13 replies to this topic

[digger]

Interesting. I have not come across this statement before about the Dichromate.

By the way I stock the oxychloride.

[Mumbles]

I've only heard of doing this with MgAl formulas in an attempt to protect the metal. I suppose it could work, but it sounds like crap to me. A catalyzed reaction doesn't release any less energy, and will probably burn faster. To be fair, I've heard this statement before, but just am not sure of the truth behind it.

[al93535]

Dichromate does catalyse the decomposition of perchlorate. I do not see how it would make a blue any more vivid, in fact I would guess that the increase in burn speed would make the star hotter and therefore wash out the blue!

In my opinion there is way to much PVC in that formula. You can drop the sulfur and the potassium nitrate too.

If I were to make an organic blue star I would use something like:

Potassium perchlorate 63
Black copper oxide 10
Saran resin 10
red gum 4
Hexamine 9
Dextrin 4

Of course you can also use Ammonium perchlorate to make an excellent blue star but they do burn slowly!

On another note, I would use dichromate for only one reason, to protect magnesium from being attacked by ammonium perchlorate! It is the only really useable coating for Mg and NH4ClO4. Its too toxic for its mundane protection on anything else.

[MDH]

A mixture of potassium dichromate and sulfur alone actually burns a surprisingly deep blue. I imagine as a lone oxidizers, dichromates would make interesting colors. But I doubt that as a catalyst it does more than simply lower the ignition point of the star. From my personal experience dichromates have no effect on nitrate compositions.

The potassium nitrate, I am guessing, is to act as a temperature moderating agent an an oxidizer both at once, creating saturation of an energy that requires more to decompose. In the "old days" of pyrotechnics they used agents such as ammonium or potassium sulfate even in blues and greens to lower the temperature if the composition was organic.

Edited by MDH, 23 April 2010 - 05:23 AM.

[al93535]

Dichromate and sulfur huh? Interesting, I might have to try that out.

You can add magnesium carbonate to cool the composition as well. But this had better be a stand alone firework, as any other stars/effects are going to vastly outshine these!

We make quite nice blues at work and use mgal in them. Of course when the blues are up against reds and greens at 12% to 14% mgal, tey have to have some metal content!

[Arthur Brown]

With the reported toxicity of dichromates, I'd be very cautious of spraying aqueous dichromates in any way that could could put them in aerosol ready to breathe, mask or no mask. Aerosols pass right down into the lungs, just one place where I don't want dichromates.

[Mumbles]

Well, sulfur alone burns as a nice blue. I recall some people many years ago trying to add granular sulfur to comets and fountains to try to get a blue tail. It's very dim up against even charcoal streamers. On top of this, the sulfur just melts and never is ejected. The dichromate probably wouldn't add any color to this, just some oxygen and speed everything up. Ammonium dichromate burns on it's own with no smoke, and really no flame to produce Cr2O3, N2 and water.

[pyromaniac303]

Perhaps when it was stated they were comparable to chlorate blue, it was the flame size and not the flame colour they were comparing? Chlorate flame envelopes are typically larger than perchlorate ones, which in turn makes the colour appear brighter but not specifically deeper.

[digger]

Pretty much what I thought about that one.

[Mumbles]

Did you notice any change in the burn speed of the two stars?