Abstract: A flux filtration system (10) for removing rosin flux from a heat transfer liquid (14). The flux and heat transfer liquid (14) on an article (17) that has been condensation soldered is drained into a pan (13) located within a condensation soldering facility (11). The pan (13) diverts the liquid-flux mixture from a boiling reservoir of the liquid (14) in the lower portion of the facility (11). The liquid-flux mixture drained during a plurality of batch soldering operations is accumulated in a coarse flux filter (21). Periodically the filter (21) outpulses the coarsely filtered material sequentially through a heat exchanger (23), a fine flux filter (24), a preheater (28) and is then returned to the reservoir in the facility (11).