If you find factory cast bars that have no content marking, squeeze a known bar and the unknown bar together with a ball bearing between them. The softer (less tin content) solder bar will have a larger indent. There is no reason to pass up an unmarked bar that might be solder if you can buy it for the price of lead.
When I get unmarked solder or older rolls of solder that I can't read the label on I melt it all together, flux and stir it well, pour it into ingots and send a sample off for analysis. The last batch that I did ended up 51% tin and 49% lead. I leave any bar solder that is marked in its original form. I have bars of 60-40, 50-50 and 40-60.
Lightman I think has a good plan there. I have a few bars of solder picked out of the lead bin and find that the molded surface has been hammered flat. That prevents any possible ID as to source or type of solder. I have always suspected it left the work site in a boot or otherwise concealed. The comparison hardness test at least helps sort it out from other marked items. For wire solder, pour a small ingot and press test with a known sample.
Where do you send it and how large of a sample do they need?Originally Posted by lightman
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Member BNE is our great testing resource, but he's taking a bit of a break at the moment. That'll just give you more time to gather solder.
What he requests is a BB sized test sample and a pound of lead (I think he prefers pure). Your only other cost is postage. He'll flatten the sample, scrape a clean spot and XRF it. You'll get an email with the result.
Rotometals will do it, but the cost is one or two orders of magnitude higher.
Last edited by kevin c; 05-24-2020 at 03:12 AM.
It's pretty safe to assume if you get several random unmarked bars of solder & blend them the resulting ingots will be about 50/50 or at least close enough for our needs.
I take old roll solder and over hang the edge of my work bench equal distances about an inch and match it with known solder. I then hang fishing weights from them, the softer solder like 30/70 takes less weight to bend while 60/40 takes more & lead free solder takes the most. I can tell a lead free solder like 95/5. I get a lot of roll solder 95/5 has been the standard for 30 years here, 50/50 was standard before that silver bearing solder is rare. STERLING Lead-Free Solder is newer with 95%-96% tin/4-5% copper and trace of selenium. The core solders are the ones that can really run wild anywhere from 30/70 to 60/40 except the new lead free electrical solders which are mostly tin with trace amounts of copper & silver.
Another way to figure out roll solder by weight is to compare a measured length (1") of solder by weight in grains.
Kevin beat me to it but we have a member here, BNE, that has access to testing equipment. And like Kevin said, he needs a little sample between BB and Pea size to test. He ask for a pound of lead in trade per test. Thats a great deal for the members here! He's a great guy to work with and the forum is lucky to have him.
A recent post says he has temporarily quit doing this. You can contact him by PM.
This is true but I usually send BNE more than one sample to test so it only cost me another pound of lead to know.
The last batch of solder that I melted was a full 5 gallon bucket of mixed rolls of solder, some of them old enough to be on metal spools, and was about half full of water. Talk about a nasty mess!
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