Mr. Boulais, You neglect to say what flux chemistry you are using, rosins, water solubles, low solids, etc. It may be possible to use a titration method to determine the amount of flux present. We attempted such a titration method in the IPC Phase 3 low solids flux project to determine the amount of low solids flux applied to the test boards. We had limited success, but the low solids flux was 95% isopropanol and the evaporation rate was high. Such a method might work on the more acidic RMAs and OA fluxes. Les Hymes, The Complete Connection, may be able to provide you more information. Doug Pauls [log in to unmask]