Originally Posted by
Doug Fattic
...boiling water removes brass flux a lot faster than tap hot water.
I do remember seeing an old hand steamer being used with Soap and Water to steam off Flux. It may have actually been Bronze Flux because they were cleaning joints on Bronze Statues they were assembling. When I questioned the crew they replied that any residual flux would migrate and destroy the statues patina over a period of years.
After washing with soap and water they would steam the joints aggressively and then rub in a paste of Baking Sada (bicarbonate of soda) then wash again with clean water.