How To Solder Tips

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 A Coppersmith by trade, these soldering instructions should be helpful to to experts and beginners. Copper and tin solder easily with hot irons, flux and 50/50 solder. You can also get low-lead solder if you so desire.

 I thought I would share some info on soldering here. I dug some old zinc coated tin out of a corner of the shop for the demonstration. The joint is 3/4" deep and I cleated the pieces of metal together. Excess cleat material shows up about every 8" as a dissimilar metal. It won't be there on a roof.

 Talking about flux. Stay-Clean, Ruby, No-Korode and Wet-Oil; ALL leave residue in any voids in a seam, and all of them seep through the rear and bottom of the seams when soldering. No-Korode is the ONLY one that will NOT affect the metal.

These pieces are for illustration only. They are NOT pre-tinned like they will be on actual roof panels.

Before I start soldering, I preheat the joint.

Adding flux only.


Here, the metal is starting tinning with only a bit of flux.


Added Solder.

Notice the Iron is well away from the edge of the metal, and towards the 'rear' of the seam.

Sometimes, the Iron quits drawing, so you add flux right into the solder.

Now, notice I've drawn the iron along the seam. This pulls solder with the iron. You have to keep feeding solder into the joint where the iron had been, NOT where it is. Keep iron away from edge of joint.

To smooth joint and to clean any trash or dust that floats up, us a clean rag, or even a paper towel. I prefer the reusable 'shop towels' similar to paper towels.


How to Solder Copper

For comparison, I also soldered together a couple of loose pieces of copper. The process is the same.


To start, I pre-heated the copper.


The copper is starting to draw the 'tin' from the iron here. I've added some flux.


Now, I'm starting to add solder. Notice the iron is away from the seam edge.


Iron hasn't moved, and the picture doesn't do it justice, but I'm still feeding solder in the same spot. It's starting to show up to the left of the bar.

 Moved the bar to check solder. It's filling the joint nicely.

Moved the iron, and re-applied solder back where I started. I don't want to draw the solder from the beginning of the joint. So, I keep feeding almost 2" from where the iron is. And yes, the bar is still melting in this picture!

. Doesn't appear to be enough.

So I added more solder. Joint is still drawing,

Finished joint. Note the solder all the way to the left.

End view of the piece. Though there is a holiday at rear of joint in place where iron never was, the solder comes all the way through the joint.


Another  view, same shot.

On this last picture, I took a hammer and drove a scratch awl into the joint. Took a couple of hits. Notice the solder is solid on all the layers.

Here's a picture of the same piece, taken from the back of the piece. This is the bottom. The silver line showing in the joint is where the solder came completely through the joint. Also take note of the discoloration of the metal caused by the heat.

Some people don't realize. SOLDER FOLLOWS THE HEAT! IT WILL NOT RUN INT0 A JOINT IF THE IRON IS IN FRONT OF THE SEAM! Try it on a flat piece of copper. A bit of flux, an iron. Somebody let me know how far from the iron it went.

   I almost never solder counter-flashing. By definition, it's not in 'direct water flow', like the roof and doesn't require the same techniques.
When making a repair, I use SS wire brush, and 'Stay Clean' liquid flux. Most times though, I end up replacing the bad area. Remaining thickness of metal will be a huge factor too. If copper comes really clean, Amco Oil, Wet-Oil, or Oatey may work fine. Plan on having a variety nearby.
If it's a flatlock type joint, I clean areas, (3" wide), on both sides of the joint thoroughly, then cut the existing joint out. Form new flatlock piece, I side bent 160 degree, other side 90 degrees, hooking hardest side first, then 'tuck' the 90 degree side under. Allow 1/4" play or you'll be working against yourself.

If the metal is green, it might not work at all. Sometimes, what works on a section of copper, might not work 10' away on same piece. Lot of 'ifs' here.
FWIW- I will only work T&M for this type repair.


Real World Project

Here's some pics of current project. I had NO input here. This was built and gutters made before I started. This is a Rent-A-Roofer project. The copper was a bit tarnished before I started. No-Korode didn't like it. I switched to WetOil.

First 3 pics are of me preheating the seam, then, after I've removed the solder bar, the liquid solder is following the iron across. Notice the 1/4" on the lower piece? That's where it was pre-tinned, and the bleed out. Wish my vertical seams were that smooth.


Awfully skinny gutter! I had to bend a new iron to solder this stuff.


Next pics are of me heating and trying to sweat a vertical seam. Notice the iron location. Solder draws upwards better than down! As the seam fills and starts to leak out, I ease the iron upwards and the solder follows it.


The verticals on the corners are double-locked, and fully sweated. Mighty tarnished gutter! WetOil splatter didn't help it any either. I don't fully smooth my seams after sweating. Just too much chance of popping the seam, IMHO.  I just get the rough edges off. It will all smooth out as it weathers. A good soldered joint will last as long as the copper. 20-60 years, easily, dependant on factors like acid rain, etc.


Below, I've displayed a series of soldered copper pictures that are of a window well I did about 14 years ago. Little solder outside the joints. The soldered joints are still solid as a rock, as the saying goes.


 Here are close-ups of those same seams. There is very little solder in front of the seam. There is a lot of solder on top of the seams. That's where the iron rode and how it drew the solder into the rear of the seam. A seam with little or no solder on top is useless.


Below, I've posted some pictures of soldered seams believed to be 7-8 years old. They are all leaking. All the solder was deposited on the leading edges of the seams. None drawn into the seam. Not sweated, as it should have been. Result? A roof that should have been good for 100 years is already shot. Should just used 'roll roofing' material as far as I'm concerned. It might have lasted 7-8 years, and only cost 1/100 as much.


A real world example of sweating the front of a seam, instead of the back of it. Not even a flat-lock, but the solder didn't flow.

See the crack? Notice the track from the iron is on the 'inside' piece, which means it's outside the joint area? The track should have been on the other piece to draw the solder inside the joint. Here's the joint. Notice the lack of solder inside the joint? What solder leaked into the joint did not bond the pieces together. The iron must be place where you want the solder to end up! Not on the edge of whatever you're sweating.

I went onto a roof I did with Terne Tin in 1988. Here are a couple of the seams I soldered then. The pictures were taken 6-28-2011.

    As you can see, the paint is peeling and there is some rust from lack of maintenance.  Please note there are no cracks along the seams indicative of failure.

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