23 replies to this topic

[Creepin_pyro]

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Edited by Creepin_pyro, 20 September 2011 - 04:37 PM.

[MDH]

Is there a variant without copper metal? What would the burning time be of a 4mm star?

Edited by MDH, 10 February 2011 - 11:15 PM.

[Creepin_pyro]

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Edited by Creepin_pyro, 20 September 2011 - 04:38 PM.

[T-sec]

I haven't tried a varient without the Cu, no. At the moment it's slow burning and suitable only for burning on the ground. My plan is to get it working as stars if possible.

Any updates in the mean time, getting the mixture working in stars?

[Creepin_pyro]

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Edited by Creepin_pyro, 20 September 2011 - 04:38 PM.

[RegimentalPyro]

While browsing the passfire forums I found the following post which explains how strobes work....Credit to the original poster (Mike Swisher)

The mechanism of strobe compositions' burning was explained by Dr. Shimizu in his Pyrotechnica article long ago.

Their burning has a smoulder phase and a flash phase. These are produced either by the use of two oxidizers or by the use of a binary fuel (magnesium/aluminum oxide). In the ammonia strobe compositions, ammonium perchlorate is the smoulder oxidizer and the metal sulphate is the flash oxidizer. Sulphates are sluggish oxidizers and have high heats of decomposition. Ammonium perchlorate, which requires little heat input to release its oxygen, helps the mixture smoulder along until enough heat has built up in the semi-reacted mass to cause the sulphate to give up its oxygen, triggering the flash reaction.

The barium nitrate/magnalium/sulphur strobes function somewhat differently. In them, the magnesium of the magnalium is a smoulder fuel. It keeps smouldering away with the sulphur (which acts both as a fuel and a secondary oxidizer) until the flash reaction takes place between the aluminum and the barium nitrate.

Crackle is a subcategory of the latter type of strobe. In it, the magnesium of the magnalium is the smoulder fuel; the oxidizer is a higher oxide of a transition metal such as lead or bismuth, which has more than one oxidation state. The smoulder reaction partially reduces the lead or bismuth oxide to a lower oxidation state; heat builds up in the semi-reacted mass until the flash reaction takes place between the aluminum and the lower oxide. In crackle, however, the flash reaction is so violent as to prevent any semi-reacted composition from remaining to propagate continued burning.

This is, needless to say, a sort of thumbnail sketch of Shimizu's explanation. You should read his articles.

The short summary is, though, that you can't just take a composition that gives a good color in continuous burning and modify it to be a strobe. There must be specific ingredients that bring about alternating smoulder and flash phases - either a low- and high-temperature oxidizer (such as ammonium perchlorate and a metal sulphate) or a low- and high-temperature fuel (such as magnesium and aluminum, conveniently alloyed together in magnalium). There are a few odd exceptions (I recall a German, perhaps Wassmann, who developed a non-metallic strobe), but they have not been successfully applied in fireworks to much extent.

[Creepin_pyro]

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Edited by Creepin_pyro, 20 September 2011 - 04:38 PM.

[MDH]

A story from my chemistry experimental days is that I reacted an unnamed chinese brand of soap with copper sulfate to form copper fatty acid salts. Combined with potassium perchlorate (not anything else) in perticular fuel-rich formulas, an organic strobe resulted. Combining with sulfur and other fuels would kill the strobe. To the day I have been trying to search for what brand of soap was used in that experiment, as it only happened once! But I would imagine it is a mixture of vastly long chain fatty acids with only the tiniest amount of short-chain to enhance the product's aroma.

[Mumbles]

I've seen such formulas once. I really don't remember where though, and it's been driving me nuts for years. As far as I recall, there was a relatively high level of sulfur and hexachlorobenzene. I've heard people say that parlon could be made to work as well. It seems it needs that low fuel value chlorine donor, presumably for color production and to kind of "clog" things up.

Edited by Mumbles, 12 July 2011 - 04:28 AM.

[Potassium chlorate]

I've seen such formulas once. I really don't remember where though, and it's been driving me nuts for years. As far as I recall, there was a relatively high level of sulfur and hexachlorobenzene. I've heard people say that parlon could be made to work as well. It seems it needs that low fuel value chlorine donor, presumably for color production and to kind of "clog" things up.

We discussed Chinese Blue#1 some year or two ago:

potassium perchlorate 39
copper(II)oxide 37
sulfur 15
hexachlorobenzene 7
red gum 2

I tried it with HCE instead of HCB, since HCB is as good as impossible to get hold of in Europe. Not remarkably blue but as blue as Conkling etc anyway. Hardt prime#6 for ignition, NC as a binder.

[digger]

A story from my chemistry experimental days is that I reacted an unnamed chinese brand of soap with copper sulfate to form copper fatty acid salts. Combined with potassium perchlorate (not anything else) in perticular fuel-rich formulas, an organic strobe resulted. Combining with sulfur and other fuels would kill the strobe. To the day I have been trying to search for what brand of soap was used in that experiment, as it only happened once! But I would imagine it is a mixture of vastly long chain fatty acids with only the tiniest amount of short-chain to enhance the product's aroma.

What do you call vastly long?

As you will be aware I work in the oils and fats industry. I have little knowledge of soap ingredients.

I would guess the range would be somewhat limited from C10 to C20 with only traces either side. As many true soaps (not filled SLS and glycerine etc) are made from veg oils there are only a few choices regarding fatty acid spread. Better quailty soaps would tend to use lauric oils such as coconut or palm kernal which have a profile C8 8% , C10 6%, C12:47%, C14 17.5%, c16 9% an C18:0 to C18:3 12%. Palm oil based would be C16 45%, with the rest mainly falling in C18:0 to C18:3. If it was really cheap (would not be now) then it would fall in the softs category which would be C16 4% and the rest falling in the C18:0 to C18:3 range. Obviously there will be small quantities of other components, but they are small.

You could always hydrolise vegetable oils to gain their fatty acids and react to get your favoured metal soap.

Edited by digger, 13 July 2011 - 01:28 PM.

[Mumbles]

We discussed Chinese Blue#1 some year or two ago: potassium perchlorate 39copper(II)oxide 37sulfur 15hexachlorobenzene 7red gum 2I tried it with HCE instead of HCB, since HCB is as good as impossible to get hold of in Europe. Not remarkably blue but as blue as Conkling etc anyway. Hardt prime#6 for ignition, NC as a binder.

I don't know how much it would matter, but that's not the formula as originally given.

Chinese deep violet-blue microstars
Source: Myke Stanbridge / Rec.pyro

Potassium perchlorate to pass #240 39.0
Black copper oxide to pass #240 37.0
precipitated sulphur to pass #240 15.0
Hexachlorobenzene (HCB) to pass #60 6.5
Acacia gum, a top quality fine dust 2.5


I'm not sure how large you made them, but it's fairly well known that it only works as micro stars. In larger sizes, it tends to get washed out. HCE is probably the closest replacement we have, but it's hard to judge without seeing the real deal first.

[Creepin_pyro]

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Edited by Creepin_pyro, 20 September 2011 - 04:38 PM.

[Potassium chlorate]

I don't know how much it would matter, but that's not the formula as originally given.

Chinese deep violet-blue microstars
Source: Myke Stanbridge / Rec.pyro

Potassium perchlorate to pass #240 39.0
Black copper oxide to pass #240 37.0
precipitated sulphur to pass #240 15.0
Hexachlorobenzene (HCB) to pass #60 6.5
Acacia gum, a top quality fine dust 2.5


I'm not sure how large you made them, but it's fairly well known that it only works as micro stars. In larger sizes, it tends to get washed out. HCE is probably the closest replacement we have, but it's hard to judge without seeing the real deal first.

Akacia gum is called Arab gum or Gummi Arabicum here. I could buy some and test it.

I made 8mm pumped stars, which probably is way too big.

[pyrotrev]

Akacia gum is called Arab gum or Gummi Arabicum here. I could buy some and test it.

I made 8mm pumped stars, which probably is way too big.

I had a play with that sort of mixture a while back, it produces a huge amount of ash, for a star burnt on the ground really a cinder which if small enough allows CuCl vapour to escape and shine blue. I would guess 3...4mm is the biggest star you could make, which probably explains why there's some very good blues in bombettes/inserts but not in bigger shells