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Author: Subject: Charcoal size for BP - super fine vs "air-float"
RogueRose
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[*] posted on 17-7-2016 at 23:08
Charcoal size for BP - super fine vs "air-float"


I've read that there are a number of variables that play a role in good BP and particle size is one of these and grinding/milling when mixed is another.

I have used charcoal dust that was put through a coffee filter (the super fine brass mesh that are re-useable). I also setup a canister filter to go inline with a vacuum hose. The charcoal will be smashed/pounded in a covered container and the vacuum will pull air/dust from the top of the container into the filter canister. This same thing could be done with a blender/food processer or coffee grinder with the vacuum sucking in the dust when taking the lid off after grinding.

I would suspect the particle size of the charcoal is much smaller in the air-float and wonder how much difference there may be in quality of the BP made with particles of this size.

As a note, all the ingredients of the BP can be made with air-float ingredients, it just takes much longer to collect everything with a home size setup.
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[*] posted on 17-7-2016 at 23:13


Quote: Originally posted by RogueRose  
I've read that there are a number of variables that play a role in good BP and particle size is one of these and grinding/milling when mixed is another.

I have used charcoal dust that was put through a coffee filter (the super fine brass mesh that are re-useable). I also setup a canister filter to go inline with a vacuum hose. The charcoal will be smashed/pounded in a covered container and the vacuum will pull air/dust from the top of the container into the filter canister. This same thing could be done with a blender/food processer or coffee grinder with the vacuum sucking in the dust when taking the lid off after grinding.

I would suspect the particle size of the charcoal is much smaller in the air-float and wonder how much difference there may be in quality of the BP made with particles of this size.

As a note, all the ingredients of the BP can be made with air-float ingredients, it just takes much longer to collect everything with a home size setup.


Black powder has more to depend on what type of wood the charcoal has come from than how fine it is. You can use superfine charcoal powder from briquets or activated carbon and your BP will still be bad. The best charcoal is still one made yourself from willow wood. (Not the trunk, rather smaller branches not thicker than your wrist)
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[*] posted on 18-7-2016 at 05:48


Well, the more finely divided the charcoal, the greater the possibility for an intimately mixed composition.

I have used air-float mixed hardwood charcoal with great success. ;)

[Edited on 18-7-2016 by Loptr]
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[*] posted on 18-7-2016 at 07:31


Deathunter88 is correct about charcoal WOOD SPECIES and CARBONIZATION CONDITIONS being of greater concern than the particle size BEFORE processing. As in, willow, european black alder (yo, those buck thorn weed trees in the USA), grape vine, hemp stalks or other known appropriate vegetable sources, carbonized at the lowest temperature and for the minimum time, not having been overheated and having all traces of volatiles driven off with remaining Carbon reduced to something like graphite in structure (graphite does not burn well, have not tried diamonds yet, but the milling media would probably wear out PDQ...)

If you are going to mill the powder, be it in an edge runner mill, ball mill or (heavens, how quaint) a stamp mill, you are going to take care of any slightly oversize particles of charcoal.

For CIA powder variants, you are going to ball mill the Sulfur and charcoal together anyhow, so again, it can be a bit coarser than AF grade.

Commercial AF was the stuff that blew away, or fell through the screens from the other screened grades the charcoal plant was making, you know? It was a waste material from other processes usually, not something they set out to make. Sure, they sold it to fireworks manufacturers, but civil/entertainment pyrotechnics has never been a big enough industry to have their own purpose built, dedicated supply chains of materials, we improvise from whatever is available out there industrially already from the suppliers to higher dollar industries- or scavenge over runs and surplus from military pyrotechnic manufacture. Asside from the times and places when BP made for the king's uses and he would lose battles if it was mucked up, we have always been the poor step children of industry.




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RogueRose
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[*] posted on 18-7-2016 at 12:48


Quote: Originally posted by Deathunter88  
Quote: Originally posted by RogueRose  
I've read that there are a number of variables that play a role in good BP and particle size is one of these and grinding/milling when mixed is another.

I have used charcoal dust that was put through a coffee filter (the super fine brass mesh that are re-useable). I also setup a canister filter to go inline with a vacuum hose. The charcoal will be smashed/pounded in a covered container and the vacuum will pull air/dust from the top of the container into the filter canister. This same thing could be done with a blender/food processer or coffee grinder with the vacuum sucking in the dust when taking the lid off after grinding.

I would suspect the particle size of the charcoal is much smaller in the air-float and wonder how much difference there may be in quality of the BP made with particles of this size.

As a note, all the ingredients of the BP can be made with air-float ingredients, it just takes much longer to collect everything with a home size setup.


Black powder has more to depend on what type of wood the charcoal has come from than how fine it is. You can use superfine charcoal powder from briquets or activated carbon and your BP will still be bad. The best charcoal is still one made yourself from willow wood. (Not the trunk, rather smaller branches not thicker than your wrist)


I have heard that willow is recommended as well but I have to question this, especially in a chemistry forum, as once it has been turned to charcoal and turned into a super-fine powder, how much difference can there be between most any charcoal source. In fact, just about any carbon source can be used in BP (like turning sugar into carbon with sulfuric acid). Charcoal is used in BP as a source of carbon not "charcoal" there is nothing special in charcoal other than it is an easily available and fairly pure form of carbon. IDK what is so special about willow wood except the fact that the bark has a small amount of "asprin" in it, which wouldn't make a difference in the wood and the tiny milligrams per ounces of bark isn't the factor.

As far as the BP being "bad" without willow is laughable IMO unless you can prove that there is something intrinsic about willow that all other charcoals don't have. I just read a number of pyro sites and they often use really soft wood like balsa, pine, grape vine and maple. The carbonization process burns off any VOC's in the wood so the sap's in the pine shouldn't remain.

I'm still thinking that particle size has more to do than anything in BP composition.
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[*] posted on 18-7-2016 at 12:56


Thanks to both DH88 and Bert for the analysis! I'll have to find some willow and do some experimentation. I have some oak charcoal dust and have used agriculture sulfur and the results have been amazing to say the least! I have compared it to commercial BP and I would say the mix I have produces much more "response" or "report" than when commercial BP was used in the same setup.

This calls for a back-to-back-to-back comparison (Commercial - Oak - Willow) the oak/willow made with same materials and mixing/blending times so all being equal. Now I just need a high speed video camera.
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[*] posted on 18-7-2016 at 12:56


Quote: Originally posted by RogueRose  
Quote: Originally posted by Deathunter88  
Quote: Originally posted by RogueRose  
I've read that there are a number of variables that play a role in good BP and particle size is one of these and grinding/milling when mixed is another.

I have used charcoal dust that was put through a coffee filter (the super fine brass mesh that are re-useable). I also setup a canister filter to go inline with a vacuum hose. The charcoal will be smashed/pounded in a covered container and the vacuum will pull air/dust from the top of the container into the filter canister. This same thing could be done with a blender/food processer or coffee grinder with the vacuum sucking in the dust when taking the lid off after grinding.

I would suspect the particle size of the charcoal is much smaller in the air-float and wonder how much difference there may be in quality of the BP made with particles of this size.

As a note, all the ingredients of the BP can be made with air-float ingredients, it just takes much longer to collect everything with a home size setup.


Black powder has more to depend on what type of wood the charcoal has come from than how fine it is. You can use superfine charcoal powder from briquets or activated carbon and your BP will still be bad. The best charcoal is still one made yourself from willow wood. (Not the trunk, rather smaller branches not thicker than your wrist)


I have heard that willow is recommended as well but I have to question this, especially in a chemistry forum, as once it has been turned to charcoal and turned into a super-fine powder, how much difference can there be between most any charcoal source. In fact, just about any carbon source can be used in BP (like turning sugar into carbon with sulfuric acid). Charcoal is used in BP as a source of carbon not "charcoal" there is nothing special in charcoal other than it is an easily available and fairly pure form of carbon. IDK what is so special about willow wood except the fact that the bark has a small amount of "asprin" in it, which wouldn't make a difference in the wood and the tiny milligrams per ounces of bark isn't the factor.

As far as the BP being "bad" without willow is laughable IMO unless you can prove that there is something intrinsic about willow that all other charcoals don't have. I just read a number of pyro sites and they often use really soft wood like balsa, pine, grape vine and maple. The carbonization process burns off any VOC's in the wood so the sap's in the pine shouldn't remain.

I'm still thinking that particle size has more to do than anything in BP composition.


Well if you're going to ball mill the mixture then charcoal size doesn't matter that much. Have a look at this webpage which has a very good process of making blackpowder starting from the proper charring of wood. http://www.musketeer.ch/blackpowder/homemade_bp.html
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[*] posted on 18-7-2016 at 16:44


Depending on the temperature of pyrolysis, the best charcoal is not pure carbon, but contains considerable amounts of hydrogen, oxygen, sulfur and other elements. Apart from chemical compositon, also physical effects likely play a role, were lignin, ash content, wood structure and carbonization temperature all influence the nanostructure of the charcoal produced. Its possible these structures are so small compared to obtained particle sizes from ballmilling, that they still play a big role. Iirc, ballmilling not only reduces particle sizes, but also helps more intimate contact between the components. Would be interesting to see if there is an optima7l designer material, like graphene nano tubules that would allow maximum contact between fuel and oxidizer.

Have milled and unmilled charcoal samples from different woods ever been studied with SEM or something, or surface area determined otherwise?

[Edited on 19-7-2016 by nitro-genes]
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[*] posted on 18-7-2016 at 17:18



Quote:
This calls for a back-to-back-to-back comparison (Commercial - Oak - Willow) the oak/willow made with same materials and mixing/blending times so all being equal. Now I just need a high speed video camera.


Nope. All you need is a 3" ID piece of pipe with a cap or plug on one end as a mortar and a baseball for a projectile, along with a stop watch.

Make black powder samples using your different charcoals, but with the exact same milling methods and pressed to the same density, screened for identical mesh ranges of finished grain size. Then weigh out some equal sized test charges (1 Oz. or 30 grams is likely a good size). Shoot the baseball up, record time from lift to landing. Compare. Clean the mortar every few shots, a narrowed dirty bore with a tighter fit to the projectile will give a spurious higher velocity reading.

Realize, your home made oak has probably been pressed to a different density and screened to a different grain size range than the commercial BP you compared it to. It's comparing apples to oranges unless you control all but one variable on such a test-




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[*] posted on 18-7-2016 at 18:53


Quote: Originally posted by Deathunter88  


Well if you're going to ball mill the mixture then charcoal size doesn't matter that much. Have a look at this webpage which has a very good process of making blackpowder starting from the proper charring of wood. http://www.musketeer.ch/blackpowder/homemade_bp.html


The black powder made in the link you provided is pretty lousy, the vessel used to make the charcoal isn't properly seals and it looks like part of the product has turned to ash, black powder made at home using this method should at least be on par with commercially made powder, if not better
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[*] posted on 18-7-2016 at 23:57


Quote: Originally posted by RogueRose  

Charcoal is used in BP as a source of carbon not "charcoal"

Wrong. The quality of black powder is highly dependent on the quality of the charcoal. This isn't an opinion, we have centuries of empirical experience supporting this.

Both the source of wood and he temperature it's been charred at is of great importance. Generally speaking the best woods are the soft hardwoods like willow and alder. The US obsession with willow is due to the use in commercial powder, but it's not the only alternative. It was just the best choice for a commercial plant when one considers quality and availability.
IIRC the german Wano-plant uses grey/black alder, while the swiss d'Aubonne uses alder buckthorn which is considered the best. It might be why the swiss powders is said to produce softer fouling.

The charring temperature is just as important. The ignition temperature of the charcoal increases with charring temperature, somewhere around 350-450°C is a good place to start. Old sources talks about "carbon rouge" which is "red charcoal" as a perfectly charred sample should have a faint brown/red tint.

I believe Shimizu reported a "heavily charred sample" so correspond to a formula of roughly C18H7O, a lightly charred product would contain even more hydrogen and oxygen.




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[*] posted on 19-7-2016 at 09:02


http://castboolits.gunloads.com/showthread.php?103852-My-hom...

This will give you more information on making black powder than you probably want....
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[*] posted on 19-7-2016 at 12:29


During the vast expanse of my rather uninteresting life, I've developed the opinion that if the source of powdered charcoal doesn't burn by itself in open air, then it's not going to burn well even once the oxidizer and sulfur are added.

I made the mistake once of using ultrafine graphite powder rather than charcoal. I figured that graphite was better because it was "purer". Of course, it did absolutely nothing. It wouldn't burn even if I blasted it with a torch. When I tried it with balsa wood charcoal, however..."foooomp"! A pile of graphite is non-flammable under normal conditions. A pile of ground balsa charcoal, on the other hand, will ignite and embers will chase all through the pile. The oxidizer just speeds up the reaction.




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[*] posted on 20-7-2016 at 04:54


From personal experience, small willow or black alder branches, bark removed before charring.

From personal observation of others fast, decent quality black powder lift charges, balsa (Skylighter used to sell the waste from one of the mills making model airplane balsa sheet and strip stock?), red cedar, small prunings of fruit woods such as plum and apple, (grape vine pruning charcoal made for quite good rocket fuel BP).

GOEX used maple at the old factory in Moosic, PA... Hard maple- Uniform, but not the best possible charcoal by any means. DuPont used willow, back in the day.





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[*] posted on 20-7-2016 at 06:08


I've had good luck with smaller than my wrist branches of corkscrew willow. Cato'ed a few rocket engines before I learned to tone it down a little with less clay in the nozzle.

[Edited on 20-7-2016 by hyfalcon]
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[*] posted on 20-7-2016 at 07:53


If your fuel is too snorty- Make the core just a bit bigger, and we don' need no steenkin' nozzles!

http://www.skylighter.com/fireworks/how-to-make/nozzleless-s...




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[*] posted on 20-7-2016 at 23:35


For application of BP as rocket fuel one does not need to make the fastest, hottest, high end mix with the best possible carbon available. In fact to achieve stability throughout motor units one has to steer in the opposite direction. A soft, relatively slow powder should be the goal and for that purpose most carbons are good enough. A slow fuel will be way more forgiving in terms of fluctuations in loading density, nicks and cracks on the core surface, imperfections in casing and nozzle dimensions and durability etc. In fact when it comes to making a successful rocket engine, the most important factor is paying detail to assembly procedure and keeping parameters constant throughout different units. Otherwise one can easily end up with batches that have a less than 50/50 success rate and powder performance may actually have very little fault in that. Considering the work involved in rocketry genre, this can get real frustrating real fast :)

When it comes to lift, burst, fuse and projectile charges the quality of carbon will play a paramount role in the performance of BP. As to which carbon is the best remains the target of endless debate and I guess everyone should just find the right combination through experimentation...
Constructing a temperature controlled pyrolysis chamber (electrical furnace e.g) will greatly ease the path to a surerior carbon and with nowadays access to low price components for that purpose it should not be a hard task for any BP enthusiast.




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[*] posted on 21-7-2016 at 00:59


Not that there is anything wrong with temperature control, finishing at constant temperature for say 30 minutes should even out inconsistencies quite well. But you don't need temperature control, assuming a repeatable setup (power, loading etc) the time should be fairly repeatable. The charring process is endothermic, so the temperature inside the retort will rise gradually, and the the final temperature is all you really need to get a predictable result.

Some use commercial charcoal (BBQ or whatnot) as they find cooking charcoal to complicated, but even a crudely made charcoal made from a good wood should be better than anything you can buy outside a pyro supplier. Batch-to-batch consistency can be hard, but by mixing batches one can even those out fairly well.

Complicated is fine, but not if it becomes an obstacle to actually doing anything.




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[*] posted on 21-7-2016 at 04:05


Black powder for rockets usually has less sulphur. My understanding is that the burn rate is less sensitive to pressure.

I'm also with markx but I'd go furthur, even for small arms fast powder is only one indicator of quality. Stability and shot to shot consistency are probably more important to a commercial producer.

Quote: Originally posted by Fulmen  
The charring process is endothermic, so the temperature inside the retort will rise gradually...


Amazingly enough, it's actually exothermic.
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[*] posted on 21-7-2016 at 06:31


You're right, it's exothermic. But I've never noticed any problems with regulating the temperature, probably due to heat loss in the setup or that it's only exothermic within a small range.



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[*] posted on 21-7-2016 at 12:59


The subject of *exothermic* pyrolysis of wood caught my eye, and I found this interesting dissertation:

https://deepblue.lib.umich.edu/bitstream/handle/2027.42/6075...

It would appear that wood pyrolysis can be net endothermic or exothermic, with an early endothermic stage, followed by an exothermic one leading to a temperature spike.



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[*] posted on 21-7-2016 at 13:47


For me...Nothing is better than airborne C-black of fumes...
K chlorate blackpowder made with it deflagrates in the open in less than 3g and detonates 5mm wall tickness pipe bombs...charcoal dust from electrical coffee grinder never acheive such results and looks like a fierce bengale fire.




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[*] posted on 21-7-2016 at 13:50


Nice find. Looking at the temperature data on page 76 it seems there is indeed both endothermic and exothermic areas. But at lower temperatures the exothermic reaction is fairly small, so slow cooking seems to be the best approach.



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