[Formendacil]

I personally should consider it likely, if not certain, that the Dwarves introduced the Sindar to glass. After all, they also introduced them to chainmail, and seem to have been the first ones to make them swords (Telchar, a Dwarf of this era, is known to have been the maker of Narsil, which I think we can guess came to the House of Andunie via inheritance from the First Age).

However, it was not a one-way street. The Sindar and the Dwarves did a great deal of commerce in these early years, to their mutual profit (seeing the Silmarillion, the accounts of the building of Menegroth). Surely there would have been more than just an exchange of products. As the chainmail shows, there would also have been an exchange of ideas. It is entirely possible therefore, although not necessaily conclusive, that the Dwarves invented glass, or introduced it to the Sindar.