Thanks for the source. It's not very sound and as I noted, very misleading. My comments on the quote from the book are in red:
...that prodution of carnival waned in the us in the mid 1920s (fair comment) and manufactures in europe, Scandinavia, and Argentina (and Australia, India, Mexico, Poland etc) began to produce their own carnival glass, to supply their home markets (the implied date is too late plus they also exported lots of it) and this was called secondary carnival (nobody calls it secondary carnival) was still hand pressed (or blow moulded) but with less finishing (not necessarily) and was made untill late 1930s (wrong on many levels).
In Britain, Sowerby's glassworks and George davidson (no no no to Davidson) reused 19th century pressed-glass moulds (only part of the big picture) to produce smaller ranges (smaller than what?) in marigold, blue (rare rare rare)and amethyst (and vaseline and black amethyst).