the best way to get the solder off is heat unless it on a rib of a double and if it is someone did a sloppy job use a propane torch then wipe it off with a wet rag it its in blued metal it should slide right off but i magine you are working with a spot where a sight was soldered on the barrel and plan on using touch blue to cover the bare metal.it it a rib get it ro someone who knows what they are doing the way you keep it from getting where you dont want it i use soap stone in the bare metal when soldering sight on barrels it will not attach and is a quick clean up. now a isuue raised with the hot bath blue it will remove sight that are soft soldered almost every time that why most dobles are rust blued ih it its on blued metal use a wood scraper and it sshould come right off for you
