Silver solder? ....... or what?

I have acquired a bundle of what appears to be silver solder rods that I know came out of an elderly ( dead actually) toolmakers toolbox. Given the tarnishing I'd guess they had been in his toolbox for a long time.

I have my doubts though that these rods are bog standard silver solder but I'd like to know exactly what they were intended for.

They are all 3/32" diameter and 18" long. I have done a rough and ready melt test compared to a piece of known Easy-Flo N0.2. The Easy-Flo melts more readily than the mystery rod but the mystery rod melts with a nice silver glob just like silver solder should. The test was done using a standard chefs blowlamp filled with fag lighter gas.

Finally, each rod has been colour coded on the end with a dab of yellow paint and what to me seems very strange is that unlike Easi-Flo solder the ends of these rods shatter when struck with a hammer......very odd!

Any ideas?

Rik

I have some bronze welding rods for cast iron which display a similar traits and sort of splinter if bent at 90 degrees. I don't have the type as I bought them over 30 years ago but solder castings great.

David

You can use silver solder to join steel and other ferrous metals, unlike soft solder it makes a strong joint

If the rod melts close to Easy-flo temperature then it might be a Sil-phos alloy. Self fluxing on copper, but of limited use for other metals. AFAIK, Sil-phos tends to be brittle and the small amout I've purchased, a long time ago, was a rather dull colour.

Just a guess really!

You could take it to a jeweller who advertises they buy gold, in Birmingham they have a gun which tells them exactly whats in it.

Hi Rik

Considering your experience, I believe you have a silver solder.

The big clue to me is the yellow tip, only one that I know colour coded the tip of their rods. They only sold it in two sizes, 1/16 and 3/32 inch.

It identifies the probable supplier (and to me the manufacturer - UK) and also the alloy.

I would suggest that you are wasting your time involving a " jeweller who buys gold and silver". Why anyone would is beyond me - talk to a bullion dealer. You will get a much better price. Typically,a bullion dealer will give you 90% of the silver value less the cost of refining your package.

But I believe that you can use it successfully.

Regards

Keith

In my days when I was selling the stuff, would I have bought it from you? No.

Keith, is it likely to be a Cadmium bearing one in which case no one can now buy or sell it anyway.

But soulds like it will be OK for non critical home use if usual precautions taken.

The suggestion from Dave to take to a jeweler is a good one if, as I think Dave alludes to, they have an XRF analyser. This is a device, either desk top unit or a handheld gun that irradiates a metal sample with X-rays (or sometimes gamma rays) and measures the energy spectrum of the fluorescence given off. XRF stands for X-Ray Fluorescence. This is like shining UV light on something and seeing what colour it glows.
They are expensive machines but give very accurate non destructive anlalysis of the metallic content.

Robert 8RPI.

My guess is one of the several varieties of SIF bronze. Father in Law used to use it for repairing cracked Cast Iron with an oxy-acetylene torch . It's Silicon Bronze with a dash of of silver and tin in it There are lots of suppliers still around, . give one a call to check the colour coding.

Regards Bob D

"Considering your experience, I believe you have a silver solder."

Thanks Keith, was there a reason that you were reluctant to be more specific re: the manufacturer?

Clive Brown 1 - your info interesting and helpful, thank you. I did another test, and attempted to solder a small copper washer to a thin strip of copper. As you can see it worked a treat - no external flux was used.

Jewellers and bullion dealers not required - it stays in my toolbox!

Rik

Thanks for feed-back Rik. Due to it being an easily used, fluxless joining agent for copper, Sil-phos has, from time to time, been suggested for silver soldering boilers. However, I understand that it's not acceptable for this purpose as it's suffers from corrosion by sulphurous flue gases.

Can you not buy silver solder with cadmium in the UK ? Doesn't that cause problems when soldering boilers and pipework ?

NOTE : I am in Australia. Model engineer suppliers still sell silver solder with cadmium.

Not easily; available in the UK for industrial purposes only, which is pretty much the case everywhere in the world. I'm surprised Australia is more relaxed than other administrations, yet it seems so. Nonetheless, read what Safe Work Australia says about Cadmium, it's not safe. I hope Australians aren't using Cadmium-Silver solder in blissful ignorance!

I'm reminded of another wonderful manufacturing substance. It's non-toxic, fire-proof, and a first class sound, electrical and thermal insulator. It can be woven into cloth or rope, made into cement, sprayed, and made into superb brake blocks. Dirt cheap too. Though suspected early on, it took 50 years for the problem to cause enough trouble for it to be banned. Asbestos...

Dave

Robert, your father would not have used silicon bronze to oxy cast iron he would have used manganese bronze, very similar to look at but very different behaviour on cast iron.