Silver Soldering

1972Ren

The Comeback Kid
Hi all.
I have never used silver solder, and am wondering for what applications the different solders are used.
I see there are rods of 1%, 2%, 5% and some other contents right up to 50%
I gather ss can be used variously for joining a range of metals including copper, steel, stainless steel, silver, gold, cast iron, but I haven't been able to determine which different rods match up with joining different metals.

The chart on pp 34/35 of the document on this link (those are the original document page numbers, not of the pdf)

essentially implies that almost all the rods that company sells, can be used to join all metals! Which is interesting, but gives no indication as to why you would use one rod instead of another.

Question:
What difference silver solder rods have members here used and for what purposes?

Thanks
 

schlitzaugen

1000+ Posts
I have not had too much success with silver soldering but then again I haven't pursued it. I did need to silver solder some hard steel and it worked but what a chore. I guess I don't have the right equipment, mainly a powerful source of heat. I think short of oxy, you should use propane because it burns hotter. The different wires you see are definitely going to need different temperatures to melt so perhaps choose the wire after you choose the source of heat. I had no idea about any of that so I just went into my local shop and asked what they recommend. Can't remember what it was. They also sold me the flux. Which by the way, is important to make sure it's applied thoroughly and flows well into the weld. Don't know anything else.
 

jaahn

1000+ Posts
Hi Ando :)
I have done some silver soldering in the past. The different alloys are to give different melting temperatures, but there are no identification of the rods so you have to get some system for your self. I still have some rods somewhere.;)
The important thing is to clean the surfaces and remove any rust, oxide etc first. Use the correct flux which does not clean up the surface but just allows the solder to wet the surface properly. And you do need to get the temperature up with a good hot flame, and oxy is best. I am not sure of the flame setting now neutral, oxidising or reducing ?? The more silver the lower the melting point but the more expensive it is. Your choice.
I could dig out some information if you like. It is quite a while since I have done it. :rolleyes: But with copper and brass it wets and runs easily if clean but steel has to be used with a correct flame to prevent oxidising or burning. I preferred brazing for steel or cast iron. It gives a strong joint. Read that book and you will know as much as moi ! But any soldering is defined by close joints and capilliary action to draw in the liquid to fill the joint of the metals that do not melt. Brazing or bronze welding does not melt the parent metals but can add the filler on to the joint to build up the thickness of the joint. Silver solder does not do that much so the joint should be prepared appropriately.
Jaahn
PS I could dig out the rods and you could have them. PM me !
 

bob

1000+ Posts
also.... you can't use silver solder on something that has been "contaminated" with "normal" solders...
Bob
 

Attachments

  • SMEX - Silver Soldering.pdf
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  • soldering notes.pdf
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  • Temps.pdf
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JoBo

1000+ Posts
Jaahn and Bob covered it (y) Silver solder sticks do have an identification colour tip but it gets rubbed off over time. I think a Plummer told me many years ago that a 2% one makes stronger joints on copper pipes?
Anyway, i installed all my hydronic about 40 years ago and it is still good (no leaks ever). I used 2% and no Y or T connectors. Cut the pipe open and just stick another one in to branch off. One also gets a little scoop effect as the water runs in the main pipe past the branch. I hired an oxy set because it's way quicker and less heat spread under wooden beams/floor.
These days when i do smaller jobs i use MAP which works quite well but does take quite a bit longer and more heat spread - obviously.
BBQ gas is pretty crap doing silver soldering unless you go 15% or better but it's doable with less %ones.
 

PeterT

1000+ Posts
I silver solder a lot. My favourite is 45% silver, as the melting point is relatively low, around 650 from memory. I use this for everything. Lesser amounts of silver increase the strength and the MP. This makes it more difficult to use, as there is not a lot of difference between the MP and oxidised metal. Thus the higher risk of contanmination.


Since they outlawed cadmium, it doesn’t flow nearly as well. Luckily I still have some old sticks for special jobs. For other work, I’ve been using the orange coated flux sticks. I still prep with a paste flux however.

The key points are:
- perfect preparation with abrasive paper
- neutral flame, low
- never point the flame where you want the solder to run. Let the heat travel slowly. Be patient.
- when the paste goes glassy, it’s almost at MP
- wash in water and thoroughly remove any traces of flux (wire brush or abrasive paper), otherwise it will corrode
 
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PeterT

1000+ Posts
The other important point about low MP silver solder is that it can be used to join dissimilar metals. eg brass to stainless steel, should you desire.
 

shibuichi

Member
Avoid getting solder rods confused by grabbing a pair of flat nose pliers and putting 90 degree bends in one end of the rod.
One bend for easy
Two bends for medium
Three bends for hard
Added bonus during stick feeding the join is knowing the bent end of the rod is not the hot end.

I’m more familiar with precious metal than plumbing applications so I don’t know about the tin/antimony/lead solders referred to above. Using silver/copper/zinc solders the work can be overheated and burn out the zinc resulting in poor solder flow. It’s a Goldilocks zone of getting the work hot enough without being too hot. Keep the torch moving to get the surrounding area up to temp and then guide the heat along the seam. The solder will try to flow to the hotter area but won’t flow at all if it’s too hot or you keep the flame on too long.

And always use hard solder first. Save medium and easy for any necessary reworking. That said, the melting temperature rises as the zinc burns out of the solder so you can potentially rework with the same grade solder.
 
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shibuichi

Member
Re: torches

I decided I didn’t want an oxy tank taking up space in the workshop so I opted for an orca torch with pol adapter for a standard swap n go bbq bottle.
https://www.jewellerssupplies.com.a...h-kit/category/187-solder-torches-accessories

To get heat control where I wanted I have been known to go double torch combining orca with a disposable propane similar to this:
https://www.bunnings.com.au/tradeflame-propane-handyman-pinpoint-blow-torch-kit_p5910244
Double torch action is easier with an assistant who can understand instructions though with careful planning, wire binding and well placed solder pallions one can channel Chow Yun Fat and go in with two hands blazing John Woo style.

And for tiny things...
I’ve made earrings with a kitchen torch bought during an Aldi cooking gadget sale 🤣
One day I may try caramelising a creme brûlée with this one....

Also, well placed refractory bricks can be used to reflect heat back on the project. Build a shelter with them. Avoid house bricks or pavers as if they’re damp they may explode.

Somewhere above, maybe in Bob’s documents, there is a recommendation to work in dim light to better judge heat levels by the colour. I wear IR filter safety specs, it takes a little brain tweak to read the metal colour but does avoid retinal burns.
https://www.jewellerssupplies.com.au/product/27142-safety-glasses-all-terrain-green-5
 
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bob

1000+ Posts
Dad's jewellery torch is here, one of these....

Valtock2000small.jpg


Valtock_2000_instructions_small.jpg


I haven't tried it out, but it looks serviceable. Although you'd have to be wary of dribbles, burning metho is hard to see.... :)

Bob
 

shibuichi

Member
Dad's jewellery torch is here, one of these....

View attachment 134960

View attachment 134961

I haven't tried it out, but it looks serviceable. Although you'd have to be wary of dribbles, burning metho is hard to see.... :)

Bob
That looks more vintage than some of the tools I’ve inherited 😁 I’ve not seen one quite like that before.
Great you’ve got the original box. I had to do a quick search and a Valtoc 2000 with handle but no box is currently listed on fleabay.uk for a starting bid of £16.
 

PeterT

1000+ Posts
If I had to pay for gas I'd use an Orca (or similar). One of the key advantages of using 45% silver solder, is the low melting point, thus oxy-acetylene isn't mandatory.
 

shibuichi

Member
Heh. 45% silver solder....
I think I’d call that “extra easy.”
In silversmithing, the solder used for fabricating silver should be no less than 65% silver as lower silver content is a yellowish colour and the join is more obvious. Of course that doesn’t really matter for plumbing applications.

The two sources of recipes I have to hand for jewellery/silversmithing would be:
Hard - 75 Ag: 22 Cu: 3 Zn (Untracht) or 79 Ag: 14 Cu: 7 Zn (Wayne Guest)
Med. - 70 Ag: 20 Cu: 10 Zn (Untracht) or 72 Ag: 19 Cu: 9 Zn (Guest)
Easy - 65 Ag: 20 Cu: 15 Zn (Untracht) or 65 Ag: 23 Cu: 12 Zn (Guest)
 

1972Ren

The Comeback Kid
The two sources of recipes I have to hand for jewellery/silversmithing would be:
Hard - 75 Ag: 22 Cu: 3 Zn (Untracht) or 79 Ag: 14 Cu: 7 Zn (Wayne Guest)
Med. - 70 Ag: 20 Cu: 10 Zn (Untracht) or 72 Ag: 19 Cu: 9 Zn (Guest)
Easy - 65 Ag: 20 Cu: 15 Zn (Untracht) or 65 Ag: 23 Cu: 12 Zn (Guest)
Just as a matter of interest, I thought more silver made the rod 'easier' to use?

Anyway, thanks very much for all the comments.
Collectively they fill in the high level of ambiguity on the Net, regarding different rods.
 

shibuichi

Member
Just as a matter of interest, I thought more silver made the rod 'easier' to use?

Anyway, thanks very much for all the comments.
Collectively they fill in the high level of ambiguity on the Net, regarding different rods.
In precious metal soldering the higher silver content = higher melting temperature = stronger join.
“Easy” solder AKA “soft” has the lowest melting temperature but I find hard solder “easier” to use... I find it flows smoother.
As I said before, I’m unfamiliar with the tin/antimony solders or how their composition relates to melting temperature.
 
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Really good thread. Have learned heaps. Many thanks

Have been struggling with this particular black art for years, but never done enough to become really competent. The subtle tips from those who do it every day are gold

Andrew
 
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