Soldering technique?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by kcodyjr, Nov 18, 2013.

  1. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    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. nukeman

    nukeman Nuclear Engineer

    Messages:
    708
    Location:
    VA
    Did you clean the fitting and pipe before soldering? Are you using flux? What kind of flux?
  3. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    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?
  4. Terry

    Terry Administrator Staff Member

    Messages:
    14,786
    Location:
    Bothell, Washington
    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.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    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.
  6. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    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.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    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.
  8. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    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. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,817
    Location:
    New England
    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.
  10. chefwong

    chefwong New Member

    Messages:
    710
    Location:
    District of Columbia
    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.
  11. SteveW

    SteveW DIY Senior Member

    Messages:
    1,052
    Location:
    Omaha, NE
    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.
  12. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    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.
  13. dj2

    dj2 Member

    Messages:
    399
    Location:
    California
    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. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    I'm using propane, not MAPP. Should I be?
    Last edited: Nov 19, 2013
  15. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX


    I would get a real torch and some real flux.

    Make sure your solder is clean.


    Good Luck.
  16. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,786
    Location:
    Long Island, NY
    I've had no trouble at all with propane for 1/2 and 3/4 inch tubing and fittings, but the first time I got a MAPP torch and gas, it was like WOW. I was able to do 3 inch copper without too much trouble. In the past I had worked with torches burning regular acetylene in MC and B tanks. MAPP is easy to work with and safer than straight acetylene. Everything needs to be nice and clean, and fresh flux used. I never had a problem sweat soldering, but I've seen other people make a mess the first time they tried it.
  17. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX

    It helps if you use the correct tip.


    tip.jpg


    I like to get on the heat and off of it quick.


    Toxic Flux and the works in the solder works best, but it may kill you in 100 years.
  18. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    Okay, I'll bite, please define "real" in a way that will be useful when I walk into Lowe's?
  19. dj2

    dj2 Member

    Messages:
    399
    Location:
    California
    Yes you should. Your propane torch is not to be used with MAPP gas, so buy the whole set.

    Practice before you do your job. Be careful, it burns high very fast. Have a wet rag and spray water with you. To hold fittings use a chanel-a-lock.
  20. nukeman

    nukeman Nuclear Engineer

    Messages:
    708
    Location:
    VA
    There shouldn't be any prob using propane. I've used a propane torch many times without issue. I also have a MAPP torch and an oxy/mapp for brazing.

    I've had good luck with Oatey No. 95 Tinning Flux (available here at HD, but usually only in a kit with solder and flux brush in my location). You are using plumbing solder, correct?

    I'll clean up both ends real good, apply flux to both ends, and then heat the fitting. I usually go for the tip of the inner dark blue flame just touching the fitting (hottest part of the flame). I may apply to mostly one side of the fitting, but may rotate it a bit. For the smaller stuff (1/2", 3/4"), this doesn't seem to be an issue. One the flux starts to bubble, it is usually hot enough. Start to touch the joint with the solder. It should melt and be pulled into the joint. You can cut the heat before this point as long as the fitting is up to temp.

    As long as the joint is clean, you have the right flux/solder, then it is just a matter of controlling the heat. You don't need a new torch unless you are using some micro-torch normally used for wiring, etc.
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