102 replies to this topic

[pyrotechnist]

Has anyone tried metal carbonate based colours using MgAl as the sole oxidizer and fuel? I have tried strontium which seems to give a very bright pretty quick burning red and sodium bicarb which burns with an immense bright yellow light. Calcium carbonate needs a little bit of tuning to get it right with copper carbonate just burning a bright white. Though it does seem you can create colours, especially orange and yellow without an expensive oxidizer such as Perc.

[CCH Concepts]

how hard were they to light, are you actually using the carbonate as the oxidizer?

[pyrotechnist]

Pretty easy to light but extremely bright and hot, I would assume the MgAl would be the oxidizer but not sure as I aint a chemical mad head lol . It would appear to be like a negative reaction. I do seem to have acheived reasonable colours from it though.

[CCH Concepts]

how did you decide on your ratios and did you add a chlorine donor?

[vaslop2005]

Pretty easy to light but extremely bright and hot, I would assume the MgAl would be the oxidizer but not sure as I aint a chemical mad head lol . It would appear to be like a negative reaction. I do seem to have acheived reasonable colours from it though.

you are actualy using the carbonate as an oxdiser for the magnesium;

SrCO3+2Mg+2Al--->SrO+2MgO+2Al+C

you might notice that the Aluminium doesnt burn at all and their is carbon released, making for an intense flame when it reaches the atmospheric oxygen. about 6 months ago when I tried this, I used Mg granules, and got the same results. but found that adding about 5-10% PVC was well worth it. I'd be interested to see if you can make any kind of blue though, as this reaction will be way too hot and fast for a conventional star.

[pyrotechnist]

I find KNO3 slows the reaction down somewhat but you are right they do make pretty decent and extremely cheap colours. No wonder they can be slaggy if the aluminium is left behind.

My formula was:

Metal Carbonate ------------ 30
MgAl 200 - 300 # ----------- 50
KNO3 ----------------------- 10
Parlon --------------------- 10

The best by far is sodium bicarbonate yellow! as it seems to hit the perfect yellow spot of the sodiums light spectrum without that orange tint to it.

Edited by pyrotechnist, 24 June 2010 - 08:11 AM.

[CCH Concepts]

that would make sence about the Al, Mg is a higher reactivity and lower melting point. i assum its simply reacting first, but im sure it would work with or and use up all metal, just not both. maybe a different metal as a fuel might burn cooler?

some of the negitive flashes use Mg/MgSO4, maybe something similar with the copper, could copper be used as a fuel? i swear i read that most metals could be somewhere

[vaslop2005]

that would make sence about the Al, Mg is a higher reactivity and lower melting point. i assum its simply reacting first, but im sure it would work with or and use up all metal, just not both. maybe a different metal as a fuel might burn cooler?

some of the negitive flashes use Mg/MgSO4, maybe something similar with the copper, could copper be used as a fuel? i swear i read that most metals could be somewhere

Magnesium (and other reactive metals) are the only fuels that react with carbonates, as when a carbonate decomposes Na2CO3--->Na2O+CO2, the magnesium reacts with the carbon dioxide, and leaves carbon behind. Aluminium isn't reactive enough to displace the carbon, (and neither is copper)

[pyrotechnist]

I assume this could be used for flares or very bright stars.

[pyrotechnist]

I am going to have to make some stars using this mixture and test them out at a far distance to see how practical they are.

[Mumbles]

Just because he balanced it without aluminum being used up doesn't mean it actually works that way. The aluminum could react with the metal oxide left over in a goldschmidt like reaction. The end result is still the same I suppose.

I'd be a little worried about the huge amount of excess carbon. The incadescence can be distracting to colors. I suppose when they're this bright, it doesn't really matter too much.

I'll see if I can find them. I have some patents or papers somewhere on very similar reactions used for flares. They of course used perchlorates as a secondary oxidizer to make them burn smoother.

[pyrotechnist]

Well I got my personal formula from a bit of testing and trying out Neds rubber rainbow star formulas which are mainly:

Perc -------- 30
MgAl -------- 30
Metal Carb -- 20
Parlon ------ 15
Red Gum ----- 5

I did try the red of this formula a few times and it seemed to produce a similar bright red to the metal carbonate version without using perc as the oxidizer so I thought why use an expensive oxidizer if you can get workable results without it.

[vaslop2005]

Just because he balanced it without aluminum being used up doesn't mean it actually works that way. The aluminum could react with the metal oxide left over in a goldschmidt like reaction. The end result is still the same I suppose.

I'd be a little worried about the huge amount of excess carbon. The incadescence can be distracting to colors. I suppose when they're this bright, it doesn't really matter too much.

I'll see if I can find them. I have some patents or papers somewhere on very similar reactions used for flares. They of course used perchlorates as a secondary oxidizer to make them burn smoother.

their is no way that the sodium, barium and strontium oxides will react with aluminium, their electronegativity (reactivity) is way too high, and the aluminium is just oxidised by atmospheric oxygen, however with copper carbonate it will be oxidised, but this won't produce any colour.

I would be interested to see how potassium carbonate/hydrogen carbonate would work as a 'base oxidiser' and then colour producers added to this. If anyone has experience with this?

[pyrotechnist]

I have potassium carbonate, the only problem with it is its hygroscopic nature. So do you use it as a secondary oxidizer with the colour producers and metal?

[pyrotechnist]

I have potassium carbonate, the only problem with it is its hygroscopic nature. So do you use it as a secondary oxidizer with the colour producers and metal?