Silver solder

Originally Posted by AuburnEwaste

In with some other junk I picked up today I found a couple boxes of lead free solder. Does anyone know if there is a market for this stuff? Most of it is scrap, but there are some un-opened canisters, though they are expired. I have about 55lbs of it.

It is 96.5% Tin, 3% Silver, and .05% Copper. I did some math and it comes out to just over 24 troy ounces of Silver.

I am glad to see that you figured for troy ounces, and did so correctly.

Please keep these things in mind when thinking about how much real value you have in the silver, and what you can get for it. It's worth, about, at today's sport prices around $385.00 - $386.00. A refiner has to factor in the cost of processing this type of material, and for myself I try to make at least 30% profit on anything I process to cover my time/labor and to make a small, reasonable profit so I can continue my work.

Solder with Silver alloys are not nearly as easy to process as other types of silver alloys. Tin creates a problem, if not processed correctly. Tin Oxide is very difficult to filter, so material like this is usually melted, and then processed in a Balbach-Thum or Moebius electrolytic cell, which requires melting the material into a bar or bars, and then processing in a vat filled with an acid solution. This requires energy (gas and oxygen) to melt the material, which also incurs a melt loss of a small percentage of the metal being melted. Because the material is considered "dirty", being that the Ag (silver) content is so low, a second refining is required to obtain high purity.

I am all for recycling any type of alloys that have values worth recovering, but often I pass on material just simply because the person selling it asks too much, and rarely wishes to negotiate a price where everyone can make a reasonable profit. Just shipping 55 lbs takes a nice big bite out of the profit. I don't have a problem at all with people who try to make as much off the material they work so hard to obtain, but too often there is no consideration as to how the refiner will recover their investment and make a small profit.

I would store the solder for now, and wait until you have a larger quantity to sell. In that way, you can cut down on some of the overhead making the material more valuable. If for example you were to find a silver solder alloy that was much higher in silver content, it allows the material to be processed if done all together, one time in a silver cell to be of high enough purity that it will not require a second refining. Also, when "dirty" silver is processed in a electrolytic cell, the solution is dirty, and must be processed also so that the "dirty" solution can then be replaced with a solution of only silver nitrate so that the cell can then be used again. This can be expensive as it adds an entirely different process to refining that otherwise could have been avoided.

Scott

Auburn, If the solder has flux in it and it's dried up then the solder would not flow correctly. When I first started out repairing radios I was using someone's left over solder from years earlier and kept having trouble with the solder joints "looking good". I asked an experienced tech and we talked about what I was using. Well he informed me that the rosin flux had dried up and not working properly.

After switching over to a new tube of solder then the problems with the bad solder joints disappeared. Most solders have either a rosin core or acid core. The acid core solder is some nasty stuff. As far as I know all solders have some kind of flux added.
That's all I got...

As usual Noble is dead on. My .02

Originally Posted by AuburnEwaste

I guess I did not point out that this is solder paste, not solid. Not sure if that makes a difference.

Then that would be for plumbers as they use paste and if needed then a flux before the solder. Radiator shops don't deal with as many copper rad's as they used to so there's not much use there.

Originally Posted by Abuilder

So much for the plumbing solder idea. LOL
High speed circuit printing yes.

Formulated for both standard and fine pitch stencil printi
ng, at print speeds of between 25mm/sec (1”/sec) and
200mm/sec (8”/sec), with stencil thickness’ of 0.004”
(0.10mm) to 0.006” (0.15mm). Blade pressures should be
0.16-0.34 kg/cm of blade (0.9 -2Ibs/inch), depending upo
n the print speed. The higher the print speed employed
the higher the blade pressure that is required

Kester 70-3213-0810 NXG1 No-Clean Solder Paste for Lead-Free Applications, 500 gram Jar

The paste flux system allows joint appearances that closely resemble that achieved with SnPb alloys

Longest shelf life at 8 months

Looks to be a flux used with a metal brush and not solder at all. And according to the info after 8 months the efficiency starts going downhill.

Interesting, I am actually formulating a silver solder for jewelers using organic binders that burn off completely at different temperatures depending on the formulation. Jewelers use solders that melt at different temperatures. In this way they are able to first solder a ring together with hard solder that melts at high temp. Then solder a bezel cup onto the ring using a softer medium solder that melts at a lower temp. This way when soldering a bezel onto a ring the solder that holds the ring together does not melt, because the medium solder melts before the hard. Depending on what the binders are in your flux, it might make it more simple, or more difficult to recover the silver. Also depending on the temp the solder melts may make a difference.

What color is the flux, is it white, or a pale yellow? When silver is alloyed with other metals, it sometimes will turn a yellow hue as it ages, this is why silver jewelry is often plated with Rhodium, and why people take their silver jewelry to be rhodium plated at a jeweler from time to time. Where the solder joints exist, the joints will start to turn a yellow color, or sometimes a pinkish color over time.

If you do decide to sell the flux, please do not to a large refiner. Even if they do take it, they are not tooled up to refine this type of material. Their melt loss will be far greater than someone able to process it properly, and will give you only a minimal return.

An interesting problem to say the least.

As a side note, I will be adding to by profile at some point. I now make custom jewelery out of some of the metals I recover and refine. I have been making alloys for jewelers, some unique like silver/palladium alloys. The metals jewelers use have small amounts of impurities specially in karat gold and sterling silver. I refine to high purity, and only alloy with metals I have personally refined so my impurities are brought drastically down to .001 of the total. When I refine jewelry I retain the stones and re-use them in the jewelery I design and make. For expensive stones I have them GIA certified. The concept is to take recycled metals and stones, and turn them into something special all the way from one end of the process to the other. This isn't a sales pitch, at least not yet. If interested or curious I will be adding to my profile as I said, with pictures etc. This will not be for a few months yet, as I am already swamped with requests, and I want to put up a website prior to actually offering this service.

Scott

Originally Posted by Abuilder

Are you kidding? Waste all those chemicals and time for a lousy %3 silver.
That silver solder is safe for plumbing contractor use and sells for $26 a pound!!!!!!!

If the refiner knows his work, and processes the material properly, there is no waste, when you use acids or other expendables processing metals, it's never a waste if done correctly because you have figured all those costs, and recover as much as you can.

Old solder is almost always useless unless, and this is the only cause, it's only metal. But often there is a core of flux, or in this case it's actually flux itself. Under those circumstances, the flux tends to go bad, becomes gooey and leaks out in some cases where it is warm, or it becomes hard inside the solder because the moisture evaporated, and will no longer burn off at the correct temperate because it's turned into a kind of cement.

If you can sell the unused solder paste/flux to someone who can use it, your suggestion is wonderful. However, I have processed enough solder to know that by the time it gets to me, there is no using it for any serious important work. Plumbing is serious, important work. Bad flux could cause a major leak, and water damage which the plumber will be responsible for, ultimately it will be their insurance. Plumbers charge a lot because they go through a lot of material like this, and that they have to carry hefty insurance in case something does go terribly wrong. Imagine how upset a plumber might be if you sold him bad solder, and it caused his customer damage, and his insurance to go through the ceiling or a dink against his license, a call to the BBB, etc.

Scott