The dark art of copper soldering

[DLaing]

I can happily solder copper pipe together so that it doesn't leak but the joints always look, well, amateurish. I tend to use the pre soldered variety and always end up with a blob of solder at one point or another.

What's the secret of getting a perfect visible ring of solder all around the joint?

I've tried using non-soldered joints and separate solder but it always seems such a fiddly job: heat the joint, press the solder, nothing happens, heat a bit more, solder melts too much, etc. It there a nice technique like heating very gently etc that I'm missing?

Any tips greatly appreciated.

 

[AdamW]

I have never tried solder joints myself... I always plan to and then lose my bottle and buy "wuss-fit" joins.

However, I have read that the easiest way to do it is to use pre-soldered, but add more solder.

 

[Bahco]

Use end feed fittings.
Flux pipe with Laco flux, apply heat, when flame changes colour to green (or just before) apply lead free solder which should run immediately.
Remove heat and brush joint with a small brush which will remove excess solder. Allow to cool then clean joint with soapy cloth.
Should look professional
I always tend to get problems with pre soldered and will not use now.
Practise and practise and you will become confident with end feed

 

[Malc]

You need to clean the mating surfaces - wire wool is good (but not with brillo pads as they include soap ). Add flux to both and mate. Heat evenly until flux bubbles then add solder which should wick into the joint. Excess solder will form a blob at the lowest point so for a perfect join stop adding solder just before that (but how you tell I don't know, I settle for a blob to be sure the joint is complete).

 

[ChrisR]

I think any sort of brush will melt or burn, but you can wipe excess solder off with a rag (not synthetic) or some kitchen roll.

SOunds like you may be adding solder to solder-ring joints. Not necessary, though many do it.

 

[billythekid]

heat the pipe and not the fitting with yorkie fittings, take the heat off when you get the first showing of the "silver ring" Straights and bends are easier than tees to get a nice looking finish with as you are only heating two sides. Always clean your joints afterwards with a damp cloth to stop them from turning green with the flux run.

 

[AdamW]

So do you put all the pipes into the fitting before applying any heat and do them all at once, or do you go one pipe at a time?

I presume it is the former, but would be useful to know.

 

[billythekid]

all the pipes go in before soldering, else some solder might run into the other ends and you wont get the pipe in! Do them all at once and use plenty flux.

 

[ChrisR]

We'll all disagree on something on this one. I'd say use a minimum amount of flux. Put it on with a brush (Laco 2 oz pots have the brush in the lid). All you have to do to cleaned copper is wet the surface with flux. Laco actually say "wipe off excess flux", which I've never seen anyone do!

The reason is that while the excess flux is on the joint boiling, it's holding the temperature down near the boiling point of the flux. But when the energy of the blowlamp doesn't get used for boiling any more cos the flux has all boiled off, the temperature of the copper rockets suddenly, and the surface oxidises quickly. In that state it won't take solder.

It obviously DOES matter how strong your flame is, how adept you are and so on, but it's something beginners should be aware of.

 

[oilman]

I agree with ChrisR on this. MINIMUM flux. There is a problem with lead free solder, (HighMeltingPoint solder in the electronics industry) the flux has to get so hot it is not far off baking point and forms a hard deposit inside the pipes which later breaks away and wanders about looking for a radiator to corrode.

I have tried solder paste on solder ring and end feed fittings. It goes on nice and thin and makes it easy to make reliable joints. It's a bit more expensive but that's nothing compared with the overall cost of the job. Wipe the finished joint with a paper towel, and it looks fine.

I think I'll try a lime mortar and tung oil mix tomorrow

 

[ollski]

yes minimum flux or else it will run all down the pipe and the molten solder will follow it....you only need to flux where you actually want the solder.

 

[dan21mag]

you flux the pipe ONLY, NOT the fitting, remove torch and quickly
touch back of joint to see if solder runs, if not repeat the heat, once soldered DONOT wipe with cold cloth till pipe has cooled by itself...easy

 

[ChrisR]

I always put the brush over the pipe and the socket, but only enough to dampen the surface.
Once the solder has frozen you can chuck it in a bucket of room-temperature water if you want to, solder recrystallizes at room temp.

Knew we'd disagree somewhere!

 

[bripl]

the tidiestway of soldering is use non aggresive flux telux/yorkshire,clean pipe/fitting apply flux with brush on pipe rotate fitting ensures even coverage wipe off excess apply heat to fitting move heat along to pipe this will draw the solder out to a visable ring move heat to other end and repeat,you should not need to add solder as a york fitting contains three times the amount req,but belt and braces add a dab wait for joint to cool and clean with a damp cloth.if using end feed add solder when flux has bubbled/evaporated this way you avoid runny snots which look very proffessional with nice green streaks.i perssonally do not like laco/everflux/powerflow as they are too aggressive if not cleaned off properly rots pipe/rads/heat exchangers.