James River Branch: Tools and Supplies

Supplies: Liquid Acid Soldering Flux

Many modelers—even some seasoned ones—object to my recommendation for soldering flux. Some claim one should never use any kind of flux under any circumstances. The problem is that flux serves a very specific, vital purpose: preventing the metals being soldered from oxidizing. Once a metal oxidizes, solder will not bond to it. So, not using flux invites a lot of failed soldering joints. Others will claim that only rosin paste should be used. Paste works, yes, but it leaves a greasy residue behind that can corrode metal, and it's difficult to fully clean it off.

Liquid acid flux really is the right stuff. "But it's acid," some will say. Yes, it is acid, but it's not something to avoid because it somehow eats away the metal, which is the picture they have in their heads. This isn't correct; the acid's job is to chemically reduce (eliminate) oxides as they form, thus keeping the metal clean, promoting a good strong soldering joint. Liquid flux readily gets into soldering joints in a way paste can't. Plus, liquid flux is water-based, so it cleans up easily and thoroughly using plain water. As a bonus, it also works on stainless steel, which is otherwise nearly impossible to solder.

Once you try using acid flux, you'll never go back to anything else. It makes solder flow like lightning; the tiniest solder joints form quickly and easily; and it works safely on all electronics—something many veterans warn us against. Don't listen to them. I've been using it for many years, and consequently I've never had a solder joint fail. Try liquid acid flux; it'll make a believer out of you, and it will vastly improve your soldering.

Warning: Liquid acid flux produces nasty fumes when it's heated; be sure to have plenty of ventilation when using it.

Just getting started? Acid flux can be tricky to find; most sources sell large bottles of it at equally large prices with even larger shipping fees because it's a hazardous material. It's used in tiny, tiny amounts, so a couple of ounces will last a long time. I order it from Micro-Mark because they sell a useful-sized bottle. (It comes with a sample of silver solder, which you can use—or not; it's the flux that's important.)

If you'll be doing a lot of soldering, you can get acid flux in 16 ounce bottles from a variety of vendors on eBay.