science behind making efficient firecrackers of BP and FP (please read if you're a chemist)

April 1, 2020

Hi! This is my first post.

I'm currently making firecrackers. I have both kno3,mg flash powder and black powder, but i mainly want to make BP firecrackers because of high supply.

I need to know the science behind how both BP and FP act when being compressed or in a fluffy state, and how to create the best boom. I've read somewhere on this forum that BP should be compressed, while flash not. I've also read that if you compress BP in a small enough space, it will explode. Is this correct? You usually compress powders when you want to make rockets and such.

Does compressed BP act differently when there's no way for gas to escape, which creates compression in the air?

I've also experimented with damp BP, and it seems to burn "almost" as fast as flash powder. I'm only using powder btw, not granulated. The reason behind why it burns faster is because the volume increases (it becomes more fluffy) so hot air/gases can easily pass through the small particles, thus creating faster fire rate.

Also, some say you should leave about 1/3 part of empty space in the firecracker. I think this is because you want as much of the explosive to burn up before it breaks the shell, so you get maximum amount of pressure.

So, is it best to compress or leave it fluffy. My opinion is to leave it fluffy so that it will fire a lot quicker, but if this "explode when it's compressed" is not true, then i should stick to damp BP because it burned the fastest of all the tests i did in open air.

April 1, 2020

Well I'm no chemist, but this isn't really a chemistry question. I'm sure others will chime in with the usual safety/legality warnings in terms of making "firecrackers," so I'll skip those other than to say, be careful and respect laws and neighbors.

As for your question, you seem to be confusing "compressing" and "confining" composition. Compressing bp will slow its burn rate as it is harder for the flame to propagate between the grains. Assume all things are equal, adjusting grain size is the best way to tweak burn rate for BP. Compressing flash powder is unnecessary and dangerous due to the friction involved.

BP will make a good boom but it requires a good deal of confinement. Black powder maroons are basically firecrackers that work by heavily confining black powder by wrapping a small "box" of bp in twine. These are safer than working with flash and still quite loud.

Typical perchlorate/aluminum flash powder burns much, much faster than bp, so it needs little to no confinement to make a boom. The same properties that make it loud make it dangerous. Please proceed with caution.

April 1, 2020

Yeah, i'm currently using mortar and pestle, and it's not a fun job i must say.

I'm not confusing compression with confinement, it's just the way i've been reading about black powder, it seems that magic happens if you compress it good enough, because the chemicals are tightly pressed into each other and combined with high pressure will make the chemical reaction so fast it would explode. Of course, without the gas pressure it would burn slowly. I think the reasons i've failed so many times is because i haven't sealed it good enough, the BP would just bend open the fusehole and spit fire. I'm using empty ammunition shells, large ones. I made a pretty good bang with one, but i had to bore a fusehole in the middle instead of the fuse going on the top, so the BP would burn faster. I did compress it, i believe.

However, right now i'm out of ammunition, so i've rolled a few mini firecrackers with kraft paper and using dextrin/wheat mix for glue for sealing. Do you think this will work? Currently drying the bottom part, will fill them tomorrow and glue top part. I will try different BP batches and pressing techniques to see which works the best.

Edited April 1, 2020 by DoodieSmoothie

April 2, 2020

ABOVE ALL - be safe.

The only "crackers" I've ever made was using a small amount of granulated BP. Never FP - way too dangerous for me.

I used an empty dunny roll (expensive now ) I folded it a triangular shape leaving a good air cavity inside.

I inserted the fuse through a small hole, from the inside first. The fuse also contained the BP charge at the end in a "bulb" shape - wrapped in thin paper.

I glued and wrapped it glass tape.

Nice "Bang" for sure. I loved it

Just please be careful whatever you do.

April 2, 2020

Yeah, i'm currently using mortar and pestle, and it's not a fun job i must say.
I'm not confusing compression with confinement, it's just the way i've been reading about black powder, it seems that magic happens if you compress it good enough, because the chemicals are tightly pressed into each other and combined with high pressure will make the chemical reaction so fast it would explode. Of course, without the gas pressure it would burn slowly. I think the reasons i've failed so many times is because i haven't sealed it good enough, the BP would just bend open the fusehole and spit fire. I'm using empty ammunition shells, large ones. I made a pretty good bang with one, but i had to bore a fusehole in the middle instead of the fuse going on the top, so the BP would burn faster. I did compress it, i believe.

However, right now i'm out of ammunition, so i've rolled a few mini firecrackers with kraft paper and using dextrin/wheat mix for glue for sealing. Do you think this will work? Currently drying the bottom part, will fill them tomorrow and glue top part. I will try different BP batches and pressing techniques to see which works the best.

When you say you're using a mortar and pestle I hope you mean for grinding your bp chems individually and nothing else. I only say this because I know there is an abundance of terrible information online including videos of people doing things like mixing flash in a mortar and pestle, or even in a blender. If you value you life don't do that.

Also, when you say you are using empty ammo cases do you mean that you are loading metal tubes with explosives? Using a metal case for a firecracker is dangerous, dumb, and likely to get you charged with building bombs should you encounter any type of law enforcement. Paper is safe, paper is cheap, paper works.

I still think there are some wires being crossed with your ideas regarding compression. I'm not sure if you have some bad information, or if you are misunderstanding what you are reading. The chems in your black powder need to be intimately mixed, but they don't need to be pressed into each other. Maybe you were reading something about granulating powder by pucking and corning? There is an important difference between pressure that is applied to a composition to consolidate it, and pressure generated from a composition burning while confined. Compression will slow black powder's burn rate. Think about it this way: what burns faster an ounce of bp in a loose pile or an ounce of bp tightly consolidated in a rocket tube? Per my earlier comment about granulation size, what burns faster a pile of black powder dust, or pile of small granules? As an example of pressure from combustion affecting burn rate, think about the difference between burning a single strand of black match vs that same piece of match confined in a leader tube.

It sounds like you may be loading dust into a tube and not some form of granulated bp. Is that the case?

Please don't take this the wrong way, but based on your questions it seems like you are very new to this. It's good that you are asking questions but I'm a bit concerned that you are experimenting, potentially dangerously, without fully understanding the risks and variables you are playing with. I'm no expert myself, but I've learned enough over my last couple years in this hobby to recognize that I did some very stupid things when I first got started. So start slow and stay safe.

April 3, 2020

When you say you're using a mortar and pestle I hope you mean for grinding your bp chems individually and nothing else. I only say this because I know there is an abundance of terrible information online including videos of people doing things like mixing flash in a mortar and pestle, or even in a blender. If you value you life don't do that.

Also, when you say you are using empty ammo cases do you mean that you are loading metal tubes with explosives? Using a metal case for a firecracker is dangerous, dumb, and likely to get you charged with building bombs should you encounter any type of law enforcement. Paper is safe, paper is cheap, paper works.

I still think there are some wires being crossed with your ideas regarding compression. I'm not sure if you have some bad information, or if you are misunderstanding what you are reading. The chems in your black powder need to be intimately mixed, but they don't need to be pressed into each other. Maybe you were reading something about granulating powder by pucking and corning? There is an important difference between pressure that is applied to a composition to consolidate it, and pressure generated from a composition burning while confined. Compression will slow black powder's burn rate. Think about it this way: what burns faster an ounce of bp in a loose pile or an ounce of bp tightly consolidated in a rocket tube? Per my earlier comment about granulation size, what burns faster a pile of black powder dust, or pile of small granules? As an example of pressure from combustion affecting burn rate, think about the difference between burning a single strand of black match vs that same piece of match confined in a leader tube.

It sounds like you may be loading dust into a tube and not some form of granulated bp. Is that the case?

Please don't take this the wrong way, but based on your questions it seems like you are very new to this. It's good that you are asking questions but I'm a bit concerned that you are experimenting, potentially dangerously, without fully understanding the risks and variables you are playing with. I'm no expert myself, but I've learned enough over my last couple years in this hobby to recognize that I did some very stupid things when I first got started. So start slow and stay safe.

I'm fairly new to this, but i have experimented with match firecrackers with ammunition when i was younger. I thought my FP would burst the metal into pieces but it doesn't. It just rips it open in the middle.

Thanks for warning me but, i know mixing flash powder in my mortar&pestle is a bad idea. However, i do grind black powder. I've figured out it's pretty safe, and if it were to ignite, it would only burn a gram or two. I need to grind small batches at a time to achieve meal powder.

But after doing a bit of reading, i'm starting to think that rammed meal powder is the best way for making BP expldoe.

Quote from https://www.amateurpyro.com/forums/topic/6592-firecracker-help/ "you can use BP in firecrackers. The trick is to either ram mealpowder really hard and use strong endplugs of bentonite or to use corned powder loose in a tube but still with strong endplugs but of wood or very thick cardboard."

And from this website https://www.pyrocreations.com/Pyrotechnic-Blog/black_powder_rockets, it says that for rockets you need to perfectly measure out the nozzle gap so that it won't get too much air pressure inside the rocket fuel room, because the more pressure it gets, the faster the BP will burn. So did we learn that magic happens when you combine compressed BP and air pressure?

I tested my different BP firecrackers that was both rammed, loose, and had air pockets inside. And for all 3 firecrackers, i had the exact same problem as the guy on the other forum, "firecracker would spit fire out fuse hole". Not only fuse hole but also the ends. I don't think dextrin mixture works good for end plugs or maybe i use too little. Also the paper thickness on the firecracker is too big compared to how much BP i can fit inside it. It's not enough to break the shell . It worked like a charm with flash though.

I should find a way to make good end plugs first, then test again, but i don't know any easy way. I don't have a ramming tool, but i do have cat litter. Do i have to use something that matches the inside diameter of tube, or can i go with something smaller i can find around the house to ram cat litter?

I tested 2 more now that i rammed, and it made a small bang because the end plugs went flying out.

Any tips on strong homemade plugs? Planning to use cat litter as base, then for the top i will be using toiletpaper+hotglue, or multiple layers with kraft paper + hotglue.

Edited April 4, 2020 by DoodieSmoothie

April 4, 2020

I've always made my firecrackers to resemble the Chinese made

firecrackers I enjoyed as a teen. I cut strips of newspaper or

some other similar paper about 1 1/4 inch wide and about 12

inches long. I then wind the strip into a tube using a pencil as

the core and paste the end of the paper strip to the tube to

prevent its unwinding.

Remove the tube from the pencil and crimp one end of the

tube to close it off. The crimp is done by pushing some of

the paper down into the center of the tube end with a small

screwdriver. Alternatively, the end of the tube can be pinched

and tied with string to close it.

Fill the tube about half way with meal powder, insert fuse,

then crimp that end of the tube or pinch it closed and

tie with string.

I make my own fuse for firecrackers with tissue paper just

as the Chinese do.

All of the firecrackers I got from China back then (50s) were

crimped at the ends I hadn't ever seen any made with

powdered clay end plugs until recently. It seems the way

they're made today in China has changed.

Edited April 4, 2020 by SeaMonkey

April 4, 2020

I'm fairly new to this, but i have experimented with match firecrackers with ammunition when i was younger. I thought my FP would burst the metal into pieces but it doesn't. It just rips it open in the middle.

Thanks for warning me but, i know mixing flash powder in my mortar&pestle is a bad idea. However, i do grind black powder. I've figured out it's pretty safe, and if it were to ignite, it would only burn a gram or two. I need to grind small batches at a time to achieve meal powder.

But after doing a bit of reading, i'm starting to think that rammed meal powder is the best way for making BP expldoe.
Quote from https://www.amateurpyro.com/forums/topic/6592-firecracker-help/ "you can use BP in firecrackers. The trick is to either ram mealpowder really hard and use strong endplugs of bentonite or to use corned powder loose in a tube but still with strong endplugs but of wood or very thick cardboard."
And from this website https://www.pyrocreations.com/Pyrotechnic-Blog/black_powder_rockets, it says that for rockets you need to perfectly measure out the nozzle gap so that it won't get too much air pressure inside the rocket fuel room, because the more pressure it gets, the faster the BP will burn. So did we learn that magic happens when you combine compressed BP and air pressure?

I tested my different BP firecrackers that was both rammed, loose, and had air pockets inside. And for all 3 firecrackers, i had the exact same problem as the guy on the other forum, "firecracker would spit fire out fuse hole". Not only fuse hole but also the ends. I don't think dextrin mixture works good for end plugs or maybe i use too little. Also the paper thickness on the firecracker is too big compared to how much BP i can fit inside it. It's not enough to break the shell . It worked like a charm with flash though.
I should find a way to make good end plugs first, then test again, but i don't know any easy way. I don't have a ramming tool, but i do have cat litter. Do i have to use something that matches the inside diameter of tube, or can i go with something smaller i can find around the house?

I tested 2 more now that i rammed, and it made a small bang because the end plugs went flying out.
Any tips on strong homemade plugs? Planning to use cat litter as base, then for the top i will be using toiletpaper+hotglue, or multiple layers with kraft paper + hotglue.

I'm not going to take the time to explain, again, what you are misunderstanding, why you are wrong, and why you are doing things both inefficiently and dangerously. It's clear you asked your initial question not wanting answers but encouragement. So I'll just point out a couple things from the links you cite:

From pyrocreations: "A paper tube is used as a casing. Under no circumstances be tempted to use materials other than paper. It is dangerous and unnecessary."

From the APC thread: "ramming the bp will not make a firecracker, and it will not woosh out unless you have loose bp meal or slow powder and or the fuse hole is too big."

"It may have seemed pretty dense, but they were very likely not rammed. Think about the other things that are made from rammed BP, like spolettes and rockets. Sure, rockets can CATO if the nozzle is too small, but I can assure you that not all the BP is consumed. The other thing that makes them CATO is cracks, IE a higher surface area."

"After checking some vids on professional firecracker making on YT I must admit that you guys are right about not ramming the BP."

Good luck.

"

April 4, 2020

Thank you, i just needed someone to validate it because there's people saying 2 different things so i get confused. ^_^

May 26, 2020

Reading the posts above made my gut hurt.

May 28, 2020

Reading the posts above made my gut hurt.

Yeah, dude, don't get into this hobby if all you want to do is make things go boom. It's that attitude that makes the CPSC make things ever more restrictive--plus, it's what gets you labeled as a "potential terrorist" whenever you inevitably blow your hand off/burn your garage down, and they paint all of us with a broad brush.

Take some time to learn about the hobby, there's a massive wealth of resources out there but rushing in just wanting to blow things up is a surefire way to wind up being a statistic, a cautionary tale, and yet another black mark on the hobby in the popular mindset.

It's also a great way to get the cops to your house, rifling through everything you own and perhaps discovering your other, ahem, less-than-legal hobbies.

May 28, 2020

Yeah, dude, don't get into this hobby if all you want to do is make things go boom. It's that attitude that makes the CPSC make things ever more restrictive--plus, it's what gets you labeled as a "potential terrorist" whenever you inevitably blow your hand off/burn your garage down, and they paint all of us with a broad brush.

Take some time to learn about the hobby, there's a massive wealth of resources out there but rushing in just wanting to blow things up is a surefire way to wind up being a statistic, a cautionary tale, and yet another black mark on the hobby in the popular mindset.

It's also a great way to get the cops to your house, rifling through everything you own and perhaps discovering your other, ahem, less-than-legal hobbies.

Seen a guy on YTube today grinding chlorate and al on concrete with a metal spoon. Wasn't sure I was gonna be able to remove my chair from my clinched cheeks. Everything I read above gave me the same feeling.

May 28, 2020

Did any of you happen to notice the posting date?

May 29, 2020

Did any of you happen to notice the posting date?

Yup. It's all about the conversation.

May 29, 2020

Yup. It's all about the conversation.

Ya know...while it IS amusing... I belong to a few BBQ sites as well. admin a rather popular one. And this crops up every year. i just worry that some fool WILL try split railroad ties one day.

May 29, 2020

Ya know...while it IS amusing... I belong to a few BBQ sites as well. admin a rather popular one. And this crops up every year. i just worry that some fool WILL try split railroad ties one day.

hmm. I'll have to think on that one.

June 6, 2020

After reading what you had to say in the first 2 things you posted, i am exteramly surprized anybofy gave you any help! I read that you have a mortor and pastel! You will not make very good black powder that way! I i really hope for your sake that the fp doesnt end up in there! 2, you said mg and kno3 flash powder! That is not a safe flash powder to make! You need to do more reserch, it is all out there do the work and you might survive! I will tell you this, mg does not create a oxide layer on the mg that protects it from further oxidization! Which means when you add it to the kno3 it will start to oxidize and continue to do so until one day you blow your house up! To use mg i believe you can treate it with a rather toxic dichromate that will stop this from happening! Im 40 and have been interested in pyro for 25 years! Most of those i fidnt actually get into the hobby, as in i played around with homemade bp and sugar and kno3 when i was 15 but nothing burned fast enough to kill me as i didnt have access to the internet where all the info that you have found so far is readily available! If i did have access at that age to the knowlage i can access now i probably wouldnt have made it to 18 years of age! BE CAREFUL FLASH POWDER IS NOT FOR KIDS AND IS CLASSED AS A HIGH EXPLOSIVE! 200G HAS THE POTENTIAL TO NOT ONLY KILL YOU BUT YOU NEIBOURS TOO! I cant scream it loud enough in text! But if your asking these questions you should not be making flash powder!

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science behind making efficient firecrackers of BP and FP (please read if you're a chemist)

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