This isn’t very scientific, but I may repeat and/or expand this test. All examples given here were done with small sterling silver rings and Cookson’s easy silver solder wire, using a small oxy-hydrogen flame. The solder is cadmium free. Each example has the material in BOLD, followed by a description of the effect.
Having tested more materials, I am concerned about variation in my materials and method – for those materials that seem to be effective, I’ll eventually try testing them under more controlled conditions.
NO FLUX – Very poor result. Metal was partially melted before the solder ran through, and only 50% of the join was filled.
AUFLUX – Very good result. Light glass residue.
BORAX POWDER – Good result. Heavy glass residue.
BORAX + WATER PASTE – Good result. Less glass residue due to more precise placing of paste.
BORAX + BEESWAX – Good result (surprised me), only slight residue of glass due to low quantity of borax.
BORIC ACID POWDER – Very good result. Heavy glass residue. Definite red/orange colour to the glass with all boric acid tests.
BORIC ACID + WATER PASTE – Average result. Heavy glass residue. Slight surface melting on the silver, but that may be my error.
BORIC ACID + BEESWAX – Good Result. Light glass residue.
BEESWAX – Poor result, but much better than using no flux at all. Join was poor, but metal didn’t melt.
SHELLAC (FLAKE/POWDER/+WATER/+BEESWAX) – Very poor in all cases. It was not possible to make a compound with beeswax, and neither was it possible to mix it with water, as it is insoluble. When the water was heated, it yielded a transparent scum, which was collected and tested, but had the same characteristics as the shellac. The silver ring was melted in all cases.
CUTTLEBONE (POWDER/+WATER/+BEESWAX) – Appears to be a potent anti-flux – this is either due to the high calcium carbonate content of cuttlebone, or it might just be that most things work that way – that’s why I want to try dirt, and see if that has the same effect.
CHARCOAL (POWDER/+WATER/+BEESWAX) – Very poor result, usually resulting in a melted ring before solder flowed. As with cuttlebone, this may be acting as an anti-flux, or it may be making the metal surfaces too contaminated. The powder wouldn’t mix with water properly, and left a layer of “skin” on the surface. This seems like an interesting property which might be used to coat objects with charcoal, should it be necessary.
ROSIN (POWDER/+WATER/+BEESWAX) – Very poor result, usually resulting in a melted ring before solder flowed. Rosin, also known as colophony, is used as a flux for lead-based solders, but the temperatures I am using are clearly too high for it, and it burns leaving a dark residue behind.
Summary: I’ve always been told that greasy joins are bad for soldering, so I’m baffled that beeswax doesn’t ruin the work. But, seeing how it improved the effects of borax (ie. less glass residue), it may be worth trying it with other substances, particularly if they are only available in small amounts – barely any borax was needed to get a result. Hopefully I’ll update this post at a later date, with more substances.
Things to try:
- Gum tragacanth
- Coke dust
- Table salt
- Dirt (depends on the dirt, though…)
- Charcoal Ash – this was difficult to produce at the bench, so I’ll wait until I’ve got my furnace ready.
- Cream of Tartar