flux question

[gilessim]

Does flux go off?, I've just been trying to silver solder something with good quality silver solder that I bought a while ago, using some flux given to me by a silversmith that I've used before with good results but now (it's powder) it seems to have become humid and a bit gummy and anyway doesn't seem to work and doesn't burn away,it leaves a white residue, I cleaned the bits very carefully and also used an acid from the same place I got the solder but it just won't flow!,I always used the flux before making a paste with a little water and it worked fine ??? I don't know what's going on!

any thoughts?

Giles

 

[Kermit]

The acid could have evaporated. Sulfuric doesn't evaporate, but Hydrochloric acid does, and I don't think any of the flux I've used has ever contained sulfuric acid.

If its useless as it is, you might try adding some muriatic acid(hydrochloric), just a few drops to lower the pH.



It's a thought,
Kermit

 

[Kermit]

WRONG.

Well, some of my answer was, but not all.


Check this for MO BETTER information.

http://www.cupalloys.co.uk/fluxes-c59.html

 

[rickharris]

Does the flux powder melt and form a glassy like surface? If so it is a borax based flux and shouldn't go off. It is hygroscopic and so will absorbe water from the atmosphire theough this should not spoil it.

If it is a powered acid - Then it may have become contaminated and inactivated.

Personally I prefer Borax for silver soldering. I tend to use a borax cone as they keep forever!

 

[Alan J. Richer]

+ 1 on the borax. If you insist on anhydrous borax (usually used when forge welding per an old blacksmith friend of mine) just get the plain old 20 Mule Team stuff from the grocery store and spread it on a cookie sheet, then bake for an hour (preferably when SWMBO is out of the house). Toss that into a paint can with a compression lid and it will keep for a good long time.

If you are doing very fine work a mortar and pestle or the yard sale equivalent (a cheap coffee grinder) can be used to make fine particles.

Personally, I just mix it with a bit of alcohol and go with it - flashes off nice, doesn't leave a whole lot of water-based crud (from the mixing water - got hard water here) and generallly just work great.

Alan

 

[gilessim]

Thanks for the replies guys! and great link Kermit!, I still don't know what type of flux mine is but it definitely doesn't seem to melt any more! for me it's gone off so I'm off to find some borax based stuff!

Giles