I'm looking at a picture/photo of a stainless steel revolver for sale that has the front sight resoldered back on. The Picture shows black discoloration or residue on the sight and barrel end. Is this something that can be removered by polishing fairly easy or possibly wipe off with acetone or a light acidic solution like metal prep or viniger? Im assuming it can.



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To be honest, IMHO the seam would have to be inspected under a magnifying glass to decide.

Done one way and with proper flux all you will be seeing is flux residue and it would clean off leaving undamaged material underneath.

Done another way, say with an improper flux that is too aggresive and a temp higher than necessary, I could see this seam being pitted or discolored under the flux. If it was, most likely the area could be blended back pretty good either by hand or with a rotary tool and some small wire wheels/cloth buffs depending on the existing finish.

Anyway, YMMV but I guess my answer would have to be "It depends...."

caustic, not acid .. try baking soda and water, followed by water