The Kester 331 organic flux is a water soluble formula for use in flux-cored solder wire. This cored solder version of the popular 2331-ZX neutral organic water soluble liquid flux is more effective than rosin fluxes in soldering difficult metals. The same fast action and mild properties are exhibited with 331 organic flux as with the liquid 2331-ZX. - The flux is more heat stable than most organic fluxes, resulting in minimal smoke and odor. The residue can be completely removed with a simple heated water rinse. Deionized water is suggested to prevent introduction of chemistries from unknown water sources. 331 is classified as ORH1 per J-STD-004.