I wonder if it is possible to transport Star San in checked luggage for an intercontinental flight?
I plan to buy a couple of bottles in the US and fly back to Europe and I wonder if it's possible.
While inquiring with the FAA or other appropriate authorities is the only way to get a proper answer to that question, offhand my thought would be "No." Star San is a blend of phosphoric acid and dodecylbenzenesulfonic acid. Since acids are classified (under aviation and other regulations) as corrosive liquids I expect this would not be allowed.
Whether or not you can get away with it is of course another matter, but it's not a gamble I myself would want to take, especially not in the US.