And they definitely, describe in great detail in patent documents how to make their "secret sauce", right? No, wrong. Patents are often written in a way to give maximum protection and minimum information how to recreate the thing.
according to the law, the patent office has the job of rejecting patents that don't give enough information, and throughout the middle of the 20th century they seem to have done a reasonably good job of it. i've found reams of valuable information in patents from that time period, though not specifically about vacuum-sealing glassblowing
also, fusion (not online, but available in many university libraries) is the quarterly journal of the american scientific glassblowers society https://asgs-glass.org/fusion-journal-asgs/ and they also have had symposia which have published proceedings (not online)
and it's common for scientific papers from the period when this stuff was getting figured out to describe their apparatus in detail (rather than saying they purchased such-and-such a model from such-and-such a company), and those are online
