Hey Gang,

So I'm finally getting into silver-soldering (it's technically brazing but my coworkers like to raze me when I get technical).

I've got the basics down and am making good, solid joints.

But what I need now are some tricks and tips on how to make joints that not only work but look perfect (our project requires copper greater than 1" to be silver-soldered).

For example, after I silver-solder a joint, I clean it with a wet rag and some sand cloth to get the sooty stuff off. But the hub of the fitting still has a chocolate-milky appearance to it. What can I do to avoid this?

I'd also like other tips and suggestions that y'all have learned over the years.

The best way to perfect anything is to practice. Get some scrap and put it together in all type of conditions.
Good Luck
SouthernPlumber

The old school used to say get it cherry red. Actually you need to get it just at cherry red. Too much heat will cause imperfections inside of the joint. (honeycombs) I like to get the entire joint hot before applying the brazing rod. If at all possible always start at the bottom first. This will push the air out as the rod draws in. If you start at the top air bubbles can be trapped inside of the joint causing imperfections. I like to braze joint all around then apply a heavy cap right after. Always inspect all around the joint upon completion. Use a light and mirror if neccessary. Most leaks on brazing can be visually seen before a test is applied. GOOD LUCK

what are you using for flux?? oxy acetlyne torch with a pin point flame with the inside smaller blue flame touching the work. as high tech says heat to just cherry red not too hot. quench joint with clean water. clean pipe and fitting with rough sandpaper prior to brazing. and lastly.. if the flux is too dry, thin it with clean water, don't spit in it. (don't laugh, lots of guys do that)..

Sounds like he's talking about using the soft 'Clean & Bright' since he said he's cleaning up the joint with a wet rag...

I just use jersy gloves for that and regular soldering. You can't clean up a brazed joint with a rag. A little joint discoloration is normal but too much discoloration means too much heat. I know they probably taught you to do a figure 8 with your oxy/acet flame, but what works better for me is to do a in/out with the flame tip. Close for the initial heating and pull it back to keep it hot etc. Try that when you practice.

I don't trust quenching a soft silver joint, I only quench braze rod joints. Do check em with a mirror/light.

You can't avoid the discolor on the fitting that is caused by oxidation when heating to the temp. that is needed. The only thing you can do is steelwool it after cooling and if you were in the Navy I would say use a little Brasso on it to shine it.

I totally agree with Hytech's heavy cap idea. I do it by laying the solder right onto the joint and slowly let it wrap aorun to make a perfect cap. It ends up looking like a smooth welded joint and cleans up easlily with a wire brush.

It uses more solder ($$$) but looks great and adds to leak protection if there were to be somthing else in the joint you do not know about that went wrong.

i'm realy confusaed here?are you talking brazing(1000degree heat+silver bearing filler rod) or soldering?you know,clean,flux solder (700 degree)ect.brazing does noot use flux except between dissimeral metales like brass to copper.also you never shock a brazed joint while hot,you can crack a joint.they say not to do it to a solder joint but i've tons of them and never had any problems

Without flux or a self fluxing filler, how do you control damage caused by oxidation?

[www.copper.org] has a handbook that explains copper and its assembly fairly well.

it depends what type of rod you use, sometimes you need flux sometimes you don't. I think silphos rods you don't have to but could be wrong, all I know is I have done it both ways but now only without flux. speeking of flux, use it on your joints and rub it in with a brush while its hot and it will take the black away. I also do this on soldered joints sometimes if I discolor the fitting but be sure to wipe the joint because it will turn green. I have bought copper spray paint(sound bad I know) for my hydronic systems in boiler rooms, makes all joints look great but be sure to hold something behind it to protect the wall. it sounds scabby but it works

I managed the brazing section of one of the big HVAC controls mfg. for over 20 yrs. I would suggest you use SilPhos, copper to copper no need for a flux if the copper is cleaned. The discoloration you see may be simply the make up of the solder you are using. If it has a high copper content you WILL have a chocolate looking joint. Silphos will give you a brighter closer to silver looking joint. One other tip if you can find silphos in a small enough diameter you can bend it into a ring and slip the ring onto your joint, slowly heat from the bottom up, and bam you'll have a perfect joint every time...really works well with soft solders 50/50, 95/5.
That's another thought 95/5 soft solder is incredibly strong and can be used in many many low pressure to mid pressure applications.