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Scrap Silver Thread

PostPosted: Sun Dec 12, 2010 12:07 pm
by triple-agent
OK - some background

I have been recently selling a lot of odd bits of silver i have collected over the years - things like forks, spoons, watch cases, ash-trays etc. that i have got from car boot sales, auctions etc.

The recent relative high pos has tempted me to offload some of this 'scrap'. Interestingly, some of it I was actually selling as antique/collectable, such as spoon sets with C19th. hallmarks etc. in excellent condition; however, this stuff was all bought by someone for the sole purpose of melting down! What does that tell you? (collect antique silver items maybe!!!)

Anyway, I have been tempted to have a go at melting .925 myself with a view to producing .925 bars: It doesn't matter to me that they will have no assay marks, because as far as i am concerned there are easy enough ways to determine (roughly) silver content especially with colourmetric acids. Also, when (if) I do come to sell, I appreciate that there will be a 'mark-down' of sorts.

So, where am i with this? well, I have done some research on melting and pouring (see http://chestofbooks.com/crafts/mechanics/Cyclopaedia/Melting-Silver-In-An-Open-Fire.html)

This section is from the book "Cassell's Cyclopaedia Of Mechanics", by Paul N. Hasluck. Also available from Amazon: Cassell's Cyclopaedia Of Mechanics.
Melting Silver In An Open Fire

Procure a small fireclay crucible in which to melt the silver. For a flux use equal quantities of finely powdered charcoal and sal-ammoniac. Make up a large, bright coal fire in an open grate, and when the fire is quite clear break a, hollow space in the centre. In this space place the crucible, and allow it to get red hot; then put in the silver, and draw some of the hot coals closely around and over it. Blow the fire with the bellows until the crucible gets white hot, when the silver will melt, the fusing point being at 1873° P. (1022-7° C). Then add the flux to clear the surface from scum. Again make the crucible hot, and quickly pour the contents into an iron ingot mould previously made scalding hot. One or two ounces of silver may be melted at a time in this way. The flux may be stirred with a pointed rod of iron previously made red hot.


I have already bought a crucible, cast, and tongs, and i am currently researching a suitable flux.

Image

I have a good size open fire with a large cast iron grate which i will be burning coal (doubles) in and i am able to blow air under the grate (please note - I have no draft system on this so - it is pretty open all the way up to the chimney stack)

I will let you know how i get on and am welcome to tip, suggestions etc. esp. wrt a suitable lux

Re: Scrap Silver Thread

PostPosted: Sun Dec 12, 2010 1:40 pm
by smeagol
I'd be really interested in how you get on with this. thx

Re: Scrap Silver Thread

PostPosted: Mon Dec 13, 2010 11:41 pm
by triple-agent
i am a little nearer to going ahead with this - the one thing i am stalling on is an appropriate flux and using it correctly.

Flux can be boric acid or a borax/boric acid mix. Use it as a dry powder, sprinkled onto the metal. Do not try to use a water based flux since steam is a direct consequence. If you want to coat the metal with a bit of flux before beginning to heat for melting, put some boric acid in denatured alcohol, stir well and brush on the metal. The alcohol will evaporate or burn away (either is ok) and a fine powder then coats the metal. Heat to melt and along the way add a pinch of the flux sprinkled on while melting.

For the crucible to be first lined with boric acid is a good idea but not essential. This will protect the crucible as much as anything and help prevent crucible flakes from getting into the metal. To do this, heat the crucible to red and sprinkle on boric acid powder as needed while turning the crucible at various angles to allow the melted powder to coat the surface.

Generally, once cooled, if the ingot form does not have any undercuts, a tap or two will release the metal ingot. If it sticks, this may be from flux which hardens like glass. A boil in water will remove the flux. If it does stick and will not release, you may loose the ingot mold in the process of removal.


http://en.allexperts.com/q/Jewelry-Gems ... Silver.htm

I can get boric acid and borax on ebay, so basically the procurement of the flux is sorted.

this vid definitely shows the flux being added at the melting stage

[youtube]iHpm2crMwGY[/youtube]

edit - and here...

[youtube]dMKhldrpmXU[/youtube]

Re: Scrap Silver Thread

PostPosted: Tue Dec 14, 2010 7:58 am
by smeagol
Once you made the ingots Triple A what will you do with them? are you going to try and turn .925 into .999 through electrolysis?

Re: Scrap Silver Thread

PostPosted: Tue Dec 14, 2010 8:46 am
by triple-agent
smeagol wrote:Once you made the ingots Triple A what will you do with them? are you going to try and turn .925 into .999 through electrolysis?


hello smeagol

i think i will stick with .925, i am happy to have chunky sterling ingots as the end product - though there could be some repeat runs in trying to get the pour done right. having watched some vids, this seems to be the most crucial part, esp. eliminating air pockets and making sure the right amount of flux is used. i will probably be quenching the bars quite soon after pouring.

got the borax and boric acid ordered last night so hopefully will have my first run at this before xmas :thumbup:

Re: Scrap Silver Thread

PostPosted: Tue Dec 14, 2010 10:06 pm
by Ziknik
triple-agent wrote:...
got the borax and boric acid ordered last night so hopefully will have my first run at this before xmas :thumbup:

Dam, I'm too late to make a recommendation... but I've been to Biostain and they are a very professional chemical vendor. I had a good look round the warehouse, the way they store and package is top quality.

http://myworld.ebay.co.uk/biostain-on-e-bay/

Re: Scrap Silver Thread

PostPosted: Tue Dec 21, 2010 5:24 pm
by triple-agent
Ziknik wrote:
triple-agent wrote:...
got the borax and boric acid ordered last night so hopefully will have my first run at this before xmas :thumbup:

Dam, I'm too late to make a recommendation... but I've been to Biostain and they are a very professional chemical vendor. I had a good look round the warehouse, the way they store and package is top quality.

http://myworld.ebay.co.uk/biostain-on-e-bay/


thanks zik - i go the boric acid and borax today, so tonight i will have my first stab at this :?

Re: Scrap Silver Thread

PostPosted: Tue Dec 21, 2010 8:23 pm
by Pixel8r
triple-agent wrote:thanks zik - i go the boric acid and borax today, so tonight i will have my first stab at this :?

Good luck :thumbup:

Please let us know how it goes.

Re: Scrap Silver Thread

PostPosted: Tue Dec 21, 2010 9:56 pm
by triple-agent
quick update (as i have another melt on the go here)

this was easier than i thought! the silver melted a treat, i probably used to much flux on the final pour (I have definitely added too much on the 2nd melt so far!) but i am please with the result, i may just file down the scummy exposed (pour) side. Next time i do this i am going to use less flux and try and not contaminate the mix unless oxidisation (catches fire) occurs.

Image

Image

i will post a pic of the scummy side later!

Re: Scrap Silver Thread

PostPosted: Tue Dec 21, 2010 9:57 pm
by triple-agent
scummy side

Image

Re: Scrap Silver Thread

PostPosted: Wed Dec 22, 2010 10:47 am
by fwiw
triple-agent wrote:quick update (as i have another melt on the go here)

this was easier than i thought! the silver melted a treat, i probably used to much flux on the final pour (I have definitely added too much on the 2nd melt so far!) but i am please with the result, i may just file down the scummy exposed (pour) side. Next time i do this i am going to use less flux and try and not contaminate the mix unless oxidisation (catches fire) occurs.

Image

Image

i will post a pic of the scummy side later!


TA - that looks beautiful! You should get a custom mould made with your mint name on it!

Re: Scrap Silver Thread

PostPosted: Wed Dec 22, 2010 4:48 pm
by triple-agent
fwiw wrote:
TA - that looks beautiful! You should get a custom mould made with your mint name on it!


thanks!

ha - the mint mark would be pretty cool.

i have some more scrap to melt so maybe i will try this next time - though quite how i am going to do this is beyond me; i guess i would need to file / grind an insignia out of iron first?

Re: Scrap Silver Thread

PostPosted: Wed Dec 22, 2010 6:16 pm
by fwiw
triple-agent wrote:
fwiw wrote:
TA - that looks beautiful! You should get a custom mould made with your mint name on it!


thanks!

ha - the mint mark would be pretty cool.

i have some more scrap to melt so maybe i will try this next time - though quite how i am going to do this is beyond me; i guess i would need to file / grind an insignia out of iron first?


I bet pix could do a really cool Stencil for you to use an engraver on!

Although, I am not sure myself how you could do it as it might take long time!

Re: Scrap Silver Thread

PostPosted: Wed Dec 22, 2010 6:28 pm
by fexx
triple-agent wrote: the mint mark would be pretty cool.
i have some more scrap to melt so maybe i will try this next time - though quite how i am going to do this is beyond me


How about one of these?

http://cgi.ebay.co.uk/SILVER-CARAT-PUNCH-925-STAMP-YOUR-SCRAP-925-/300401337308?pt=UK_Crafts_JewelleryMaking_GL&hash=item45f150a3dc#ht_1328wt_936

(If it works, I'd have one made with my face on it ;) )

Re: Scrap Silver Thread

PostPosted: Wed Dec 22, 2010 6:38 pm
by fwiw
fexx wrote:
triple-agent wrote: the mint mark would be pretty cool.
i have some more scrap to melt so maybe i will try this next time - though quite how i am going to do this is beyond me


How about one of these?

http://cgi.ebay.co.uk/SILVER-CARAT-PUNCH-925-STAMP-YOUR-SCRAP-925-/300401337308?pt=UK_Crafts_JewelleryMaking_GL&hash=item45f150a3dc#ht_1328wt_936

(If it works, I'd have one made with my face on it ;) )

That would only stamp .925 on the bar!

Re: Scrap Silver Thread

PostPosted: Wed Dec 22, 2010 6:41 pm
by triple-agent
fwiw wrote:
fexx wrote:
triple-agent wrote: the mint mark would be pretty cool.
i have some more scrap to melt so maybe i will try this next time - though quite how i am going to do this is beyond me


How about one of these?

http://cgi.ebay.co.uk/SILVER-CARAT-PUNCH-925-STAMP-YOUR-SCRAP-925-/300401337308?pt=UK_Crafts_JewelleryMaking_GL&hash=item45f150a3dc#ht_1328wt_936

(If it works, I'd have one made with my face on it ;) )

That would only stamp .925 on the bar!


it's amazing what you can get on ebay - i hadn't even considered this!

there is a full set of letters here

http://cgi.ebay.co.uk/RDGTOOLS-LETTER-S ... 439d488fcc

Re: Scrap Silver Thread

PostPosted: Thu Dec 23, 2010 10:04 am
by Ziknik
triple-agent wrote:it's amazing what you can get on ebay - i hadn't even considered this!

there is a full set of letters here

http://cgi.ebay.co.uk/RDGTOOLS-LETTER-S ... 439d488fcc


http://www.toolstation.com/shop/Hand+To ... 190/p19757

Re: Scrap Silver Thread

PostPosted: Thu Dec 23, 2010 10:10 am
by Ziknik
TA,

I think you might get a better finish if you vibrate your mould during/after pouring.

You will need a variable speed sex toy for this. Use it to vibrate the stand where your mould is sitting. I am not joking btw.

Concrete vibrators consolidate freshly poured concrete so that trapped air and excess water are released and the concrete settles firmly in place in the formwork. Improper consolidation of concrete can cause product defects, compromise the concrete strength, and produce surface blemishes such as bug holes and honeycombing. An internal concrete vibrator is a steel cylinder about the size of the handle of a baseball bat, with a hose or electrical cord attached to one end. The vibrator head is immersed in the wet concrete.

External concrete vibrators attach, via a bracket or clamp system, to the concrete forms. There are a wide variety of external concrete vibrators available and some vibrator manufacturers have bracket or clamp systems designed to fit the major brands of concrete forms. External concrete vibrators are available in hydraulic, pneumatic or electric power

Re: Scrap Silver Thread

PostPosted: Thu Dec 23, 2010 10:12 am
by Ziknik

Re: Scrap Silver Thread

PostPosted: Thu Dec 23, 2010 11:25 am
by fexx
Ziknik wrote:You will need a variable speed sex toy for this.


You'll need a big one - you are f**king JP Morgan, after all.
:D