Following from the EMPF HelpLine, prepared by Pat Kane: In my limited experience with spray fluxing, the biggest advantage seems to be the lower amount of material used during run cycles. The working life of the flux is greatly reduced in foam fluxing due to moisture absorbtion. This is not seen with spray since the flux is maintained in the container until sprayed. Cleaning of the spray machine is a tradeoff with the foamers, they both need to be cleaned well after each use to insure maximum performance. An added bonus to spray also seems to be less dripping of flux into the preheat area of the wave solder due to reduced material volume being used. This is not to say that the coverage results are inadequate. As far as quality issues, the proper setup of the spray should result in acceptable results. The hole penetration of the flux will be a setup parameter that will be of the greatest concern. Hope this helps.