: Many thanks. I see the engraver Hauptmann is mentioned in the Atsushi Takeda paper, and is a name that Akiko and Sally had already picked up on. However, impurities in the sand, I believe, would not have been a reason to deter sheet glass manufacture. Adding certain chemicals would eliminate discolourations, such as greenish tinge from iron oxide impurities, but there is less emphasis on high-quality glass for use as windows, of course - I'm currently looking through my own windows, c.1916, which were almost certainly made using the much later Fourcault drawn-glass process - loads of imperfections here!
To expand on the early development of the glassworks, and referring to one of Akiko's papers (if I can find it online, I'll provide a link to the entire paper):
1873: Erasmus Gower - the first to be hired and responsible for building the first glasshouse. The pertinant point here is that the works is referred to as "the first Western-style glasshouse".
1874: Thomas Walton - installed the first furnace
1876: Government purchases the "financially troubled" plant after it fails to produce sheet glass the previous year, and this was using "experienced Japanese glassblowers". Plant renamed as Shinagawa after the locality.
1877: Elijah Skidmore arrives as a skilled potmaker (a very under-estimated and higly valued skill, IMHO)
- factory at this time is producing "daily products" and side-lights (navigational lights for ships). Sheet glass production is suspended.
So it can be seen that normal, low-cost glass is being produced.
1878: Walton leaves
1879: James Speed arrives as Chief of Craftsman. Akiko quotes here that, "Clay, various metallic oxides and moulds
imported from England." It is also noted elsewhere that Speed was probably the most respected of the engineers.
From this it is possibly pressed glass moulds that it refers to (the navigational lights could have been pressed, of course), but this is not certain.
1881: Sheet glass production resumed, but suspended due to "technical and financial difficulties".
Again, it is still unknown as to what the problems are exactly. 'Technical' is alluded to, but cannot be determined to the exact cause. At this time, "some 268 pieces of table-wares, scientific apparatus, chimneys and bottles are exhibited" at the 2nd inter-Japan Industry Promotion Fair.
1881: Skidmore leaves and takes up post in Osaka glassworks. Hauptmann arrives to take a position as an engraving instructor, but leaves after one year (finances again). Various engraving equipment is imported from England.
1883: Speed is dismissed and moves to Osaka.
1885: Shinagawa sold. It continues operating until 1892 "after adopting German manufacturing technique".Glen
: Thanks for your link! Akiko acknowledges that Japanese glassmaking was "technologically weak" until the arrival of the English workers, but it was still producing many items of glass. I'll contact you about the 'Lefton' label - I can provide a little more information on this.