soldering gone black

20 Jun 2012
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United Kingdom
I have been soldering some complicated piping. I have done quite a lot of 15mm and 22mm Yorkshire fittings around the house and it has gone fine. I am now, connecting 35mm straight connector to 35-28mm reducer to 28mm straight connector with 15mm T to 28mm 90 then another very close. The whole lot crammed together in about 250mm all with end feed fittings. My initial attempt was not a pretty sight. Things got very hot and nasty with burnt flux and the joints wouldn't run.. I changed the gas on my blow torch for map gas. Can anyone give me a clue how to manage this successfully
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You sound like you have done a fair bit of soldering so I won't bore you with basics

Dipping your solder in the flux can help you to get a joint to run.

The rest is obvious like soldering the smaller joints first, keeping an even heat, heating the fitting and not just the joint where the solder runs, if you struggle a bit you could re affirm the joint by running some flux with your brush around it and then apply another quick burst of heat.

On the 35 mm the Mapp will help, on the othervfittings you'll have to be careful not to burn the flux, keep the burner moving about six inches from the work and keep dabbing with the solder until it's ready to run.

I've got callouses on my fingers now :p
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You got it too hot !

The solder wont go in to the fittings if they're too hot it just runs off.

Take it apart and start again.....I never use mapp gas too fierce for me personally, have used it and got some cylinders but my preference is propane.

Hint :
When you see the flame is going green beyond the fitting its the copper "burning" its too hot !
More flux!

No need for mapp gas, regular propane is fine.

Dont have your flame absolutely roaring, keep it at a steady pace, and keep your solder touched on the joint so you don't over heat it.
Obviously there are some variations in soldering techniques coming to light here....

my two old pennies worth is (on 35mm copper) Use Mapp Gas, get some heat into the pipe (don't just concentrate on the fitting), by all means melt an 1/8" of wire solder onto the pipe where it enters the socket, as it disappears into the fitting judiciously add another 1" or so.

Unfortunately, with the price of copper pipe&fittings practice is a dear hobby.

Can you place a heat mat behind the pipe to reflect additional heat back onto the fitting?

invest in a bullfinch, change the nozzle for whichever situation you like, keep a rothenberger for the small/awkward ones ;)
Rule of thumb .........amount of solder required in an and feed fitting is roughly equal to the dia of the pipe.

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