The ancient process of refining silver is being described. Lead was placed in a crucible with the sliver ore and exposed to intense heat. The lead would then become oxidized and would collect the impurities and leave the silver behind.1 Only in this case the process failed. The lead is consumed by the fire; in vain the refining goes on.
No silver is produced. Jeremiah has declared the Lord’s message passionately and diligently, but not even the fierce fire of the Lord’s word can bring about the refining of this people, for the wicked are not removed
.2
29 The bellows blow fiercely; the lead is consumed by the fire; in vain the refining goes on, for the wicked are not removed.