Soldering Bubbles

While doing a simple band repair I had to grind some solder off because I put too much on the break. In removing the solder I noticed that some “bubbles” were exposed within the solder. Can anyone explain how I could avoid getting bubbled within the solder?
My thinking is that the torch flame might be too hot causing the flux to buble.

I am interested in the answers that you get to this question as I too have the same thing happen from time to time. The explanations that I have heard include: zinc in the solder vaporizing, something about the flux, the solder cooled too quickly, dirt, etc. Since it is solder, I can usually remove the problem by removing the solder, but sometimes I need the solder to stay where it is. It can be moved around and smoothed a bit with a rotary hammer. I look forward to what others have to say. Thanks…Rob

Hello all
It’s not the flux, that’s boiling of the solder, and the bubbles are gas porosity. The zinc, and or cadmium, is vaporizing and the gas is being trapped in the solder.

I would suggest to avoid overheating the solder by using indirect heat. That is, heat the ring not the solder. Let the ring transfer the heat to the solder.

Hi Rob, Ted here,
How you join depends on the work. Re the original poster was to join a wedding band?
then ,

  1. they should use a snippet of foil placed in the joint. not on the outside.
  2. they should use a reactive flux, well covering the joint area applied as a powder of a titanium wire.
    borax has been surpassed many yrs ago.
    3.they should use a flame of the right size, slightly reducing past neutral
  3. they should use a spring loaded holding clamp that applies closing pressure to the band as the solder melts.
    In your scenario, you dont mention the work, material ,joint type etc so cant really give a professional tech answer.
    Its usually a combination of tech faults that give faulty joints.
    I join many things which have to be forged and/or bent after joining so my joins have to be 110% every time otherwise they just come apart!!.
    One example is a round bangle, this is made from 5 wires,2 cu/tin bronze., 1 10% ali bronze and 2 ni chrom so im butt joining a total of 10 wires.
    They have to be all flat and touching with foil in the joint.
    The flux is a 50/50 mix of Johnson Matthey s/steel grade easyflo and ali bronze easyflo.
    Brazing foil is easyflo 50% silver/cad.
    flame is a soft oxy propane 1/2in dia . Works perfectly with the spring clamp every time.
    will accept aggresive hammer truing up.
    Hope this helps.
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I was repairing a cast sterling silver band on a Puzzle Ring. I cleaned the area of the joint with a file and used “Ultra Flux” as I usually do.
I used a hard solder wire and the flame melted the solder and created a ball which then attacked to the broken band.
When I ground the solder repair down is when the voids were revealed. (I am a little out of practice with my soldering technique.)

This insight seems valid to me, I will try the indirect heating on my next repair. I will pray that I don’t melt the band before the solder melts.
I was repairing a cast sterling silver band on a Puzzle Ring. I cleaned the area of the joint with a file and used “Ultra Flux” as I usually do. I used a hard solder wire which balled up before it melted on the band.
What hardness of solder do you suggest for this type of repair?

HI Joseph
Keep in mind you could use a medium silver solder if you think it would melt your pc when using hard. Regardless it shouldn’t melt the pc.

David H. Fell & Co.

Thanks @DHFCO!

Joseph- I usually wait until the ring is near soldering temp. before I add
my solder. The less time you spend heating the solder the less likely that
you will burn it thus causing pits. I use a good paste flux like Handy
flux. When the flux is heated til it melts into a clearish liquid then I
know it’s time to add my solder pallion.
Also the more often you reheat solder the higher the melting temp. If your
solder doesn’t flow right after two tries then remove it and use fresh.
When soldering silver which love to sink heat I heat the whole piece with a
softer flame. When it’s ready to solder then i tighten up my flame a little
hotter and only then do I concentrate my flame on the joint. If a piece
doesn’t solder right in less than a minute it’s time to stop and evaluate
what is going wrong.
Have fun and make lots pf jewelry.
-Jo Haemer


The answer is already given by @DHFCO mentioning zinc as the perpetrator.

Low melting solder is more a trouble maker then hard solder due to the amount of zinc in the solder as DHFCO already mentioned.

This phenomenon is called “zinkfras” in the German language caused by too high solder temperature.
Zinc starts to boil creating the little bubbles.

Remedy? Remove the bad part and use hard solder.

Soldering is a procedure of temperature control and recognition when to step in with the solder preventing the boiling of your solder or better the zinc used in your solder. Working with solder is knowing what you’re doing and how the metals behave in a alloy. It’s not rocket science but common sense and practice.