Powder Vs Paste Flux

Flux is a chemical compound, and is in most cases made in powder, liquid, slurry or paste. So what is the difference between powder fluxes and paste in terms of usability?

Powder fluxes are necessary for specialised applications in order for the flux to work properly when connecting a join. Particularly in a furnace brazing process.  Advantages are that they have a longer shelf life as powder doesn’t require water. It is cost effective as you should be able to convert it into paste by adding water or alcohol.

Using a paste for say silver brazing, provides excellent capillary flow and an extremely clean braze. Paste can be used for torch, induction, and furnace applications. In these applications flux is usually added to paste formulation. When using paste in a vacuum or atmosphere furnace flux does not need to be added to the paste.