Why so much charcoal in organic stars?

[Potassiumchlorate]

Is it just for ignitability? There is often 12-13% of it in organic green and red.

 

I know that there is 5% charcoal and sulfur respectively in many metallic ones too, but sulfur doesn't "wash out" the colour like charcoal does, and the metallic fuels in these stars improve the colour so much that the charcoal in them doesn't matter.

 

Or is it that the manufacturers are pennywise? I have this old (and not recommendable) formula for a green Bengal fire:

 

barium chlorate 44

sulfur 23

charcoal 12

potassium nitrate 14

antimony trisulfide 7

 

This is of course cheaper and was even more so back in the days when barium chlorate was more expensive, but I doubt that it's as good as the 9:1 formula with Ba(ClO₃)₂ and shellac.

Edited October 10, 2011 by Potassiumchlorate

[Peret]

I'm not the ace chemist around here, but I'll hazard a guess that the charcoal plays a role as a reducing agent, to discourage the production of metal oxides at the expense of chlorides.

[Mumbles]

I'm not sure where you're finding formulas containing 12-13%, but I suggest looking toward more contemporary sources. The better formulas typically have less than 2-3%. Typically it is added in small amounts to smooth the burn of the star, improve ignition, and I suppose to some extent shift the fuel balance.

[Potassiumchlorate]

That formula was from 1955, and I'm not intending to use it anyway, but I have this one from Bleser, which probably isn't that old:

 

Bleser Red#1

 

Potassium chlorate 38

Strontium nitrate 38

Red gum 6

Charcoal 12

Hexachlorobenzene 2

Dextrin 4

[Mumbles]

That's actually Blesser Red #2, but I'll be darned. I guess I never paid that close of attention to the Blesser formulas. There is a green formula with an oddly high charcoal content in there too. I'll have to go back and look at some of these sources. I did notice that it only seems to be done with chlorate stars however. They shouldn't need the ignition help, and at this high of a level it seem like a straight fuel, not just added for the benefits it has.

[Potassiumchlorate]

I'm pretty satisfied with those of Bleser's compositions that I have tested this far: red, green and white Mg fueled, aqua, organic violet and New Blue. I think the man is under-estimated.

[californiapyro]

isnt new blue a copper benzoate formula?

[Potassiumchlorate]

isnt new blue a copper benzoate formula?

 

Yup. I went a bit off topic. What I wanted to say is that I'm overall satisfied with Bleser's compositions, no matter what kind they are.

[wvpyro]

I thought I would add my own two cents:

 

The formula given would be EXTREMELY HAZARDOUS and shouldn't be compounded by anyone. Barium chlorate is dangerous with any fuel, and the extra sensitivity from the sulfur and sulfide make it absolutely unacceptable.

 

That being said, the composition has other theoretical problems. Potassium nitrate shouldn't be added to any color formula where the monochlorides are created in the flame for color production (blue, green, red). It is a chlorine scavenger and also a low temperature oxidizer. Both characteristics are deleterious to color (there is a reason it is almost unheard of in color formulas, with the possible exception of yellow). The antimony is also found in white stars, so the composition is like mixing a green formula with a white formula. Wouldn't be sensible even if one were so reckless as to use the composition.

 

The Bleser red is simply Weingart's cut/pumped/candle star with a little chlorine donor. A similar green can be made with barium nitrate, but it's not nearly as good as a barium chlorate green. PVC works if HCB isn't available. Too much destroys the color. The charcoal is preferentially very fine willow. Regular hardwood airfloat may be problematic, especially for the green. The ratio of oxidizers can be juggled to adjust burning speed. Less chlorate will slow down the stars.

 

Barry Bush has 11.5% charcoal in one of his perchlorate greens (in Hardt), but he admits the color is "poor."

[Potassiumchlorate]

I stated clearly that I'm not intending to use that green formula. I just gave an example. And the best organic green is of course barium chlorate/shellac.

 

Like I said it's from a 1955 encyclopedia, and the composition itself is probably much older.

[50AE]

My guess would be cost. Charcoal is a cheap fuel.

 

Barium chlorate/shellac does make a great green, but potassium chlorate should be added to cheapen, increase ignition reliability and burnrate to the formula. Barium nitrate can be also added to reduce cost. The addition of these doesn't destroy the color noticeably.

Edited October 15, 2011 by 50AE

[Potassiumchlorate]

What if I switch the ratios of charcoal and red gum, i.e. 12% red gum and 6% charcoal or at least take equal parts, i.e. 9% of each?

 

I also don't have HCB but I do have HCE. I think that in big and/or pumped stars it doesn't evaporate so quickly, so it might function as an extra chlorine donor, maybe even better than HCB, despite its volatility.

[50AE]

It won't work well if you switch fuels. Red gum has more fuel value than carbon.

[Potassiumchlorate]

Yes, I know that the fuel value will change, but will it change so much that it will destroy the effect? The star will burn faster, but that doesn't have to be a problem.

 

Stochiometrically the simplest organic red star would be:

 

Poatssium chlorate 43

Strontium nitrate 43

Shellac 14

 

Though these kind of stars are hard to ignite. Same with barium chlorate/shellac 88:12, which is a very powerful composition once ignited.

Edited October 19, 2011 by Potassiumchlorate

[Potassiumchlorate]

Uppdate:

 

I made a 10 gram test batch of the Bleser formula. I don't have HCB but I do have HCE, but I skipped it for the moment and used PVC instead. It's only 2%, so it's not that crucial, I believe.

 

Made eight (or seven and a half to be precise) 10 mm pumped stars. Small leftover crumbles of the composition burned with a nice deep red colour even when moist.

[Arthur]

Most of the UK fireworks forums are currently full of people looking to buy the cheapest fireworks, or the most firework for their money, so the ingredients WILL suffer. Manufacturers need product that works and they need it for the best price to get sales so compounds have to be chosen with a strong emphasis on cost, and charcoal costs less that many chemicals.

 

For exhibition purposes the cost may mean less, for amateur constructors cost may mean almost nothing, both looking for the best performance. Formulations will vary according to the cost constraints.

 

UK compounds have been cheapened with charcoal or wood meal for years for retail purposes but these are not used for professional product.

[Potassiumchlorate]

But Bleser is American and a hobbyist and it seems to be a good comp.

 

But yes, that old composition from 1955 or probably earlier was obviously for consumers. Down to 43% barium chlorate was common in old green consumers' fireworks, and barium chlorate was used only because magnesium and magnalium were even more expensive than barium chlorate back then, while green exhibition fireworks contained up to 90% barium chlorate.

[Potassiumchlorate]

*BUMP*

 

I think I found out why it is so much charcoal in this particular comp. It goes back to a Browne composition from around 1870:

 

Strontium nitrate 8

Potassium chlorate 4

Washed sulfur 3

Chertier's copper ½

Shellac ½

Fine charcoal _1/4

 

In percentage this will be:

 

Strontium nitrate 49.2

Potassium chlorate 24.6

Washed sulfur 18.5

Chertier's copper 3.1

Shellac 3.1

Fine charcoal 1.5

 

If you remove the very dangerous Chertier's copper and make the percentage of strontium nitrate and potassium chlorate equal and round it off a bit, you will get:

 

Strontium nitrate 38

Potassium chlorate 38

Washed sulfur 19

Shellac 3.5

Fine charcoal 1.5

 

If you remove the sulfur from this and substitute it with 10% charcoal, 3% shellac and 3% dextrin, you'll almost exactly get the Weingart formula, that the Bleser formula is based upon.