning pieces of blanc-de-lait which he describes simply as "opalescent press-moulded glass with amber staining".
Finally, we get to Raymond Slack (1987) who describes correctly both blanc-de-lait and hand-enameled white vitro-porcelain.
The value of Slack's book is in the thoroughness of his research........... fortunately he provides factory evidence to
support separate descriptions leaving us in no doubt as to which is which.
Extracts from both Sowerby's own advertisements and the Pottery Gazette are quoted.
With hindsight, it was perhaps unfortunate that the factory chose to use the word 'opal' to describe their very first white vitro-porcelain.
sorry if this is all boring, but just thought it worth repeating to help avoid confusion.*