(Silver) soldering

Started by Kenny · 19 replies · 15,940 views

Kenny

23 Jun 2025, 11:12

Only soldering I have experience with is electronics component soldering. Did some gas welding back in school and that's a life time ago so I have a few, hopefully not too stupid, questions:

How is gas welding different from hard silver soldering? Seems very similar to me. A gas and a flame

Second, can only silver solder be used? I have seen things like some brass or phosphor bronze. Can that be used?

Only silver solder wire/sticks I have found around here are the flux coated ones. Are they ok too? Better/worse than bare wire?
I'm guessing one could just remove the flux coating and use separate flux?

Ken

uuu

Reply #1 · 23 Jun 2025, 11:29

Welding usually refers to a technique where the base metal is melted. And can involve the introduction of additional material to fuse into the melt.

With soldering - it's at a lower temperature - the base metal does not melt, the melted solder amalgamates with the base metal which remains solid.

I've only ever used bare sliver solder wire and a separate flux. I use a big propane torch for heating - oxygen is not required to get to the temperature required.

You can use brass wire - the term brazing particularly refers to this - although the term can also be applied to soldering. But it's at a higher temperature than silver soldering - still not melting the base material.

Wilf

redhouseluv

Reply #2 · 23 Jun 2025, 12:08

Hi Kenny

I only just started to cut my teeth on silver soldering recently and had to buy the equipment and materials. There are a couple of videos which I was forwarded by Jason when I was doing a build which were particularly useful (you can also see the errors I made

):

https://www.modelenginemaker.com/index.php/topic,12095.30.html

I'm no expert, but am slowly finding my way and becoming more confident the more I do - good luck, with it.....

crueby

Reply #3 · 23 Jun 2025, 13:21

And the term silver solder is one that is a bit vague. There are soft solders with a tiny bit of silver that the manufacturers call silver solder. The main use of the term is for hard solders with around 40 to 60 percent silver, melting temperatures above 1000F.

The coated rods are not used much for small model work, thats more a convenience thing for large work. Better for model work is the paste flux, often sold as powder you add water to, that you spread on the joint before heating. That prevents scale from forming as you heat. Silver solder comes in many forms, I like the fine wire that can be cut and laid on the seam as well as added in by hand after heating.

As you say, some sort of gas and flame to heat. Usually a propane or butane flame, oxy acetaline is too hot for brass parts unless you are experienced with it. Silver soldering is a lot like brazing, and there are several alloys of the solder in the jewelry world to match colors of the parts being joined.

rklopp

Reply #4 · 23 Jun 2025, 17:24

Aside from absolute cleanliness and liberal fluxing, I've learned a few helpful practices:

Make the parts melt the silver "solder." Avoid heating the silver solder directly with the torch, whether solder is pre-placed or fed by hand.
You really need red heat.
Paint White-Out correction fluid on the parts to make a neat border for the solder. (This is my most useful learning for neatness.)
Have some sort of acid pickle ready. I use 1 part muriatic acid swimming pool acid added to 10 parts water. I understand some use citric acid from home-brewing suppliers or the pharmacy. Pickling saves a lot of hand work with ScotchBrite or abrasive paper. Do not put hot parts in acid. Wear appropriate PPE.
Don't try to solder a complex assembly all in one shot. Go step by step and pickle in between.
Make sure a joint won't slip out of place while being heated.

Kenny

Reply #5 · 23 Jun 2025, 17:43

Only silver stuff I have found is marked L-Ag 45 Sn, 1.5 mm and flux coated. I'm thinking that 1.5 mm might be a bit thick for small part work?

There there's also square 2x2 mm rods named phosphor copper L-AG 2% and basically looks like copper. These are not coated. Cost a lot less than the coated silver. 2x2 mm is for sure huge for our type of work.

crueby

Reply #6 · 23 Jun 2025, 17:43

Great list of tips!

For pickle, two other options are either Sparex2, available from jewelry tool suppliers, or just kitchen type 5% white vinegar. Niether are as dangerous as the stronger acids, they just take longer to work. The vinegar is sliw but available at the grocery store, and can be flushed down the drain when its spent. I have some plastic screw lid jugs I keep my pickle solutions in, to keep them from evaporating when not in use.

crueby

Reply #7 · 23 Jun 2025, 17:47

Quote from: KennyOnly silver stuff I have found is marked L-Ag 45 Sn, 1.5 mm and flux coated. I'm thinking that 1.5 mm might be a bit thick for small part work?

There there's also square 2x2 mm rods named phosphor copper L-AG 2% and basically looks like copper. These are not coated. Cost a lot less than the coated silver. 2x2 mm is for sure huge for our type of work.

What part of the world are you in? Jewelry tool supply houses carry the wire solder and fluxes. I have even gotten some off Amazon. For flux, the Harris Black or Harris White are good, as is the Tenacity 5 flux. Depends on the country what brands you can find. For solder, the Easy, Extra Easy, and Medium grades are great, the easier the lower the temps needed and the easier they flow.

AVTUR

Reply #8 · 23 Jun 2025, 19:01

Kenny

Have a look at CuP Alloy website, https://cupalloys.co.uk. It is a mine of useful information. They can supply everything you need. I am sure they will export to Finland. Their cleaning salts, pickling acid, is citric acid probably with a biocide.

I find silver soldering immensely satisifying. However I do it out of doors since a propane torch gives out an awful lot of heat. This means soldering is dependent on the weather, windless days. Start with brass, copper or bronze. Steel, particularly stainless, is a little bit more difficult.

I could go on but have fun.

AVTUR

Kenny

Reply #9 · 23 Jun 2025, 19:37

Quote from: AVTURHave a look at CuP Alloy website, https://cupalloys.co.uk. It is a mine of useful information. They can supply everything you need. I am sure they will export to Finland. Their cleaning salts, pickling acid, is citric acid probably with a biocide.

Wow, awesome! Thanks for the link AVTUR! Looks like they do ship to Finland and even with exchange rate and customs fees it still looks like it should be a better deal than buying what I can find here. Plus they have a real selection of stuff. Will have to explore it more but it looks like this will be the source when it comes to silver soldering

Admiral_dk

Reply #10 · 23 Jun 2025, 20:40

Interestingly list - I could have sworn, that our Teacher back then was VERY insisting in that you have ruined your Silver Soldering if you got it Red-Hot ....
Even though we did it with a Acetylen-Oxy Torch we had maximum temperature as Straw (yellow) ....

Oh - well that might either be down to the specific Solder, Flux or bad Memory ...

Per

pirmin

Reply #11 · 23 Jun 2025, 20:42

for realy fine jobs i use jewelery grade silver solder, it can be purchased in 0,5mm and 1mm thick wire rods, or as sheet, ranging from 0,2 up to 0,5mm thicness.

as mentioned above some pickles can be made easily at home, Citric acid from the baking supply section in the supermarket works well for me ( powdered citric acid, it just needs to be mixed with water and always make it hot, hot pickle workds quicker! )

another option would be Alumn Salts, they are now prefered by jewelers over the Acid solutions, it is less harmfull.

Randy

Reply #12 · 8 Jul 2025, 10:48

Kenny Have a look at Mc-Mastercarr that is where I buy my silver solder and flux.

mike81

Reply #13 · 18 Sept 2025, 06:40

Quote from: Admiral_dkInterestingly list - I could have sworn, that our Teacher back then was VERY insisting in that you have ruined your Silver Soldering if you got it Red-Hot ....
Even though we did it with a Acetylen-Oxy Torch we had maximum temperature as Straw (yellow) ....

Oh - well that might either be down to the specific Solder, Flux or bad Memory ...
e]
Red heat is necessary. Flame should be placed on thickest part . I use 20% vinegar for a pickle. Works well and fairly quick. Cadium is in some solders, makes the solder flow easier but is a health hazard. I would stick with cadium free solder. Propane is hot enough for most work. Your teacher was partly correct, you can overheat the part and the solder will not work. Silver solder is also called hard solder as opposed to plumbing solders that are soft solders. Some solders are labeled Silver Bearing Solder, this soft solder for plumbing and not a hard solder.
Clean the solder before use by pulling a scotch Brite pad thru the wire. Flux the joint and the wire. Whiteout ,the typewriter eraser fluid will keep the solder from adhering to areas that you do not want solder to stick.

tghs

Reply #14 · 18 Sept 2025, 10:22

some great advice here,, not much to add,, if you can get Mapp gas it's a little hotter than propane,, fire bricks to suround the work helps heat things better.. I silver solder in a darkened room, it lets you see the glow of the parts and where more or less heat is needed,, to get a good joint all parts need to be heated the same, solder flows toward the heat.. and as always clean clean parts make for good joints