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Author: Subject: My synthetic rubies are somewhat impure, how to make cleaner ?
metalresearcher
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[*] posted on 19-9-2020 at 10:06
My synthetic rubies are somewhat impure, how to make cleaner ?


Using a DC welder with two carbon rods, some Al2O3 powder and 1/50 of that amount of green Cr2O3 to heat the powder mixture to over 2000 C. That worked quickly , but the cavity in the cell concrete also melted, so it got contaminated. I tried again using on a piece of wood. I thought, wood carbonizes and does not mix with Al2O3. But ruby was barely formed, unlike on cell concrete.

On Nighthawking Light videos I saw he got some small rubies on firebrick.

Did anyone experiment with making ruby ?

Video: https://www.metallab.net/jwplayer/video.php?v=L2NsaXBzL1N5bn...
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mysteriusbhoice
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[*] posted on 19-9-2020 at 20:54


the thing with graphite electrodes is that the plasma itself contains carbon and can cause that to be imbedded in your ruby or mixed in when its molten and touching it but best way to avoid most contamination is to strike the arc and ensure that the rods dont touch the pile of ruby but only the plasma should touch it.

if your arc is too small consider using higher voltage around 36 which makes larger sustained arcs.
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wg48temp9
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[*] posted on 21-9-2020 at 00:23


No I have not experimented making ruby. I have attempted the Verneuil process with sand using an oxy propane welding torch but the fast moving flame pushed most of the sand away before it got to the hot part of the flame.

I am surprised that the carbon arc method used by Nighthawk produced ruby that was sufficiently pure, meaning not sufficiently contaminated with fire brick or carbon to not be fluorescent. Perhaps at 2,000C most of the carbon was oxidized and escaped as CO or CO2.

[Edited on 9/21/2020 by wg48temp9]




i am wg48 but not on my usual pc hence the temp handle.

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mysteriusbhoice
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[*] posted on 21-9-2020 at 01:57


my guess is if you have some sort of flux of KNO3 then your carbon wont be contaminating your ruby since it will vaporize into CO2.
NaClO3 works aswell for this purpose but it maybe a little too reactive.
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[*] posted on 21-9-2020 at 02:08


KNO3 will convert the Cr2O3 to chromate so I can't see that helping.
The best thing I can think of to support your Al2O3 / Cr2O3 mix while melting it is more Al2O3.

I'm actually quite surprised to see that you can get ruby that's good enough to see the fluorescence.
Well done.
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[*] posted on 21-9-2020 at 04:20


Quote: Originally posted by unionised  
KNO3 will convert the Cr2O3 to chromate so I can't see that helping.
The best thing I can think of to support your Al2O3 / Cr2O3 mix while melting it is more Al2O3.


I would expect KNO3 to form an aluminate.

From memory they use florides as fluxes.




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

Old codger' lives matters, wear a mask and help save them.
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metalresearcher
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[*] posted on 22-9-2020 at 02:19


I tried again, but now with a larger pile of Al2O3 / Cr2O3 mixture, preventing the arc reaching the floor (on which the pile is) which melts and contaminates. And I avoided touching the powder and the molten ruby with the carbon rods.
Much better results now.
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wg48temp9
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[*] posted on 22-9-2020 at 03:12


Quote: Originally posted by metalresearcher  
I tried again, but now with a larger pile of Al2O3 / Cr2O3 mixture, preventing the arc reaching the floor (on which the pile is) which melts and contaminates. And I avoided touching the powder and the molten ruby with the carbon rods.
Much better results now.


Can we see pictures in ordinary light and UV please.

PS: Some carbon gouging rods have a core that contains salts preferably you should use the plain ones.

[Edited on 9/22/2020 by wg48temp9]




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

Old codger' lives matters, wear a mask and help save them.
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[*] posted on 22-9-2020 at 11:17


Here they are, they are about 12mm large.

My carbon rods are pure carbon, no salts inside and no copper cladding.

RX606836.JPG - 2.3MBRX606837.JPG - 1.8MB
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[*] posted on 22-9-2020 at 13:09


Thanks mr. Those ruby nuggets are spectacular.



i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

Old codger' lives matters, wear a mask and help save them.
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[*] posted on 23-9-2020 at 05:09


now make blue saphires idk what does that tho maybe cobalt??
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[*] posted on 24-9-2020 at 03:37


FeO and TiO2, don't know if the FeO can survive high temperature heating in air though.
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[*] posted on 24-9-2020 at 11:49


I have done some rubies and found this has helped:
Mix the chrome and aluminum oxides with a small amount of fluoride-containing flux (silver brazing flux) with a small amount of water to make a clay-like paste. Let that dry completely and it will form a fairly sturdy piece that will not blow apart when you hit it with the arc. I got tired of the powdery piles blowing all over the place. I also found I was able to achieve some fluorescence by heading the "ceramic" with a maxed out blow torch (no supplemental oxygen). It doesn't get intensely pink but "pinkish" and it glows slightly under UV.
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[*] posted on 25-9-2020 at 23:50


The idea of making a kind of pellets is very good to prevent the arc blowing away the powder.
But why fluoride containing flux ? You mean CaF2 ? And using lower melting salts (e.g. NaCl or CaCl2) as a flux ?
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[*] posted on 26-9-2020 at 00:16


Quote: Originally posted by metalresearcher  
The idea of making a kind of pellets is very good to prevent the arc blowing away the powder.
But why fluoride containing flux ? You mean CaF2 ? And using lower melting salts (e.g. NaCl or CaCl2) as a flux ?


Yes the solidifying the powder is a good idea.

I would avoid a flux unless you know its ions do not quench the fluorescence. Perhaps chromium nitrate or aluminium nitrate could be used as a binder. They should decompose at relatively low temperatures to leave the oxide that should hold the main aluminium oxide ingredient together.




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

Old codger' lives matters, wear a mask and help save them.
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[*] posted on 26-9-2020 at 16:00


Quote: Originally posted by metalresearcher  
The idea of making a kind of pellets is very good to prevent the arc blowing away the powder.
But why fluoride containing flux ? You mean CaF2 ? And using lower melting salts (e.g. NaCl or CaCl2) as a flux ?


No reason other than I was trying different things and the brazing flux I had happened to contain NaF. Since PbF2 is used in the flux growth process I thought I'd give it a try. I cant say if the flux helped but making the puck certainly did. The biggest problem is foaming. The ruby melt gets lots of entrained gasses causing it to puff up and bubble, making it opaque. So many times I thought I had a nice large piece that turned out to be a big disappointing bubble.
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