Kutter, there are three that I find at HD made by Oatey, each a little different. This one is described as tinning flux. Is this the one you use? There are two others in Red and white plastic jars, one called No. 5, and the other H20 5.

https://www.homedepot.com/p/OATEY-8-oz-Lead-Free-Water-Soluble-Solder-Tinning-Flux-30142/100127686


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