The thing about using meths or surgical spirit is that the solvent burns as soon as a flame is applied and has the effect of making the flux adhere rather than running off as it does with water.
Rolls Royce aircraft engine specifications used to recommend the use of a drop of washing up liquid and this can be helpful but only a tiny drop is needed. They also recommended surgical spirit so as not to contaminate the joint with meths but meths works perfectly well.
Brian
Edited By Brian Hutchings on 20/08/2017 22:45:40