Using Flux

[TangerineDreams]

Hi,

Do you have to use flux for annealing silver? I have just got a tumbler for polishing my silver, I know that the silver has to be pickled before tumbling but apparently I also have to clean off oxides too. I was told that oxides are formed when flux hasn't been used. I use flux when soldering but I'm not sure if it should be used whenever the silver is heated? As my tumbler is brand new I don't want to do the wrong thing with it!

Thanks
Antonia

This is the flux I use:

http://www.cooksongold.com/Jewellery...ct-description

[sonia]

Hi Antonia

You don't use flux when annealing silver. One useful tip I learned was to use a permanent marker on the silver. Anneal the silver by moving the torch over it - you don't want to use the very tip of the blue cone - that will be too hot. when the permanent marker has disappeared your silver will be annealed and can then be pickled as necessary.

Hope this helps

Sonia
x

[Dennis]

None of this will affect your tumbler, but a great advantage of using flux when annealing is that it helps avoid the build up of fire scale. Any flux applied evenly to warmed metal will do, but some of us use boric acid in meths, painted on with a brush (A saturated solution: keep the bottle away from flame).

It is worth washing your work well before tumbling, to keep you medium as clean as possible.

Sonia's tip about using a marker is valuable too, because it is bad to overheat your metal. Dennis.

[ps_bond]

Recently I've been inclined to use a firecoat when annealling too; currently swapping between Argotect & Magic Boric. Not entirely sure about the Magic Boric yet - not convinced I'm getting enough of coating whereas the Argotect is more obvious.

The marker trick doesn't work if you use a firecoat that involves alcohol BTW...

[Dennis]

Earlier in the year I made some test pieces to compare the effect of boracic acid in meths and Magic Boric. I'm afraid Magic Boric came a poor second for preventing firescale. Tested as a flux it did not perform reliably either. In fax it seems to owe its commercial success entirely to its name.

Recently I have been using up Walshes Fast Flux soldering solution for firescale reduction. It seems to do that quite well, but is no great shakes as a soldering flux. It's turning me into a bit of an alcohol sniffer and would be hazardous near an open flame. Dennis

[lilacmonkey]

All very interesting.liking the results of your experimenting Dennis.
Fire-scale(fire-stain)is one of my bugbears.
must try different things out for myself to see what works.
Stu.

[ps_bond]

Funnily enough, I was having some gyp soldering some gold bezels earlier today (using Magic Boric). Switched back to Auflux and the solder flowed with no problems, entirely predictable again... Pripps is a nuisance to apply (atomiser onto warm metal - lots of overspray); Argotect and boric acid in alcohol are entertainingly flammable. The solution (!) is lots of heat, applied quickly to avoid the firestain forming.

Actually, here's a thought: Depletion gilding of silver (for reticulation) - can it take place at all if you use a firestain preventative? I've just been doing some and while the reticulation isn't as spectacular as some pieces I've done, it is there; I didn't use any Magic Boric in annealing.

[Tabby66]

Definately auflux all the way........soldering, annealing.....gold or silver

(in fact I have an amost full bottle of old Boris, I found it's coverage very patchy.............and I do use boric in alcohol with good results and great flammable entertainment (!!), the pripps was great for coverage but sprayer kept blocking

[Dennis]

You know all this Peter, so just to clarify it in my own mind:

Depletion gilding occurs when on heating, pure silver rises to the surface of sterling silver, so hiding the firescale (copper oxide) beneath it. Flux might still prevent the formation of silver oxide, which is also dark grey but as far as I know this dissolves in pickle anyhow.

Reticulation occurs when a skin of cooled fine silver covers molten alloy solidifying beneath it.

Conclusion: There is probably no place for flux in this process. Dennis.

[ps_bond]

Sorry for the delay Dennis - I've been making sure I got my facts right first!

Depletion gilding/depletion silvering involves oxidising the copper content of the top surface of the silver. Pickling removes the oxide from the top surface. Oxygen can penetrate the alloy when it is at heat; pickle, obviously, can only act on the outer surface. Repeated annealing depletes the copper content further to leave a very thin skin of pure silver once it has been pickled clean. All according to Brepohl.

Here's the bit I still haven't found an adequate reference for, so is my understanding: The sub-surface copper oxide (aka firestain, but deliberate this time!) has a different rate of expansion/cooling than the fine silver, so heating the thin skin of silver (+ some or all of the oxide) to molten results in random movement of the surface as the 2 dissimilar metal/metal compounds cool. What I haven't found yet is whether the movement is purely down to the surface silver, or it is the oxide layer that moves and the silver coats it.

If anyone has a better reference to work to that'd be good - something with photomicrographs better yet!

BTW - the description of reticulation in Anastasia Young's book is wrong.