It was just after midnight on a Thursday when the production supervisor called me. The new waterborne acrylic enamel line was foaming so badly that the finished paint looked like it had been whipped in a blender. Draw-downs were full of pinholes, and the spray booth was rejecting panels at a rate we hadn’t seen in years. We had already tried increasing the defoamer dosage from the original 0.2 % to 0.5 %, but the foam only got worse. That night forced us to stop treating defoamer selection as a simple “add a bit more” decision.