Soldering

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A brief guide to soldering by Geoff

There are 4 areas we need to look at, they are:

(1) The metal

(2) The solder

(3) The heat source

(4) The flux

Let’s take each one separately and get to know how each one will affect us in soldering.

1. The metal i.e. copper. Copper like any metal will corrode in its own certain way when exposed to the atmosphere. (Iron or steel being ferrous will rust and turn red. Aluminum will turn powdery white and crumple) copper if left to its on devices, on a roof covered in copper will turn a beautiful bright, light, almost florescent green and stop at that coating. And in order to solder copper, this corrosion must be removed back to the base copper metal. (Remember to always keep your work fluxed, clean and shining that’s the big soldering secret). Thankfully, the copper pipe we get from the stores has only the initial stages of surface corrosion started and this can easily be removed with wire wool or emery cloth, but I find coarse wire wool is best to use. Clean the copper and all surfaces to be soldered, until they shine brightly and set them aside and don’t touch them with moist sweaty hands. As the salt/grease in the sweat will turn to carbon when heat is applied, not good for soldering (solder won’t stick to carbon)

2. Solder. Use new relatively clean bright looking lead free solder. LEAD FREE is most IMPORTANT for the purpose we intend to use it for

3. Heat source. As a heat source you really need a butane or propane torch/burner with at least a ½” nozzle. (I think even that is very under powered)

4. Flux. A general all round soldering flux is as good as any these days, they should all work well. The flux is pretty inert when you apply it at room temperature, but when heat is applied the flux will become very corrosive and will bite into and really clean the surface of the copper, especially when it has reached 100 degrees C plus, and the flux will make the solder really flow onto the copper surface and join where the flux has cleaned it. The flux can be easily burnt, by the torch flame, and turn to carbon which is not good for us. (more about this later)

Soldering Procedure .

1. Copper fitting usually comes in 2 types, end feed or solder ring. End feed by its very name means you feed the solder in via the end of the fitting and pipe join line. All new solder integral solder ring fittings have an integral ring of lead free solder inside and this will flow in a perfect ring around the join when they are cleaned fluxed and heat is applied. They cost more but if you are unsure about your joints, this is a good way to go to get good joins. I shall deal with end feed fittings for this topic.

2. Next cut, “dry fit” and check and clean all your pipes and fittings that you intend to solder

3. Flux them all up and smearing enough flux inside the female fitting and on the part of the pipe that will be going inside the fitting, (apply the same amount of flux to the copper parts as you would antiseptic cream to a cut finger) I personally apply a lot more. But that’s just my preference

4. Unroll a length of solder. A general guide as to how much each join takes is on (a 2” pipe). If you bend or kink the solder about 2 ½” from the end and when that has feed into the join that should be plenty in there. (Slightly more than the pipe diameter whatever join you are making. The same rule applies whether its ¼” or 6” it’s a good general guide)

5. Now assemble and set your pipe and fittings, light the torch/burner, and with your stick of solder at the ready. (For a 2” column pipe) Apply heat first to the pipe about 3 “away from the join on the top, the sides and the underneath as equally as you can until you see the flux sizzling at the join at least.

6. Then do the same on the fitting but not as long on the fitting. And certainly not on the join line if you can help it. (because that will burn the flux)

7. If you get too close to the join the flux will burn go brown and then black and carbonize. (burnt carbonized flux will ruin a good join) The trick is to be patient and let the heat move along to the join from about the 3” away from the join and then let this heat move into the fitting and out to your solder stick. So be careful and watch out for this, because solder won’t stick to carbonized flux on the pipe or join. If this happens to me. (Which it sometimes still does) I have a long stiff hog hair artist brush dipped in flux and I swish this over the join and it cleans the old carbon off and leaves it nice and bright again for the solder.

8. Things are now happening fast. Direct the heat away from the pipe and fitting. Now with your solder stick touch it to the top of the join line. Be patient and wait, let the heat get through into the solder. It should soften and squelch onto the join. Now take the solder away and apply more heat in the same sequence as before. The solder you applied will likely get sucked into the fitting. But don’t panic, continue your heating.

9. Now apply more solder and wait again, it will suddenly soften and run straight into the join. Now apply more heat to the fitting this will draw all the solder to the kink mark on your solder stick into the join. Solder will run and get drawn up into and evenly between the two copper surfaces. Just the same way sap on a tree will get drawn up between the bark and the wood evenly. This is called capillary action.

10. If there is any obvious gaps, heat and feed more solder in and just flash the heat across it just enough until it smooths nicely between pipe and fitting. (Don’t get hypnotized by the flame and have it pointing at the flux and end up burning it because it is so very easy to do) Back off with the heat and solder stick, and again be patient and let it cool enough for the solder to set (because the join and fitting can and will move if you are not careful) and that’s a big no-no if a 2” elbow ends up pointing the wrong way and ends up setting that way

11. While it is still slightly over hand hot but with the solder hardened use an old rag, wipe and clean off the old burnt flux, it will come off real easy when its hot like this


The master plumber who taught me said when soldering copper always think ahead and always follow the 7 “P’s” Principle. Which is:-

(1) Previous

(2) preparation and

(3) planning

(4) prevents

(5) pi** or pathetically

(6) poor

(7)performance

Hope this hasn’t been too boring guys but some people just don’t know how to solder properly, and this is for them and :- (Remember to always keep your work fluxed, clean and shining that’s the big soldering secret)