Fascinating stuff. Thanks for the flag. I am guessing that the reason these techniques have eluded modern scientists is that the craftsmen of those times applied substances that were potentially dangerous to their health. They took risks that today’s scientists know to avoid.
As a side note: The writer of this piece is sorely lacking in writing skills.
I seem to recall something about the first metalsmiths who sculpted with platinum metals (there are four, generally found together in nature) had to dope it with something poisonous (arsenic I think) to keep it malleable long enough to sculpt.