Last Updated: Jul 19, 2016 Views: 82
You are correct in your thoughts that the ingredients for the composition of Lalique's opalescent glass is unknown. (The ingredients for his other types of glass are also unknown.) However, The Art of René Lalique by Patricia Bayer & Mark Waller (Seaucus, N.J. : Wellfleet Press, c1988) contains a brief section that describes Lalique's work with this material, including a formula that is considered typical. Based on this formula, it may be possible to speculate what Lalique's method may have been. We have attached this section as a scanned pdf that we hope will be useful.
For further information, as a good general introduction to Lalique's vast creative output, we recommend Lalique Glass by Nicholas M. Dawes (New York : Crown, c1986.). This is included in a bibliography of books in English about Lalique that is also attached.