​Troubleshooting Soldering Problems

​Troubleshooting Soldering Problems

Posted by BarlowsGems on 23rd Apr 2024

Previously I posted a blog about mastering basic soldering skills, you can find it here:

Last month we talked about some problems that arise when learning how to cast.  You you find that blog here.

This month we will discuss some common problems when learning how to solder and how to fix them:

Solder won’t flow

  • 1.  Surface of the metal was not properly cleaned.
  • 2.  Using too small a torch tip.
  • 3.  Not enough heat was applied to the metal. Remember you must heat the metal on both sides of the joint, up to solder flow temperature. If you heat one side more than the other, the solder will flow to the hot side.
  • 4.  The heat was applied to the wrong spot on the metal.
  • 5.  Too much flux used on joint.

Solder flows where you don’t want it

  • 1.  Solder will not flow in areas of metal painted with yellow ocher paste, india ink, or any commercial anti-flux mixture.
  • 2.  Drawing an outline with a #1 graphite also prevents solder flow.

Solder balls up

  • 1.  Too much heat applied to solder. You do not need to directly heat the solder, it is one of the smallest pieces of metal and will melt first.
  • 2.  Not enough heat applied to the area around the joint to be soldered.
  • 3.  Too little solder was used.

Solder runs away from joint

  • 1.  The heating of the metal around the soldering joint was not even -solder will flow towards the source of the heat.
  • 2.  Surface of the metal was not properly cleaned.
  • 3.  Not using enough flux.
  • 4.  Using too large a torch tip.
  • 5.  Too much heat coming from the torch tip.

Gaps in the joint

  • 1.  Surface of the metal was not properly cleaned.
  • 2.  Dirty solder.
  • 3  .Parts didn’t fit correctly.

Solder flows unevenly over metal surface

  • 1.  Surface of the metal was not properly cleaned.


In metals with copper, including sterling silver, the copper can oxidize causing a scaly stain known as firescale.

  • 1.  Prevent firescale by dipping the metal piece into a solution of powdered boric acid 15g and methyl alcohol 50 ml, prior to soldering. You can also buy a firescale prevention solution.
  • 2.  It’s best to heat copper metals quickly. Avoid overheating.

NOTE- Firescale is very difficult to remove, you can try sanding it away, but it is much better to take precaution to prevent it.

Pits in solder seam

  • 1.  Surface of the metal was not properly cleaned.
  • 2.  The solder was not clean.
  • 3.  Too much heat was applied for too long to the solder joint.
  • 4.  Repeated heating of the solder joint in soldering multiple times, which can result in decomposition of alloys in the solder.

Pits when using gold solder

Gold solder does react differently than silver solder. The temperature range when working with gold solder is much lower that with silver solder. If you apply heat for too long to gold solder, small pits will appear in on the metal sheet along the solder seam.

  • 1.  When using gold solder, heat the item to be joined as quickly as possible and release the heat immediately upon completion of the solder flow.

As you can see, it is very important to make sure the solder, flux and metal surfaces are clean. Dirty surfaces can cause a lot of the above problems. First scrub your hands using soap. Clean both metal and solder with steel wool and remove any finger print oils with denatured alcohol. You can pull your wire solder through a green scrubby a few times.

Using flux and keeping it uncontaminated is very important too. Pour your flux into a very small container (such as a jar lid) each time you use it and throw away the unused portion. Use decent brushes for flux made of fur or hair and replace as needed. Bamboo brushes work great or you can buy actual flux brushes. There are many different types of fluxes. Make sure your Flux is designed to use with the metal being used. Flux is a great indicator of the right amount of heat. The flux will get translucent near solder flow temperatures.

The size torch tip you use is also important. Unfortunately, sometimes it is just a matter of practicing to find which size tips work for you. Here is a helpful tip, start with 3 tips-a small, medium, and large. The large tip is used for annealing, steelwork, refining, and for soldering large pieces. The small tip is for tiny solder joints. For everything in between, use the medium tip.

Check back in the next few months and I will delve deeper into more soldering techniques!