Abstract: The instant flux and paste containing same are for brazing aluminum material. The flux consists essentially of a particulate blend of aluminum fluoride, potassium fluoride, and cesium chloride, or rubidium chloride or a mixture of cesium chloride and rubidium chloride, the fluorides being complexed with each other or not complexed or being a mixture of the complexed and not complexed fluorides. Lithium fluoride, preferably complexed with the other fluorides, is an optional ingredient. The weight fraction of the total fluorides is between about 1/10 and about 9/10, and the A1F.sub.3 -KF weight ratio is between about 4:1 to about 0.4:1.