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Thread: Soldering technique?

  1. #1
    DIY Senior Member kcodyjr's Avatar
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    Question Soldering technique?

    I have a good hand for soldering wire, but nobody ever showed me the right way to use a torch.

    I'm heating the fitting, on the opposite side from where I'm holding the solder, and letting the flame wander around half an inch or so. I'm holding it just close enough to see the flame break around the fitting.

    By the time the solder starts flowing, the copper has turned rainbow colored.

    Am I overheating? How to avoid it?

    Also, should I be using some kind of cleaner after the solder cools?

  2. #2
    Nuclear Engineer nukeman's Avatar
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    Did you clean the fitting and pipe before soldering? Are you using flux? What kind of flux?

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    DIY Senior Member kcodyjr's Avatar
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    120 grit sandpaper, outside of the pipe for 3-4 inches, inside of the fitting all the way in to the ridge, until it's totally bright.

    Bernz-o-matic water soluble lead free plumbing flux, a thin even coat by brush to about 1 1/8" on the pipe, all the way to the ridge inside the fitting. It's 3/4" pipe.

    I am seeing a solder ring come through when I look inside the fitting from the other end. They look mostly clean with some black spots that look more like burnt flux than gaps. That ring should indeed be visible, yes?

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    Forum Admin, Expert Plumber Terry's Avatar
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    I like heating evenly. It's good to get the back side, but you need to get the opposite side too.
    The pipe only needs sanding where it goes in the fitting. And even then, new pipe with flux often doesn't need it. I do have emory cloth handy.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    It's easy to overheat and burn the water soluble fluxes when you aren't familiar with them. I find that the tinning flux (stuff has powdered solder in it) tends to work well and the older stuff. You do need to move around the fitting, then, once it's hot enough, you can likely remove the torch as you add the solder, or at least ensure it's not in the flame. Get the inner point of the flame on the fitting, it's hotter, and you'll get things up to temp faster without burning out the flux once you get the feel for it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member kcodyjr's Avatar
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    Jim, so if I've burned the flux, did I ruin the joint?

    Terry, yeah, that extra couple inches of sanding is just because I'm palming the paper and wrapping it around the pipe. I'm only fussing over the top inch or so. New pipe with flux doesn't need sanding? I thought copper oxide wouldn't bond, does the flux eat through it? Where can I read up to improve my understanding of the theory in this area?

    Sounds like the basic flaw in my technique is that I'm holding the solder on one side and the heat on the other, like I would with wire. I'm reading that I should heat the fitting on all sides, then put down the torch and push the solder into the joint. Is there anything visible or smellable to tell me when the moment is right, short of roasting the metal into a kaleidoscope?

    I haven't put any of these assemblies under pressure yet, but there will be a garden hose adapter in their future before anything gets installed to the home. I'm not sure whether to expect they'll hold or not since there's obviously some burned flux in the joint. Either way though, I'd like my results to look more workmanlike.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Do your existing joints have a nice shiny ring of solder at the pipe/fitting junction, or does it have black specs in it? If it is continuous solder, it's probably okay. If you have black specs and it is not smooth, you may want to take it apart and redo.

    When you are heating the joint, first you'll see the flux start to boil...pull the torch away, and touch the solder to the joint...it will probably flow, if not, return the flame for a bit more, then try again. Actually, you can try to see if it is hot enough to melt the solder any time, just keep it out of the flame. If it flows, it's hot enough. The solder will sort of act like a spot weld before it flows, and that tells you that you are getting close to the proper temp to make the joint. You've probably noticed that when soldering wire...the solder wire will sort of stick, then as you add more heat, flow.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member kcodyjr's Avatar
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    Some have specks, some look clean. OK, looks like I have some rework to do...

    In cases where the fitting isn't coming apart, such as the threaded side of a union that had to be tapped on before soldering, is there anything I should do beyond heating it up and adding more solder until the ring looks clean?

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
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    If you've burned the flux out, you really should take it apart and clean it up. It does not sound like you've run water through it yet, so any joints that are good, can stay that way. Once water has gotten into it, you have to take it apart if it leaks.

    Wait for one of the pros...sometimes, adding some more flux and solder will resolve it, but it is not a certainty...a proper joint has 100% coverage of solder throughout the whole fitting/pipe interface. Burnt flux will prevent that, and a leak may not show up for awhile, if ever, depending exactly on what's there.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member chefwong's Avatar
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    I'm not a pro but I would hesitate reheating/attempting to add solder to a existing joint...IMO. Copper fittings is cheap in the long run of a reliable connection.

    Sounds like you're overheating it before or during the soldering process.

    Get some scrap pieces out, start getting a feel for when a joint is properly hot enough and then solder away on what's really needed.
    I think once you have the ~feel~ down on when it's hot enough and it's just a matter of applying solder (something just adding a bit more heat to finesse the joint), you're good to go.

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    DIY Senior Member SteveW's Avatar
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    I agree that sounds like you are overheating the joint.

    What size pipe are you soldering a fitting to? If 1/2", or even 3/4", it will only take 5-10 seconds to heat the joint hot enough, depending on the torch.

    Also, make sure you are heating the fitting, not the pipe.

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    DIY Senior Member kcodyjr's Avatar
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    It's 3/4". 5 to 10, really? I wasn't standing there counting mississippis, but it seemed like 40-50 before the solder melted.

    So, I'm slowly creating a hot spot that's burning the flux before the heat spreads to the other side. Chaaaahming.

    Those union joints are $9 each, not so cheap... I'll have to figure out some way to suspend it by the fitting so I can heat it up and whack the pipe free.

    Correct, no water through it yet.

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    DIY Senior Member dj2's Avatar
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    1. With MAPP gas you need 10-15 seconds, not 50 seconds. If the pipe turns red - it's overheated.
    2. I watch the flux: when it start sizzling, that's an indication that it's ready, and I slowly get the solder to touch the joint - it should get sucked right in. For 3/4" pipes all you need is 3/4" long solder section.

  14. #14
    DIY Senior Member kcodyjr's Avatar
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    Quote Originally Posted by dj2 View Post
    1. With MAPP gas you need 10-15 seconds
    I'm using propane, not MAPP. Should I be?
    Last edited by kcodyjr; 11-19-2013 at 08:17 AM.

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by kcodyjr View Post
    I'm using propane, not MAPP. Should I be?


    I would get a real torch and some real flux.

    Make sure your solder is clean.


    Good Luck.
    Theory only works perfect in a vacuum.

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