A couple phenomenon I am very curious to understand the workings of.

[Alex W.]

Now, I didn't get any footage of it, and I could change that, but, I did a slag run, which I decided to do because I had a lot of aluminum come out with the slag I pulled out on a couple melts, which I retrieved about five or six muffin ingots of from about two liters of.

I added borax to help separate the aluminum and the slag, seeing as that's what it's usually used for.  But after I let it sit for a while to do it's thing if it even does at this point, chunks of slag started glowing hotter and hotter, behaving like pieces of magnesium, getting brighter and brighter, and started emitting smoke as the whole top of the slag layer was glowing nearly white hot.  And that prompted me to immediately remove the crucible and start taking out the slag out of fear I might max out the crucible's temperature rating, not knowing if it would continue getting brighter to the point it hurts my crucible, and it slowly died down, both inside and out of the crucible, and it was very powdery with a lot of crumbly chunks.  

I was running the foundry, as I had found out later, very lean on fuel, so there was a lot of excess oxygen in the air mix, which seemed to help, I turned the fuel injection up and it seemed to dim a bit, so I think that may be a factor.  

I know that aluminum is used in explosives as a fine powder, and that it reacts with water when it is mixed with gallium which compromises the oxide layer it forms with contact with air, like when it's a liquid as with gallium or a melt.  So, as a completely original guess I made up on my own, I'm wondering if somehow, as a result of the borax being added, and excessive temperatures, it was able to burn whatever aluminum was trapped in the slag at the time and give off a white glow, and, as I forgot to mention, what seemed to be a little  bit of white flame.  But, as is almost always the case, it isn't the truth, or even close, so, I am asking if anybody over here understands what's going on. 

But when it comes to this next effect which I observed, I am a little more confident I am correct with my guess as to what's going on, but regardless, I think it looks pretty cool.  Pretty much every time I melt scrap that has paint on it, or something else that burns off(I can't remey if it does it otherwise hehe) there's this weird blue glow around the slag, especially when I pull out the crucible to pull out slag and pour it, and I'm thinking it is all the carbon in the slag that's left over from the burnt paint.  Is this a correct estimation of what's going on, or is there another weird explanation for this propane stove flame colored glow?

And, one more thing, does quenched slag usually smell like raw eggs?  I think the yellow green paint on the majority of my scrap had sulfur in it, and I think it is a factor in the amount of blue glow around the slag in my scrap melts, it seemed a lot more profound, but that's probably because of the increase in size of my crucible, but I'm not quite sure.

Anyway, thank you for reading this, I hope I haven't been a bore, and have a good day.(sorry I don't have any footage of this, I think I'll get some some time)  

 

Also, here is the slag I pulled out after melting it a second time:

 

Edited June 19, 2020 by Alex W.
I forgot a couple details

[Charles dP]

This video might shed some light... plus it’s quite cool.

[Jerrod Miller]

In addition to Charles' link:  Everything burns with a different color.  So there are a wide array of colors of flames that you may see coming off, depending on what contaminant is oxidizing (burning).  It is even possible that you can see a crazy looking flame that isn't all that hot.