soldering a rib and pipes

[eddillon]

I am about to solder an under rib to a round barrel and solder the pipes to the rib.  My plan is to rib and pipes at the same time holding everything in place with iron wire.  Before I tin everything, I would like to put something on the areas that I don't want the solder.  At one time I had a stick of something that was like hard chalk for this purpose.  I can't find it.  Any suggestions for the soldering and for a material to protect from running solder?   

[D. Taylor Sapergia]

Soapstone:  welder's marking pencil.

[eddillon]

Bingo Taylor!  Thanks.  Now for some soldering guidance.
Ed

[jerrywh]

I use swiff 95 paste solder. It is hard to find but any good 430° past solder will work just fine.
With paste solder there is no need to tin before hand. cleam all surfaces real well and sand with fine wet and dry paper. 
First I prepare the rib where the rr thimbles go and solder them to the rib. I keep them straight by placing a aluminum rod through them and wiring the rod down to hold them in place while I solder. The rib will not warp at the temps required for that operation.
  I know what some are thinking but for those who may not know here is a little info on soldering.   The first time you melt 430° solder it will melt and flow at about 430° but that changes the alloy. The second  time you heat the same solder it will not melt of flow till about 600°. That phenomena is helpful.
  Now apply the paste solder to the barrel and the rib and wire it in place keeping the aluminum rod and the rr thimbles in place as they were. After it is in place you can wipe the excess solder off with a rag where you don't want it.  Any place you don't want the solder to gat on just paint it with milk of magnesia. Or sodium silicate, Than heat the barrel from the other side slowly until the past melts. The barrel won't warp unless you get it red hot. Sometimes I will put a small spot of the past solder on some place just so I can see when it melts. When it melts you can just wipe it right off with a dry rag. Let it cool naturally.

[bgf]

I had to put a rib on a heavy 11/8 barrel, and it helped to put it on a gas grill, then the torch could make the solder flow relatively easily.  Not saying it was a good thing to do, but it made it a lot easier.

[James Rogers]

I use swiff 95 paste solder. It is hard to find but any good 430° past solder will work just fine.
With paste solder there is no need to tin before hand. cleam all surfaces real well and sand with fine wet and dry paper.  
First I prepare the rib where the rr thimbles go and solder them to the rib. I keep them straight by placing a aluminum rod through them and wiring the rod down to hold them in place while I solder. The rib will not warp at the temps required for that operation.
  I know what some are thinking but for those who may not know here is a little info on soldering.   The first time you melt 430° solder it will melt and flow at about 430° but that changes the alloy. The second  time you heat the same solder it will not melt of flow till about 600°. That phenomena is helpful.
  Now apply the paste solder to the barrel and the rib and wire it in place keeping the aluminum rod and the rr thimbles in place as they were. After it is in place you can wipe the excess solder off with a rag where you don't want it.  Any place you don't want the solder to gat on just paint it with milk of magnesia. Or sodium silicate, Than heat the barrel from the other side slowly until the past melts. The barrel won't warp unless you get it red hot. Sometimes I will put a small spot of the past solder on some place just so I can see when it melts. When it melts you can just wipe it right off with a dry rag. Let it cool naturally.

Hercules no longer manufactures swif 95. Is there another comparable under a different brand these days?

[hammer]

Graphite, rub along the seam with a soft lead pencil.
I note that London gunmakets do nothing when soldering shotgun top ribs.   They clean up afterwards as a part of finishing the barrels.  Perhaps that ensures the solder completely fills the join leaving no voids for rust to start.

Peter.

[jerrywh]

 Black Swan 95-5 past solder is the same for this purpose.