View Full Version : Solder identification

12-05-2011, 01:13 PM
Over the years, several coils of solder have accumulated in my toolbox. I know there are silver solder, plumbing solder, unfluxed electrical solder and who knows what other type in there.

Anyone have a way to determine which is which after the label/packaging is long gone?

12-05-2011, 01:53 PM
If you can measure the melting temperature and the range of temperatures during which the solder is in a plastic mode (not a liquid, but not fully solid either), you can take a pretty good guess at what is what.

Maybe a simple soldering iron run off a dimmer with a thermocouple on the tip. You could slowly raise the temperature and watch where it melts.

Silver solder woudl be obvious as opposed to lead-tin types of solder as the melting temperature is much higher.

The fluxes can be catagorised a bit by seeing what solvents will dissolve them easily. i.e. water, alchol, etc.

12-05-2011, 04:17 PM
Plumbing solder is always heavy gauge. I'm not sure it comes with an acid core flux, i'm pretty sure you have to add that.

Anything small gauge with a flux core is likely for electronics use(eutectic 63/37) and the flux will almost certainly be rosin.

12-05-2011, 05:35 PM
If it is true silver solder, not silver bearing solder is will be kind of gold colored and very stiff. Other than that you can pretty much interchange the solders. The only thing you really have to watch is acid core solder. That will mess up electronics and a lot of other things big time. You can take a sharp knife and cut the solder. If a liquid comes out it is acid, sometime a whiteish powder. If it is brown it is rosin core for electrical.

12-05-2011, 06:25 PM
Another way to till acid core from rosin is to melt some. When melted the acid core kind of spits and sputters rosin does not.

Your Old Dog
12-05-2011, 10:15 PM
I found out by using new can of flux with old style solder. It wouldn't work.

12-06-2011, 10:32 AM
Through dumb luck, the one I needed had the label still on the roll when I turned it over:rolleyes:

None of the unlabeled rolls have core, all solid. I bet they could be identified via chemistry... I know the compositions of the 3 or 4 things they could be. Must be some tests with certain chemicals which would allow one to rule out one or the other...

12-06-2011, 05:14 PM
If it''s "old" plumbing solder, odds are it's 50/50 or 40/60 tin/lead. Either one will have a noticeable mushy range, where it is neither really liquid or solid.

If it's 60/40, close to the eutectic, it will melt sharply and not have much of a mushy range.

Probably the easiest way is to measure melting temperature, as somebody suggested. 60/40 will melt slightly above 437F, if I remember correctly. (I think eutectic 63/47 is 437F.) 40/60 and 50-50 will be higher.