N1 glitter star comp. and stoichiometry question-ish

[PillaDoubleG]

Sorry for flooding these threads with so many questions, but I just have so many.

I recently learned stoichiometry, so I wanted to try an oxygen balance equation (I think that's what it's called)on some star comps, to see if they have enough oxidizer in them.
Took the N1 glitter comp, cuz it's my favorite so far, and calculated everything, and in the end I got 36.6%. I was really weirded out when I saw this, because, if I didn't make any mistakes, that is SUPER under-oxidized, there should be at least double the amount of oxidizer to burn up all of that fuel. Now as I said, I could've just done the calculations wrong, but I'm about 90% sure that they are right.

For context, I took all of the chemical equations for each chemical, calculated the molar value of the oxygen produced/let off (for the oxidizer), added up the molar mass of the oxygen that the fuels reacted with, and in the end divided the oxygen given by the oxidizer with the reacting oxygen.

Thank you to anyone that may help! If you need more context I will try to provide it to you.

[Arthur]

Stoichiometry is only part of the story! Look at BP and Tiger tail same ingredients different ratio, so the falling star has to use the air it's falling through for oxidation.

[cmjlab]

FAST (Takeo Shimizu), Pyrotechnics (A. Hardt), Chemistry of Pyrotechnics. (J. Conklin), and Shidlovsky (brain farted the title), are all literature that discuss chemistry of pyro.  Similar to what Aurthur is saying, Stoichiometry.seems to be good when developing formulas to give you a starting point, but requires testing to get the result you want as there are often environmental factors and complex bi-products adding to the reaction. Lastly, it also seems to be good for theoretical chemistry (much like a theoretical yield is rarely the actual yield an equation produces).

  

Edited December 27, 2023 by cmjlab

[PillaDoubleG]

Thanks for replying so fast, explained everything. 

 

[Arthur]

A Stoichiometrically correct formula will react as fast as possible which for BP and flash is OK but for effects could well be much too fast. A star lasting milliseconds would be a bit pointless, most stars need to burn for 1 to 5 seconds.

[Zumber]

For stoichiometry and balancing reactions and more deeply studying.

Find Kosanke publications.

[PillaDoubleG]

Since this thread is related, what formula should be used to describe charcoal? I know many people use C, but in my case I use C20H7O, since that's what Takeo Shimizu recommends. But I have found many more... The last one in the image should be the most accurate, but it's far more complicated than the others.

[Arthur]

The trouble with real world pyro is that the ingredients and their impurities differ by the batch and these matter, for BP especially we assume that charcoal is charred wood but then we also say that the type of wood matters, probably the fibrous nature of the wood matters too, willow, oak, teak and mahogany are all woods but only willow of those makes working BP charcoal. This is why pyrotechnics is always part art and part science. 

[cmjlab]

Sidlovski is pretty well respected, and his formula accounts for just the Carbon and moisture content - it'd be a good baseline.  There would likely still be unaccounted for volatiles in the charcoal, since we don't cook charcoal to the temperature or duration to be just Carbon, but there's no way to account for everything.

[PillaDoubleG]

Aha... I see. What would the reaction look like when reacting charcoal with oxygen, using the Sidlovski formula?

[cmjlab]

 

Sorry I misread the chemical abbreviation, I thought it said C6H20 as in 6 atoms of Carbon and 2 atoms of hydrogen and one of oxygen.  It in fact is referring to 6 Carbons and 20 Hydrogen.  

With that correction, I am speaking above my knowledge level.  Maybe someone with more of a formal chemistry background can help you.

Sorry for the confusion

[AustralianPyromaniac]

"Volatile" content in charcoal can be as high as 40% when made at low temperatures, charocal for black powder is made as low as 300c, which does seem to improve the quality of the powder, with volatiles increasing the rate of flame propagation. Volatile content is normally between 20%-40% if the charcoal is made for pyrotechnic use. We have no idea what these volatiles are between batches, and they vary between wood species and baking conditions.

I'm a little confused about how 20 hydrogens could get in there though. As the size of organic molecules increases, the ratio of hydrogen to carbon falls. I would expect the volatile components to be large and complex hydrocarbons along with a small amount of water, which really could not achieve that ratio of hydrogen to carbon. It may be a misprint of C6H2O. The final O I think is actually a O not a 0. 

Regarding the question on what the reaction would be, the products of the combustion of charcoal are CO2 and H2O. You can easily balance that reaction based on whichever formula for charcoal you pick. But the reaction taking place in the real world is far more complex, when KNO3 and S are present, sulfides and SO2 are formed, along with K2CO3, all of which require some of the oxygen. 

When designing formulas, gillters and streamers tend to be very fuel-rich, and color stars slightly fuel rich, really for different reasons. If you have a specific goal in mind, balancing and stoichiometry can be important, but generally, it is not so useful. 

[Mumbles]

There is a book called "Glitter: Chemistry and Techniques" by Lloyd Scott Oglesby that would be incredibly useful to the conversation here.  He goes through some stoichiometry balancing practices and examples specific for glitters, and discusses some of the chemistry behind the effect that is really helpful to understand some aspects of this.  

Pyrotechnic stoichiometry is difficult.  There are often a number of competing reaction pathways and products.  BP for example may look fairly simple as a composition, but there are over 30 different products generated.  

With regard to charcoal itself, I don't have a complete understanding of it, but do understand some of the basics.  Wood at a high, generalized level is composed of cellulose (~45%), lignin (~25-35%), salts, and other organics.  The other organics would be things like sugars, resins, etc.  All of these have their own decomposition pathways, temperatures, and products.  The salts generally become "ash", and comprises about 4-20% of the final mass of charcoal, so probably .5-5% of wood.  You can get an estimate of the ash content by washing it with acid.  Generally speaking, lower pyrolysis temperatures leave more "volatile" material behind.  You can usually get an estimate of the volatiles in your charcoal by extracting it with acetone and measuring the residue of the extract (which is usually a sticky red or brown tar).   The hotter and longer you cook charcoal, it's generally believed to become more carbon enriched and generally more graphitic in structure.  

Trying to fully understand all the aspects that go into good charcoal for pyrotechnics could take a lifetime.  There are a huge number of variables.  I've just accepted that it's kind of black magic, and the more important thing is to have a process or supply that works for you.