Silver soldering fail - How to recover?

My brew partner and I decided to silver solder our kegs. The first joint came out horrible... Its got a lot of big blobs of solder and there is kind of a small "cavity" in it. We haven't water tested it to see if its water tight yet. The rest (we did 8 total) turned out really nice and all look great.

I think we didn't use enough flux, and overheated the coupling instead of the general area.

Does anybody have any experience trying to "re-do" a silver solder coupling joint?

I'm wondering if I can get the solder flowing, try to wick it away or suck it out, sand everything, re-flux, and re-solder.

Thanks guys!

For sure you can do it again. Heat it up, remove the part, clean all of the residue off of the part and the keg, and do it again. Take the time to clean both keg and part really well before you try it again

Just a guess but did you use the correct flux?

I also heated up the fitting not the keg when I did mine and it came out fine.

You can definitely start over once everything is clean.

Use a heavy grit sand paper to give the solder a place to stick.

Re-solder! It's a lot easier to deal with than a bad weld!

Thanks I think I'll give it a try.

Any advice on how to get the fitting out of the bulkhead? Its held in by the dimple really snug and I wonder if I'll have trouble getting it out once the solder is fluid.

Thanks!

I had to get one out too. Have your dimple tool all ready to back the fitting out, heat the fitting as you normally would-letting the solder liquefy, back it out while hot. It worked for me. Good luck!

You could try cleaning all around the joint then while heating it to liquefy the solder brush more flux on with an acid brush soaked in flux. That worked for me when I had a spot on my attempt at soldering stainless didn't take to well. It also works all the time for me when sweating copper pipes that have issues sucking the solder in.

If the fitting is still in the keg dipple, I would suggest heating till the solder flows and then use a small stainless brush to clean the joint off.

This will get rid of the excess solder and any oxidized material on the surface.

Then just apply new flux, heat, and reflow the joint with solder.

Laying the keg so the fitting is horizontal will allow gravity to work for you by helping to carry the solder away from the joint.

Another easy way to desolder is to heat until it's liquid then drop the keg from a height of 4 inches onto a concrete floor.

Bobby_M said:

Another easy way to desolder is to heat until it's liquid then drop the keg from a height of 4 inches onto a concrete floor.

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.....At times like these... I wonder... Is Bobby Fking with us.... to see if we will actually do it....


or is he talking from experience.... It's so out there I'm guessing the second

CCBrewer said:

.....At times like these... I wonder... Is Bobby Fking with us.... to see if we will actually do it....

or is he talking from experience.... It's so out there I'm guessing the second

Click to expand...

I was thinking the same thing...the experience part, not the F'ing with you...

Cheers!

Trust me, it works. No matter what I'm trying to get solder off of, as long as it can take a quick hit to the workbench, I do that rather than using wicking rope (this is a mesh of fine copper used to wick solder away from work). Just as an example, when building my test control box, the panel mount 120v outlet had solder on the spade terminals. I put heat on it, WHAM!!! no more solder on there. Of course be careful, wear eye protection and stuff like that. Hot solder splashing on you isn't fun.

Bobby_M said:

Another easy way to desolder is to heat until it's liquid then drop the keg from a height of 4 inches onto a concrete floor.

Click to expand...

Thanks for the awesome responses guys. I'll see what I can do when I've got some time to mess with it. We tested it yesterday for kicks and it does hold water.

We used Harris Liquid Stay-Clean flux and Harris Stay-Brite silver solder. The pair worked amazingly well when we used enough, but the bad one was #1 out of 8 fittings. 2-8 look great.

I like the idea of dropping it a few inches. Since there won't be any flux on the oppose side of the keg wall and it'll be cold I'm guessing the flux won't stick.

Bobby_M said:

Trust me, it works. No matter what I'm trying to get solder off of, as long as it can take a quick hit to the workbench, I do that rather than using wicking rope (this is a mesh of fine copper used to wick solder away from work). Just as an example, when building my test control box, the panel mount 120v outlet had solder on the spade terminals. I put heat on it, WHAM!!! no more solder on there. Of course be careful, wear eye protection and stuff like that. Hot solder splashing on you isn't fun.

Click to expand...

I'm an Electrical Engineer so I've got some solder wick in my electronics repair toolbox but I didn't feel like using up $10 worth of wick.

Thanks again for the responses Bobby. When we first started moving to kegs from our stove-top partial boil setup we watched a bunch of your youtube videos. We actually bought our sight gauges and thermometers from you last week and plan on putting another order in soon. Keep up the great work, your wealth of knowledge has been greatly appreciated.

Hey guys, I figured I might as well post an update.

I followed Bobby's recommendation of dropping the keg and it worked great. Here's what I did:

1. Laid down a big sheet of leather on the cement to stop the cement from scratching my keg. This is pretty thin and firm leather that won't absorb much shock.
2. Heated up the keg and coupling until the solder began to flow.
3. Flipped it so the coupling was facing up and smacked it hard on the leather. As predicted the silver solder splattered on the other side but did not stick. It came off with a damp cloth.
4. Cleaned up the residual silver solder with increasingly finer sand paper until it was a nice clean surface for the coupling to pull through. Originally there was still a rough thin layer of silver solder.
5. Re-soldered a new coupler in the hole. The original coupler was looking pretty pathetic at this point. It was purple from the repeated heating and was covered in a thin coarse layer of dried solder.

Attached is a photo. I haven't scrubbed and cleaned it up yet but I'm very happy with the final result. It is perfectly water tight now.

Thanks for all the help!

Nice work!!

My first attempt at soldering this evening was a fail too. Glad to find this thread...that it is worth desoldering and trying again. I'm thinking that I must not have had the piece completely clamped tight enough all around. I had a really nice solder all but 10 degrees. Then I tried heating it up and just closing up that gap...it kept eating solder. I added flux and it kept eating more solder. So frustrating.

Where you putting the heat directly on/under the spot that was eating the solder? Try ruffing up around that spot with some sand paper and a little more flux then heat the pot near the spot and let the heat drift to the spot to slowly melt the solder. The key is to heat slowly and just enough for the solder to take. I had 2 joints with small problem areas like that and it worked out well for me. I even used this to seal up 2 rivet holes on a lid that I removed the handle off of.

After cleaning the surfaces with sandpaper you need to wipe down everything with a solvent like alcohol.

Any residual oil, grease, wax, or other contaminate can keep the solder from flowing properly.

processhead said:

After cleaning the surfaces with sandpaper you need to wipe down everything with a solvent like alcohol.

Any residual oil, grease, wax, or other contaminate can keep the solder from flowing properly.

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Yep. I used mineral spirits.

bannerj said:

My first attempt at soldering this evening was a fail too. Glad to find this thread...that it is worth desoldering and trying again. I'm thinking that I must not have had the piece completely clamped tight enough all around. I had a really nice solder all but 10 degrees. Then I tried heating it up and just closing up that gap...it kept eating solder. I added flux and it kept eating more solder. So frustrating.

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That is exactly what happened on mine when I did the original post. It must have heated unevenly and burned off the flux on the bad side because despite focusing more heat on that area it never flowed. I fed a few inches solder in trying to bridge the gap when it was hot but that never seems to work with a flux-free solder.

The only downside to redoing it and completely removing the coupler like I did is the coupler that was originally installed is so nasty between heating, scraping, and sanding that I didn't want to use it. http://brewhardware.com has them for pretty cheap too (under Fittings/Camlock). If I was about to redo mine I'd definitely start fresh again.

Mineral spirits worked well to clean it up for me. It looks beautiful.

Good luck fixing it! Like many DIY projects, being nervous about screwing something up held me back from attempting the fix but visiting some forums usually gets rid of that anxiety better than a few homebrews, for better or worse... Lol

I am trying to fix a TC fitting. How about a hammer to the backside of the fitting (on the inside of the pot)? Will that knock the solder off?
I would use another TC ferrule, because this one is purple now.

If solder tinned to kettle properly, a hammer will not free it up, at least not without damage. Best bet is to re heat, clean everything up and try again. Good quality flux, preferably high acid flux designed for stainless, is a must. The discoloration can and should be cleaned up, as it means stainless components have moved to surface (nickle, cadmium, etc) But should clean up with acid treatment or scrubbing. Nitric acid products for cleaning stainless welds available from welding supply places.

Dland said:

If solder tinned to kettle properly, a hammer will not free it up, at least not without damage. Best bet is to re heat, clean everything up and try again. Good quality flux, preferably high acid flux designed for stainless, is a must. The discoloration can and should be cleaned up, as it means stainless components have moved to surface (nickle, cadmium, etc) But should clean up with acid treatment or scrubbing. Nitric acid products for cleaning stainless welds available from welding supply places.

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I know cold solder won't free up - I meant that instead of heating it up and then dropping it onto the ground, can I just remove the hot solder by hammering it from the inside of the kettle?
What other methods exist to remove solder?

Maybe heat and remove ferrule with pliers or tapping, while hot. Excess solder can be wire brushed or wiped with rag while hot to remove. Good to use welding gloves or similar. Any that is well tinned on, a thin layer sticking to metal, shiny, no contaminants, can be left in place as it will help accept the new solder on your next try.