Silver solder flux has dried out.

This is the silver solder flux I use for soldering copper and brass.

silverBrazing Flux 602 (nationalwelding.com.au)

I have not done any model engineering for a while as I have been too busy with full time work but now we have all been stood down from the hotel until further notice due to lack of business caused by Australia wide lock downs.

The flux paste has dried out a bit ; it is more a thick cream than its usual liquid form. Can I just add a bit of water and keep on using it or should I ditch it ?

Since the datasheet that you link to says the flux is a water mixture, I'd say that adding a bit more won't do any harm

I don't have your exact brand of flux, but the "Lucas Milhaupt" brand stuff I have has dried out and been re-wet several times and works fine. Take a small lump of your flux and wet it, do a test joint on something non-critical to be sure.

If you have a large lump of hard flux, grinding it down using a mortar and pestle will make it easier to make back into paste with water.

Mixing the dried out flux with water has worked well. Here is my latest boiler. Note that the chimney is only cosmetic and it is not open to the firebox as this results in too much heat loss. I thought the boiler looks a bit strange with no chimney. The other hole in the top is for a Mamod safety valve.

Edited By Brian John on 11/09/2021 14:24:30

I personally don’t like water mixed flux as when heated the water boils off spreading the flux over the job, I mix mine with meths and when this is heated the flux dries in its original shape, very important on small jobs because the sil sol does not spread over the job in hand = neater job = less solder used= less money spent. I have to say that The last bit is a bit of Kieth Hale.

This brand of flux I use is one of the most popular in Australia. I had never heard of meths based flux. Doesn't it burst into flame when it is heated ?

Meths does not ‘burst into flames’. It burns off only after evaporating. Small amounts of vapour will burn with a colourless flame. Alcohol explosions only occur with higher alcohol vapour concentrations in the atmosphere. Stupid people converting fat/oil to biodiesel, or distilling alcohol, in an enclosed space are typical instances of destruction of garages and homes. Particularly when using non-spark -proof kit for the job.

Anyone who has ever used a meths burner or paraffin heater would likely understand how it works.

Thanks ndiy