Solder Flux is a liquid that is defined as a chemical used in the metal joining process (such as soldering, brazing, or welding) that is meant to prevent oxidation. Â For example, two common alloy used in soldering are Tin and Lead. Â Tin and Lead are commonly referred by their two letter abbreviations on the Periodic Table of Elements; Tin being SN and Lead being PB. Â (They are also seen as Sn and Pb). Â This Tin and Lead combination attaches or "solders" to copper excellently, but poorly to the oxides of copper, which are created during the high temperature needed during soldering.
Solder Flux saves the day by acting as a cleaning agent to remove the oxidation.
Kester Solder manufacturers solder flux in various forms, such as: Â flux pens (contains 10ml), one gallon containers, five gallon containers, 53 gallon drums, and flux inside of solder wire.
There five primary types of solder flux, based on their residue:
        No-Clean* | Kester 985M | Kester 959T | Kester 979VT
        Acid | Kester 2331-ZX
        Rosin** | RMA Kester 186 | RMA Kester 2235
        Water-Soluble*** | Kester 2331-ZX
        Solid | Kester 952-S
* Does not require cleaning after soldering
** Contain RA: Rosin Activated or RMA: Rosin Mildly Activated: Also do not require cleaning after soldering
*** Can be cleaned with water
Solder Flux Thinner is used to reduce the solids in the flux or to replace the evaporated solvent. Â As of January 2016, Kester offers 11 different types of Flux Thinner:
    100, 4125, 2164, 104, 108, 108S, 109, 110, 120, 4169, 4662