An effective way to say "Do not use" on a bad spool of solder.
Solder doesn't go bad, the flux core goes bad. But something tells me this person uses more than the recommended Pauls of flux.
The cheapest solder out of China comes bad out of the package, and it's not because the flux dried out. It's because they use zinc-contaminated lead to make the solder in the first place. I played the China-solder lottery when I needed just a wee wee bit of superthin solderwire. Out of 2 different brands, one was fine, so I won that time. The other didn't need marking. It just went into the garbage can.
Once there's zinc in the lead, it is very difficult/costly to remove. It increases the melting temp and makes the alloy more chunky.
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The average casual user would probably never notice. As long as the flux is aggressive enough, it will flow just fine. I will notice immediately, because I do production soldering at specific temps. The bad roll melted at 20+C higher than normal. And it displayed one of the other characteristics of zinc contamination; the surface of the solderwire "fogs over" when it gets close to melting temp. You might also notice that even if you set your iron well higher, the wire still melts noticeably slower. As if it requires more energy to phase change from solid to liquid.
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This stuff sells on Amazon. If you notice, it's mostly 5 star ratings. Most people who buy shady solder won't know the difference, and maybe wouldn't care even if they did. But you also see a bunch of 1 star reviews complaining of dull joints, high temps, bad flow. So I have little doubt as to the reasons behind this picture. That was done by someone for whom the quality of solder makes a difference.