Jamieson, Fausset and Brown on Jeremiah 6:29

29. bellows ... burned--So intense a heat is made that the very bellows are almost set on fire. Rosenmuller translates not so well from a Hebrew root, "pant" or "snort," referring to the sound of the bellows blown hard.

lead--employed to separate the baser metal from the silver, as quicksilver is now used. In other words, the utmost pains have been used to purify Israel in the furnace of affliction, but in vain (Jr 5:3; 1Pe 1:7).

consumed of the fire--In the Chetib, or Hebrew text, the "consumed" is supplied out of the previous "burned." Translating as Rosenmuller, "pant," this will be inadmissible; and the Keri (Hebrew Margin) division of the Hebrew words will have to be read, to get "is consumed of the fire." This is an argument for the translation, "are burned."

founder--the refiner.

wicked ... not plucked away--answering to the dross which has no good metal to be separated, the mass being all dross.