Interesting article. They are hard solder brazing with a 40/30/20 Ag/Cu/Zn alloy using a fluoride flux (like SMAW flux) and a teeny tiny narrow window of heat where it actually might work, and oh yeah, don't forget to use a reducing flame. The entire article says how difficult it is, and that this may work sometimes for certain things. Inert gas furnace brazing is probably best for little sensitive parts, but this process would be impossible with tubing or work of any size that isn't engulfed in the flame. Unless it's a very small part, TIG with lots of argon purge is the best join.