Topic: Crystal Glass 1660s - Martin Clifford Thomas Paulden patent

[flying free]

Just curious about the difference between:
1)  a patent for 'crystal glass' given on 10th November 1661 Patent number 134 to Martin Clifford and Thomas Paulden
2) and a patent number 140 for 'crystal glass and looking-glass plates' given to Thomas Tilson on 19th October 1662,
3) and then the Patent number 176 of 16th May 1674 (thirteen years later) given to George Ravenscroft  for 'Manufacture of crystalline glass, resembling rock crystal':

See page 323 of this google books link -

https://books.google.co.uk/books?id=iArKCvphWicC&pg=PA325&dq=frederick+hale+thompson+George+Foord&hl=en&sa=X&ved=0ahUKEwijy6emlpveAhXmKsAKHVB8D3cQ6AEIJzAA#v=onepage&q=Pellatt&f=false

Was George Ravenscroft's Patent for a different type of crystal glass?  Were the earlier patents for 'making crystal glass' for making crystal or something else.  Or was George Ravenscroft's 'crystalline' glass resembling rock crystal not the same as their crystal glass?

I am aware of some of the info that is available online from Glass of the Alchemists but I don't have the book.
Was that patent for Ravenscroft in 1674 for making lead crystal?
If not then what is the difference between his crystal and the crystal of the earlier patentees?  Was their crystal the one that fell to bits because it didn't have lead in it?

m

[flying free]

oh ok, more info found on this link to the book:

'Inventing the Industrial Revolution: The English Patent System, 1660-1800

Pages 24 -27 which explains things a bit more -

https://books.google.co.uk/books?id=936BqhvTGSQC&pg=PA25&dq=crystal+glass+martin+clifford&hl=en&sa=X&ved=0ahUKEwi59IqPoZveAhVKAcAKHWA3Bd4Q6AEIJzAA#v=onepage&q=crystal%20glass%20martin%20clifford&f=false