How to Use Brazing Flux
As a general rule it is better to use too much flux than insufficient flux on a joint. Insufficient flux will give rise to oxidation and which may cause poor alloy flow whereas excess flux rarely causes a problem and prevents oxidation from the area surrounding the joint.
Brazing flux is available in powder, paste and liquid form. For best brazing results we recommend mixing the powder into a paste before application. Both joint surfaces need to be covered and the most convenient application method is by brushing.
Hot-rodding is a technique used to speed up manual brazing processes. It is not ideal brazing practice but does provide an alternative to using a flux coated brazing rod in situations where water cannot be introduced to the joint.
Hot-rodding is where a brazing rod is warmed with the torch flame and then dipped into the brazing flux powder. The warmth in the rod causes flux particles to agglomerate and stick to the end of the brazing rod. Flux can then be transferred to the joint opening and applied to it. The components can then be heated to brazing temperature. If necessary, further brazing flux can be transferred to the joint area in the same way during the heating process.
Most flux residues left on the parts post brazing are corrosive and need to be removed. The majority of silver brazing fluxes have residues which can be removed by soaking and or washing in warm water.
Medium and high temperature brazing fluxes have more glassy type residues require chemical means or more commonly removal using mechanical cleaning or blasting.