# Blue crystals on ugly silver bar?!



## Owltech (Apr 25, 2018)

Parted silver, reduced with sodium formate
the crystals remind me of the ones you get on galvanised steel


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## 4metals (Apr 25, 2018)

Blue? I see a tan cream colored crust. To me, it looks like a slag of melted silver chloride. Silver chloride melts long before the silver but doesn't boil off the molten silver and when you pour your bar it ends up on top just as a slag would. I assume you used a clean crucible and no flux at all.

I think you didn't rinse the remaining silver nitrate out of the formate solution and converted it to chloride when rinsing with tap water. Whatever was retained in the silver metal crystals ended up looking like the tan slag. 

But if that really is blue, I have no idea what it is.


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## Owltech (Apr 26, 2018)

4metals said:


> Blue? I see a tan cream colored crust. To me, it looks like a slag of melted silver chloride. Silver chloride melts long before the silver but doesn't boil off the molten silver and when you pour your bar it ends up on top just as a slag would. I assume you used a clean crucible and no flux at all.
> 
> I think you didn't rinse the remaining silver nitrate out of the formate solution and converted it to chloride when rinsing with tap water. Whatever was retained in the silver metal crystals ended up looking like the tan slag.
> 
> But if that really is blue, I have no idea what it is.


Spot on! Never fired, brand new, SiC crucible, no flux at all... just the stock glaze the crucible comes with:


The silver cement was not bone dry, but just a wee bit moist




the crucible after pouring:




the blue glitter I was talking about:




as for the tan coloured crust (which a pinch of borax should have taken care of), was caused (IMHO) by the crucible''s original glazing, or by the rusty steel mould used to pour the silver into:




I'm excluding the presence of Cl as I've used de-ionised water throughout the whole process. The rinse water was tested for silver nitrate presence with diluted HCl and no cloudiness was observed. Final rinse water pH was 7. And finally, the silver powder remained unchanged after prolonged exposure to sunlight.


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## Yggdrasil (Apr 26, 2018)

Hi! 
Are you sure it is actual coloration or just reflections from crystalline boundries like multi crystalline silicone or as you say, Zinc has. To my eyes, on this picture, that is what strikes me.


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## Owltech (Apr 26, 2018)

Yggdrasil said:


> Hi!
> Are you sure it is actual coloration or just reflections from crystalline boundries like multi crystalline silicone or as you say, Zinc has. To my eyes, on this picture, that is what strikes me.



the glitter occurs when the silver bar is placed at a certain angle to the light


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## Yggdrasil (Apr 26, 2018)

Ok. 
Then it is some kind of reflection or frequency modulation of the light at crystal boundries. But to what causes it or why. I think we are on the correct place to get an answere


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## cuchugold (Apr 27, 2018)

Nice pics. Did you follow the exact procedure initially posted by 4metals for the formate reduction or added/changed something?. With a graphite ingot mold, your bar appearance would be much better.


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## Owltech (Apr 27, 2018)

cuchugold said:


> Nice pics. Did you follow the exact procedure initially posted by 4metals for the formate reduction or added/changed something?. With a graphite ingot mold, your bar appearance would be much better.



I followed patent US5000928A by Kodak Co (very similar to the procedure laid out by 4metals) with small changes,

Following your advice, I re-melted the bar and poured the silver into a graphite mould and this is the result: (please note that the tan coloured crust and the "blue glitter" remained even after addition of borax)




the bar (in the middle) compared to two other bars refined by cupellation (the surface on all bars is smooth despite appearing rough)


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## cuchugold (Apr 27, 2018)

I'm not really sure about the colors. Perhaps some Pd oxide or even Pt contamination?. 4metals or Lou will probably know better. It usually pays to scavenge with DMG in those Pd++ and Pt++ nitrate solutions, before reduction of silver. Very cool pics. Thanks for posting.


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## Owltech (Apr 27, 2018)

cuchugold said:


> I'm not really sure about the colors. Perhaps some Pd oxide or even Pt contamination?. 4metals or Lou will probably know better. It usually pays to scavenge with DMG in those Pd++ and Pt++ nitrate solutions, before reduction of silver. Very cool pics. Thanks for posting.



Thank you, DMG was the "small change" prior sodium formate addition


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## cuchugold (Apr 27, 2018)

When highest purity is required, evaporation to crystals, and then fusion of the crystals in a furnace at above 250 C and less than 444 C (If I remember correctly) is what is required to make oxides of all contaminants. After cooling, dissolving in distilled water, the oxides can be filtered out, and then go for formate reduction. Really fine silver can be obtained, with 2 iterations, 999995 for sure. :G


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## Palladium (Apr 27, 2018)

The blue crystals show up in high purity silver and appear as holographic crystals. 
Their is something else going on here with that other layer. What was the source materials?
Formate will reduce platinum and palladium if you don't control the ph and the temp.
Try dropping the silver first and then going after the pd or pt if you suspect that. DMG before the drop may be your problem. Lou and 4metals are the best when it comes to these problems!
Try washing a sample of the powder in hcl and then melting it and using graphite.


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## goldsilverpro (Apr 27, 2018)

I'm with Palladium. That silver bar looks pretty pure to me. I've had those bluish crystals many times on silver I knew was pure.


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## Owltech (Apr 28, 2018)

Thank you all for helping me out! Starting material was the nitrate solutions of these:
(dore on the left, the recovered metal on the right)



After raising the nitrate solution's pH to 6 with KOH:


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## cuchugold (Apr 28, 2018)

If GSP tells you that your silver is good, that's as good as mint stamp. 

Now for the tan colored crust: Maybe you can fix that by adjusting your pouring technique. In minute 1:04 of the video below, you will see someone slagging the pour of an already refined gold bar, to make the surface better. Try to hold the 'floating stuff' inside the crucible with a ceramic or graphite rod, and your bar will be smoother. Great pics!.

https://www.youtube.com/watch?v=nQ37SFKahc0


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## Owltech (Apr 28, 2018)

Thank you for the reassurance you have given me! Nice video btw


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## Lou (Jun 4, 2018)

Yes, the crystals are what you get when the silver is pure.

Bigger the crystals, the purer the silver. Gold does same thing but less iridescent.


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