This is the DCC Concepts Sapphire No-Clean Flux 50ml [DCS-SFNC].

DCC Concepts Sapphire No-Clean flux is an ideal companion that will make it possible for you to make perfect joints easily every time in electronics, soldering wires to track, working on or re-working brass, white metal or nickel silver kits… In fact anywhere that later clean might be difficult to do! The ONLY time you may want to clean this flux off post-soldering is if you wish to paint the area you have soldered, in that case, a simple wipe over with cloth or cotton bud dipped in Isopropyl alcohol or even methylated spirits is all that is needed.