Black Powder burning speed x charcoal

February 8, 2020

So, I tested 3 different charcoals, here are the results. But first I will describe the method I used, I know it is not the more realiable and accurate method, but it was the easiest one for me.

My burn-rate method: spread 5g of BP on a V shaped iron. The trail must have 30cm of lenght. Just light it from one end of the trail and record a slow motion video (I recorded a 240fps video). Then count the frames it takes to burn through 30cm completely, calculate the time and burning speed of the BP.

Disadvantages of this method:

- some spark may jump forward and burn the trail much faster

- the burning BP is so bright that it is hard to know exactly when it finished burning

Advantages:

- easy and fast to do the experiment

- accurate enough for me

*all my BPs were granulated using 50% isopropil alcohol, without dextrin, and using a 18 mesh sieve.

Results:

1) BP from eucaliptus briquette charcoal: 13cm/s

2) BP from cheap activated charcoal: 25cm/s

3) BP from common eucalyptus barbecue charcoal: 37cm/s

Discussion:

I compared my results with the ones found in this link http://www.wichitabuggywhip.com/fireworks/charcoal_tests.html

Most of the BPs from this link burn faster then 37cm/s. So I may be doing something wrong or my components are not the best ones. What I think I can improve:

a) I just milled the 3 components together (75-15-10) for about 3 hours. I could mill them longer. (I milled KNO3 and charcoal separatelly for about 24 hours)

the charcoal I have is from hardwood. I could make my own charcoal from other trees.

c) KNO3 is very difficult to buy in Brazil. So I bought a fertilizer grade KNO3, you can see its composition on the attached picture. Do you think I should try to purify this KNO3?

in any case, despite still being a newbie in this pyrotechnics world, with this simple test I could see the importance of the charcoal used to make BP.

Edited February 8, 2020 by jimjones

February 8, 2020

I would increase the charcoal parts from 15 to 18 or 20 and see what that does.

What are your milling details?

February 9, 2020

I use coconut shell charcoal , dunno how it affects to the burn rate but it works for me

February 9, 2020

As JV asked, what are your milling details?

Mill type? Jar size/diameter/capacity? Milling media type/size/volume of jar? Milling rotational speed? How much bp/run? They all make a big difference. In a small hobbyist mill, for example, even with ideal media and loading, 3 hrs seems too short to produce optimal BP. If you pulled a sample at 2 hr, 3 hr, 4 hr...and compared burn rates (don't even bother granulating at this point), you'll know if you've reached optimal milling time for your composition.

In contrast to JV's suggestion of changing out charcoal concentrations, I'd probably wait to play with that variable until you get a reproducibly fast bp. Optimize milling conditions at typical 75/15/10 to get the fastest possible with your lump eucalyptus charcoal. If it's not good enough, then you'll need a new charcoal. The eucalyptus might be ok for gerbs/groundwork, etc., even if the BP isn't fast enough for rocket fuel or burst/lift.

Many agricultural KNO₃s are pure enough not to need refinement; it's impossible to tell from the label of yours whether there are any minor ingredients--it says 100%. If it's in prilled form (hard pellets), there may be a small amount of binder. If so, this may become apparent if you dissolve some in water--any precipitant or sediment would suggest an inert binder. Probably your KNO₃ is just fine.

Is your BP completely dry??? And how are you drying it? You might get a surprising increase in burn rate if you store it with some dessicant packets for a day or two (whether commercial silica gel or homemade with CaCl₂, for example). You could weigh a small container of your "dry" BP before/after dessication, after granulation. You might be surprised to find that your BP has not completely dried yet. Even with 50% alcohol granulation, your BP can still be damp long after the alcohol smell is gone, depending on your drying method. Slow drying methods might allow larger nitrate crystals to form, which can reduce burn rate.

If you get clumping with extended (8-12 hour) milling, then possibly your charcoal and/or KNO₃has absorbed moisture, which can be baked out of it in the oven before mixing (please do not ever consider drying BP in an oven...). It's summer in the Sao Paulo area, and humid. I typically bake my nitrate and charcoal and store with dessicant packets in airtight containers; if I don't use either within a month, they get baked again before use.

Tell us about your milling conditions and granulated BP drying method, please.

February 10, 2020

Milling Detais

I built a ball milling (see attached picture). The motor is much faster and more powerfull than needed for a mill this size. I always run the mill under 120 RPM, so the balls form a kind of "waterfall". Usually between 60 and 90 rpm, but I don't know the exact number.

I have two plastic jars one has 13cm of diameter and 1.7L (see picture) and the other has 8cm of diameter and about 0.5L.

The rule of thumb that I'm using is to fill about 30% of the jar with balls and pour the material to be grinded until the jar is half full.

I first mill charcoal and KNO3 separetelly:

I let them mill for 24 hours. I use the big jar for that. The balls I'm using in this jar are steel balls mixed with glass marbles. Their diameter range from about 8mm to 20mm.

PS: after some hours milling, the KNO3 starts to clump.

Then mill the 3 components together:

I put 75mg of KNO3, 15g of charcoal and 10g of sulphur in the smaller jar, and mill slowly for about 3 hours. The balls I'm using in this jar are common glass marbles some have 1cm and some 2cm of diameter.

BP granulation:

After milling 100g of BP, I pour a little less than 30g of 50% isopropil alcoholl and rub this "dough" BP on a 18 mesh sieve. The granules fall on a metal tray and I let it dry inside home near a window, but on the shadow. The temperature here is warm, about 25C (77F) at the moment. After some hours, when it feels dry by the touch, I put the BP in a sealed container.

Additional tests:

I have a 80 mesh screen and a 200 mesh screen, so I got a small sample of the components and "studied" the granulometry of the milled charcoal, the milled KNO3 and the sulphur. The charcoal and KNO3 both passes the 80 mesh screen after milling (more than 99% is passing), but about 30% of them doesn`t pass the 200 mesh screen. The sulphur is very fine already and more than 99% pass the 200 mesh screen.

Thanks for the suggestion. I will do that to find the optimal milling time.

If you pulled a sample at 2 hr, 3 hr, 4 hr...and compared burn rates (don't even bother granulating at this point), you'll know if you've reached optimal milling time for your composition.

As JV asked, what are your milling details?

Mill type? Jar size/diameter/capacity? Milling media type/size/volume of jar? Milling rotational speed? How much bp/run? They all make a big difference. In a small hobbyist mill, for example, even with ideal media and loading, 3 hrs seems too short to produce optimal BP. If you pulled a sample at 2 hr, 3 hr, 4 hr...and compared burn rates (don't even bother granulating at this point), you'll know if you've reached optimal milling time for your composition.

In contrast to JV's suggestion of changing out charcoal concentrations, I'd probably wait to play with that variable until you get a reproducibly fast bp. Optimize milling conditions at typical 75/15/10 to get the fastest possible with your lump eucalyptus charcoal. If it's not good enough, then you'll need a new charcoal. The eucalyptus might be ok for gerbs/groundwork, etc., even if the BP isn't fast enough for rocket fuel or burst/lift.

Many agricultural KNO₃s are pure enough not to need refinement; it's impossible to tell from the label of yours whether there are any minor ingredients--it says 100%. If it's in prilled form (hard pellets), there may be a small amount of binder. If so, this may become apparent if you dissolve some in water--any precipitant or sediment would suggest an inert binder. Probably your KNO₃ is just fine.

Is your BP completely dry??? And how are you drying it? You might get a surprising increase in burn rate if you store it with some dessicant packets for a day or two (whether commercial silica gel or homemade with CaCl₂, for example). You could weigh a small container of your "dry" BP before/after dessication, after granulation. You might be surprised to find that your BP has not completely dried yet. Even with 50% alcohol granulation, your BP can still be damp long after the alcohol smell is gone, depending on your drying method. Slow drying methods might allow larger nitrate crystals to form, which can reduce burn rate.

If you get clumping with extended (8-12 hour) milling, then possibly your charcoal and/or KNO₃has absorbed moisture, which can be baked out of it in the oven before mixing (please do not ever consider drying BP in an oven...). It's summer in the Sao Paulo area, and humid. I typically bake my nitrate and charcoal and store with dessicant packets in airtight containers; if I don't use either within a month, they get baked again before use.

Tell us about your milling conditions and granulated BP drying method, please.

February 10, 2020

Milling Detais
IMG_20200209_204003.png
I built a ball milling (see attached picture). The motor is much faster and more powerfull than needed for a mill this size. I always run the mill under 120 RPM, so the balls form a kind of "waterfall". Usually between 60 and 90 rpm, but I don't know the exact number.
I have two plastic jars one has 13cm of diameter and 1.7L (see picture) and the other has 8cm of diameter and about 0.5L.
The rule of thumb that I'm using is to fill about 30% of the jar with balls and pour the material to be grinded until the jar is half full.

I first mill charcoal and KNO3 separetelly:
I let them mill for 24 hours. I use the big jar for that. The balls I'm using in this jar are steel balls mixed with glass marbles. Their diameter range from about 8mm to 20mm.
PS: after some hours milling, the KNO3 starts to clump.

Then mill the 3 components together:
I put 75mg of KNO3, 15g of charcoal and 10g of sulphur in the smaller jar, and mill slowly for about 3 hours. The balls I'm using in this jar are common glass marbles some have 1cm and some 2cm of diameter.

BP granulation:
After milling 100g of BP, I pour a little less than 30g of 50% isopropil alcoholl and rub this "dough" BP on a 18 mesh sieve. The granules fall on a metal tray and I let it dry inside home near a window, but on the shadow. The temperature here is warm, about 25C (77F) at the moment. After some hours, when it feels dry by the touch, I put the BP in a sealed container.

Additional tests:
I have a 80 mesh screen and a 200 mesh screen, so I got a small sample of the components and "studied" the granulometry of the milled charcoal, the milled KNO3 and the sulphur. The charcoal and KNO3 both passes the 80 mesh screen after milling (more than 99% is passing), but about 30% of them doesn`t pass the 200 mesh screen. The sulphur is very fine already and more than 99% pass the 200 mesh screen.

Thanks for the suggestion. I will do that to find the optimal milling time.

Your two jars will not spin the same rate because they are different diameters. Marbles are rather lightweight media and 3 hrs milling time is almost definitely not sufficient for optimal BP. Take caution with using marbles. Although I have used them when a complete newbie, if you search this and other forums, you will find examples of glass media causing problems. Those can include 1) potential sparking, especially with glass containing metal salts for coloring (never experienced this) and 2) glass chipping off irregularly shaped pieces that might have sharp edges and cause friction issues, especially when hand-ramming rockets, for example. In over 100 runs with glass marbles, I never had an issue--that is my experience and absolutely not a guarantee of safety. I use lead .50 caliber musket balls (1/2 inch; 12.7 mm diameter) and this cut my milling time in half for the fastest BP my charcoal would provide.

Usually, people fill the jars halfway full with media, and approximately 1/4 full with BP components--most of this will fit between the holes of the spherical milling media, so your jar is still only 1/2 full after adding chems + media. It seems you are not using enough milling media (marbles), and I'd increase it to half the jar instead of 30% volume.

It seems to me that 30 g alcohol/water to 100 g BP would make an overly wet mix. Wet it just until it is able to form a coherent solid clump. Then, massage it well for 5 minutes at least, to uniformly wet and mix all components (this is even more important when adding binders like dextrin). Strongly suggest granulating through an 8 or 10 mesh screen, at minimum, instead of an 18-mesh screen, which will produce many granules much smaller than 18 mesh. You can always re-screen to make smaller granules. I am guessing your BP is too wet, and you are possibly granulating it too small and too soon--photos would assist us here.

"Dry to the touch" is definitely not dry!!! Granulated BP can contain a significant amount of water in it and still feel "dry to the touch", but not be!!! It almost definitely requires more drying. I am 99% positive that if you stored it with some dessicant packets with color-sensitive beads, you would immediately see an increase in burn rate. That said, your eucalyptus charcoal still might not be good enough for rockets/lift/burst. Maybe it is, maybe it isn't. You won't know until you optimize it, and you have not yet done so.

Use more milling media. Mill for a longer time. Don't overwet your BP. Massage it like bread dough for 5 minutes at least to completely incorporate/wet your mix in a uniform fashion. Dry your BP as fast as is practical, in the sun or under a fan. Dry your BP completely. Find a bigger mesh screen for granulation (any hardware store has this); 18-mesh is too damned small for initial granulation. Forget about the two slower charcoals you tested--they are shit. Your eucalyptus might be, also, but you won't know until you have extracted maximum capability from it, which you have not yet done. It might be sufficient, or, quite possibly, it is just not good pyro charcoal and you will need to continue your search.

Please report back on your modifications and your results.

February 10, 2020

Eucalyptus is supposed to be a great charcoal for BP. I'm assuming the charcoal you have is for use in a grill? It may be possible to re-cook it in a retort to drive off the remaining volatiles.

February 10, 2020

It is possible that eucalyptus might work, although reports besides http://wichitabuggywhip.com/fireworks/charcoal_tests.html seem to be very limited (Neighbor, do you have any other references at hand?). And others have had shit luck using eucalyptus: https://www.amateurpyro.com/forums/topic/2926-performance-rockets/?hl=eucalyptus . So the results are not consistent or conclusive. Search "eucalyptus" on this forum, and I think you'll find that very few of our Aussie friends (please chime in) use eucalyptus for pyro charcoal, and that is where eucalyptus originally comes from (not Brasil--it was imported to South America, primarily to make charcoal for cooking purposes--not pyro). Also, there are literally hundreds of species of Eucalyptus to complicate the matter, so it can be difficult to compare experiences when the precise species is not known or stated.

Since you already have eucalyptus lump charcoal, as NJ says, it is really no trouble to give it an additional brief retort and then retest it. As stated earlier by others, bbq lump charcoal is typically undercooked compared to pyro charcoal, to retain more of the flavorful volatile chemicals. This makes tasty food, but slower BP. So fill a coffee can with your charcoal, seal it tightly, poke a hole in the top, heat it up, and see if flammable vapors are still emitted. If so, cook it until the vapors stop, seal it up from atmospheric oxygen and let it cool down, and retest your charcoal. If there is improved speed, excellent--but is it sufficient for your needs? If it is good enough, fantastic! If not, you will still need to find an alternate source of softwood for making decent pyro charcoal.

Please report back.

Edited February 10, 2020 by SharkWhisperer

February 10, 2020

Charcoal can absorb moisture, so making sure it's dry before making the powder mixture up is probably a good idea.

NJ and SW, the popular wisdom is that it's the volatiles contained in the charcoal that give BP its speed. Shimizu suggests a carbon content of 70-80% for black powder charcoal. It seems that you guys don't agree that the volatiles are an asset?

February 10, 2020

For a number of years Ulrich Bretscher in Switzerland maintained a series of

web pages with just about everything we need to know about Black Powder.

His original web pages are no longer active but they have been retained on

the WayBack Machine.

For those who may be interested the pages are located here:

Black Powder Menu

Black Powder History

Black Powder Recipe

Black Powder Charcoal

Black Powder Saltpeter

Black Powder Sulfur

Homemade Black Powder

Black Powder Handgonne

Shooting the Handgonne

Forging a Handgonne

Black Powder Proving Mortar

Oldest Swiss Handgonnes

Making a Slow Match

Shooting the Japanese Tantsuzu Gonne

Most web browsers provide the ability to save web pages

and some enable saving as pdf files too. I'd recommend

saving the pages for future reference. They're really some

of the best found anywhere.

February 10, 2020

Sea Monkey, hi,

Bretscher has compiled an interesting collection of observations and opinions here, but this is by no means an all-encompassing fully-comprehensive compendium on BP science. And the guy would benefit from investing in a ball mill. For example, in the video from "Homemade Black Powder" he compares open burn rates of a gram of some commercial Swiss BP vs his best (I'm guessing) homemade batch, using his hot willow charcoal with components mixed using a mortar & pestle, wetted and riced. The commercial Swiss BP (3Fg, I believe) burns just like my usual milled/riced 75/15/10 willow BP, i.e., almost like a slightly sluggish flash powder. His homemade powder is a comparative embarrassment (for pyro purposes, at least), and burns like my screen-mixed components if I don't bother to pre-mill any of the components beyond 40-60 mesh--the stuff's perhaps good enough for gerbs and stars, but I'd deem it worthless for rockets and burst, and you'd need a whole lot of it for serviceable lift. So, instead of compiling "just about everything we need to know about BP", I would instead suggest that the guy has a strong interest in BP (apparently for firearm use) and has dug up and organized some interesting though limited-in-depth and scope historical and chemical information on BP, but he himself still has quite a lot to learn, particularly with respect to hot BP characteristics necessary for pyro, and how to (easily) achieve them. Certainly not with his mortar & pestle to make "golfball" sized batches. But thank you for providing the links--they are interesting, for sure. Including the gentleman's claim that BP was first invented in Europe (in "Black Powder Handgonne").

To JV above, the empirical formula for charcoal after pyrolysis is generally given as C₇H₄0, which would have a molecular mass of 104, of which carbon would comprise 80.7%. This is towards the top end of Shimizu's 70-80% carbon that you mentioned. Almost certainly, this ratio varies by tree or plant species. Wood is primarily composed of the complex carbohydrates cellulose and lignin, and water. Of course there are other minor constituents, including the volatiles that are native and new ones that are formed during pyrolysis. I'm sure most of us who retort charcoal have at some point noticed leakage of tarry materials and the buildup of tar/creosote/etc inside the can. These are the volatiles that have not burned off but have condensed after vaporization, and include a host of polycyclic aromatic hydrocarbon compounds amongst many others. Most of these compounds are not chems that we would select to use as a primary fuel for BP-like materials. Some of these are the chems that give smoke the smoky smell and flavor (look at the first ingredient in Liquid Smoke), but like related asphalt are not necessarily the best fuels for our desired pyro end result. By cooking these off, most of them at least, we are better able to take advantage of the charcoal's porous nature, likely making these pores more accessible, which allows better infiltration of the oxidizer (and sulfur) into the fuel. Milling makes all of these particles smaller and additionally promotes better integration. Brief wetting additionally facilitates this tight incorporation.

The gentleman that until last year operated the reputable customcharcoal.com (website now defunct) used to specifically inquire of the customer whether the Alder coal he sold was meant for cooking or pyro purposes--if it was for pyro, he would cook it a little longer to remove more of the aromatics that we much appreciate for imparting flavor to grilled foods (and it also burned longer before becoming cold useless ash), but which inhibit BP burn rate. So, the gentleman Bretscher's assertion that charcoal for barbeque/grilling has been "burned to death" and is not suitable for BP is, to me, not necessarily correct. Reversed in logic, actually. His assertion that pyrolysis temperature can change the nature of charcoal is correct--there's always going to be a very small fraction of remaining volatiles, but we probably never reach the temperatures and cooking times in typical retorting that would cause this to be a major consideration in the final BP burn characteristics, at least not that I've noticed across several different retort batches of the exact same wood, harvested and treated the exact same way at the exact same time, but cooked at different times and varying temperatures. So, in my view, overcooked charcoal means burned charcoal, aka ash, which is good for little. Undercooked charcoal is suboptimal for making fast BP because the "volatiles" and other remnant chems are not great fuels for our needs (most of them, at least) and possibly clog the charcoal's pores from nitrate entry. All said, the chemical reactions and intermediate and final products of BP combustion are complex, and burn rate may indeed benefit from the presence of some of the remnant chemicals beyond carbon alone. These, like porosity, are probably highly variable across different woods, and to my knowledge remain to be well characterized. While you can always slow down fast BP, it is much more difficult for the most part speed up crummy BP if you've made it as good as that charcoal will allow.

Dissenting opinions and experiences are always welcome, preferably with data or supporting evidence.

Edited February 10, 2020 by SharkWhisperer

February 10, 2020

In years of trying to learn more about charcoal and it’s place in black powder as we’d use it in pyrotechnics I find the information is very limited. There are tons of papers and research information on biochar and BP for ballistic purposes though.

What my simple mind has taken away from all the things I’ve found so far is that volatilities are needed in some degree. A good example of this would be to try using activated charcoal in BP. As far as I am aware this seems to produce poor results in BP.

All fields that discuss charcoal in great detail seem to get into cooking methods and when the research gets in-depth start to venture into heats and times of cooking. Time more so in bio char though.

I don’t believe we have a great wealth of information on charcoal as we would use it. I don’t believe there is a great wealth of BP research on BP as we’d use it either. If we do have such I’ve not found it yet. We do have some decent information, but not any detailed research. One the best resources I come across in modern days was exiting the public arena as I entered the art. I did manage a few emails with the gentleman, but his health was declining by this time. I would assume much of his knowledge may have fallen under a non disclosure agreement though so he often referenced research from US military papers from jet propulsion laboratories. Those research papers seemed to reference past research of others quite often. I almost get the impression from the references that they were taken as gospel and independent testing was Not done to confirm the results. I’m not bashing those fellows just stating a curiosity.

I’ve only ever stumbled across one reference to cooking temps for charcoal for fireworks that I can recall and it seems different from that of BP for ballistic purposes. I found that interesting.

Have I found everything ever written about charcoal and BP? I would think and hope not. I think I’m more of a curious beginner on the subject. I’m definitely not highly educated with degrees on the wall or such mess. Am I curious, certainly!

I’ve wanted to do a research project for a few years now, but have hit the road blocks of time and figuring out some test methods I would like to do. As I think it would be fun to make a comprehensive test of various variables into charcoal as it relates to BP for our uses. When I finally figure out the remaining methods for the tests I want to do they’ll be made public some how.

I personally think we are doing ourselves a disservice thinking we have enough of charcoals relationship to BP figured out. Is that a real bad thing probably not. Most people learn to make BP that serves there purposes and move on into other parts of the art. If you can make consistent BP that is serviceable for your own needs then you’ve accomplished a goal as a Pyro. Are JV’s abilities to make better BP than my own absolutely ( we are friends so I know this to be true ). Do we collaborate on the subject fairly often along with other subjects. Have we learned things from each other I would like to think so. Do we always agree, not as often as we should, lol.

So to the original poster my suggestion would be work towards a serviceable charcoal for your own purposes. The fastest and hottest charcoal isn’t always the best or necessary. Best example of that comes from the fact that once the hobby field started ball milling BP we quickly exceeded the performance of many of the commercially available BP’s on the market. And millions of fireworks are made each year using commercially available BP’s. Many of the older more accomplished builders in the art choose to purchase their BP I assume to dedicate more time to building than processing BP.

If you are a BP rocket header then hotter BP’s may be your goal.

February 10, 2020

As a curiosity, I searched the charcoal pore size. I found that it is in the order of nano meters (https://www.sciencedirect.com/science/article/pii/S2213879X16300190), much smaller than the powders used for BP. So is it possible that potassium nitrate and sulphur enter these pores? Maybe only after dissolving them with isopropyl alcohol and water.

PS: I`m attaching a video with the eucalyptus BP

February 10, 2020

BP should ignite with a woof, almost like flashpowder.

Charcoal made for cooking has volatiles which WILL oxidize with atmospheric 02 when milled fine enough. The volatiles make charcoal pyrophoric. This is not a myth, I've had it happen to me. As a result I will not use cooking charcoal for pyro uses.

The conditions which favor such a reaction are rare and otherwise difficult to purposefully achieve but I've seen enough to understand the possible dangers. I don't cook all the volatiles from the charcoal but do cook most out and consider this an absolute necessity to make good hot stable BP.

February 10, 2020

JJ, your BP burns faster than I'd expect for lump eucalyptus charcoal, particularly given that you have might not be quite at optimal milling conditions yet. It's definitely fast enough for many applications as is. I expect that increasing your mill media volume and time will speed it up even further. So congratuations, you're on your way.

The paper you cite details production of activated charcoal by heat and/or phosphoric acid treatment, which act by additionally removing remnant volatiles, i.e., "due to the facilitation of volatile matter release, The acid acts as a dehydrating agent that inhibits tar formation, which characteristically clogs the mesopores and micropores." Whereas they are referring to macropores as those with a radius >50 nm (one thousand nm per um), and micropores/mesopores as even smaller, it is also important to remember that wood charcoal also contains larger macrostructures, including pores, that are remnants of the tubular transport systems (e.g., xylem and phloem) present in plants for moving water and nutrients through the plant tissue. And other structural macrocomponents such as gaps between growth rings, etc.

Note that their extreme heat (600C) and/or phosphoric acid treatment followed by heat-drying causes the starting charcoal to lose approximately 20-30% of additional mass; this is the remnant volatiles (and probably other acid-soluble heat-stable compounds too). Yes, it's hard to fathom things on the nanometer scale (and angstroms, an order of magnitude less than nanometers), but they clearly show that enhancing microporosity at this level increases absorptive capacity for the bacteria E. Coli, which is an organism with more familiar dimensions (i.e., micrometers, um). These little rod-shaped critters are typically around 1 um in linear dimension, which is similar to the size of a proportion of particles in decent pyro Al (e.g., 2 um).

What pore-size ranges of charcoal are most critical for BP integration? It's easy to envision the importance of both micropores and larger macropores; the effects of water and milling on BP speed suggest both are important. There are plenty of scanning electron micrographs of charcoal available; It would be really cool to see electron micrographs of BP after milling!

In any event, your BP is definitely getting there, using the charcoal you had on hand. I'm pretty sure you can speed it up even more by optimizing your milling conditions. NJ's video above shows the burn rate of what I'd agree to be typically hot, high-quality pyro BP, and approximately what you should be aiming for. But your current BP is probably sufficient for multiple applications.

What's next, and what first pyro projects, beyond BP manufacture/testing/optimization, do you have in mind? Anyways, it looks like you're off to a very good start, and thinking things through along the way.

Edited February 10, 2020 by SharkWhisperer

February 10, 2020

There was a challenge some time back on FW. The goal was to make serviceable lift with airfloat charcoal, which is 'known' to be no good for BP. I was able to tease enough performance out of the charcoal to achieve the goal. Along the way, I experimented with mesquite charcoal. The barbecue charcoal was run through a garbage disposer to break it down, and then milled for 6 hours with SS media. I'm an advocate of screen-mixed black powder, so I was eager to see what could be done with charcoal that has been deemed 'unsuitable' for black powder.

I used my own hot water method to prepare the powder for granulation. The powder had an additional 2% dextrin as binder. Part of the challenge was to have "durable" grains. I was able to get a 7.5 second baseball flight time (approximately 300 feet apogee) with 14 grams of my final powder. This is 'about' the performance one would expect from Goex (2FA?). I tried 75-15-10 and 70-20-10 base formulas. The 70-20-10 result is the one I reported here, derived as an average from 3 flights.

I've long believed that the fineness of the charcoal component is a major factor in BP performance. Others have investigated alternate charcoal ratios, which I incorporated into my mesquite experiment. Milling efficiency is pretty important, IMO. Large media don't mill charcoal as well as small media. Small mill jars with less 'fall' don't mill as efficiently as larger jars with the same media.

Based on my limited experiences with 'crappy' BP charcoals, I recommended 70-20-10 as a simple adjustment the OP could make to improve black powder made with less than ideal charcoal. My main concerns with using barbecue charcoals for BP would be abrasive materials (rocks, sand), moisture, and uneven cooking. Some pieces will be undercooked, while others may be cooked to the point that they develop a graphitic structure.

The black powder papers linked to on Wichitabuggywhip are excellent.

February 10, 2020

Hey JV, nice results with "crappy" charcoal, for sure. Although you may be correct that moving to 70/20/10 could further enhance burn rate--it might or it might not--I think the OP should continue with his base recipe to finesse the most he can out of his milling technique with the formulation he's been consistently using to date before tossing in another variable. It's likely given his description that his mill is undercharged with media, that his milling times for that size unit might not be long enough to have reached a point of diminishing returns, and it remains uncertain if he has completely dried his powder (and consistently between batches) after granulation/ricing. Those parameters, once verified as optimal for his equipment and chems would then allow him to directly compare his "best" 75% to his "best" 70%. To switch over now might be premature--it could easily be, particularly given that he's using a different wood than you've tested, that 70% KNO₃ will not, unlike your experience with mesquite and hardwood airfloat, be an improvement over his current 75% with eucalyptus. It might be faster, and it might not be, but he'll never be able to tease apart this with any certainty until he can standardize his manufacturing techniques and do a valid side-by-side comparison.

In my hands, using ERC and willow charcoal, and standardized production methods, I get a small but perceptible decrease in speed by dropping nitrate to 70%, incrementally and linearly slower at 65%, and slow as a dog (but great for core burners!) at 60%. I am not alone with these observations, though everybody's methods, and charcoal, differs to some extent--I am definitely not questioning your results. Let's let JJ nail down his best production technique and standardize it, so future formulation comparisons are valid. To switch formulas now would be effectively starting over--no matter the outcome or how small/large the differences, he will still have to go retrograde and compare it to his original formulation to be certain of the best mix with his charcoal.

February 10, 2020

Pyromaniac,

Yes, Bretscher wrote his materials principally for those who are interested

in making their own Black Powder for shooting purposes. While his

writings are not fully comprehensive they do encourage all who are

interested to experiment with making their own. As most of us are aware,

once bitten by the Black Powder Bug, our searches for new info on the

art of making it are never-ending.

On another forum years ago on the subject of really fast Black Powder one

member discussed how Charcoal made from ordinary newspaper worked

superbly. In addition to verifying that possibility I'm going to test charcoals

made from junk mail advertisements and also cardboard.

Attached is a booklet which to me is quite interesting.

Swiss-Black-Powder-Booklet.pdf

February 10, 2020

The local paper mills use mostly oak pulp. From my testing with red oak this claim does not surprise me. I found red oak to make wonderfully hot BP. The oak charcoal was difficult to mill but not impossible. A quick blending in the blade mill before adding it with the other chems to ball mill breaks up the larger, harder chunks.

I'm uncertain what effects the ink would have so I'd stay away from printed paper and the glossy paper, it is usually impregnated with some form of plastic.

Edited February 10, 2020 by NeighborJ

February 11, 2020

In addition to verifying that possibility I'm going to test charcoals
made from junk mail advertisements and also cardboard.

lol... please let us informed

BP should ignite with a woof, almost like flashpowder.

Charcoal made for cooking has volatiles which WILL oxidize with atmospheric 02 when milled fine enough. The volatiles make charcoal pyrophoric. This is not a myth, I've had it happen to me. As a result I will not use cooking charcoal for pyro uses.

The conditions which favor such a reaction are rare and otherwise difficult to purposefully achieve but I've seen enough to understand the possible dangers. I don't cook all the volatiles from the charcoal but do cook most out and consider this an absolute necessity to make good hot stable BP.

about the video: that's what i`m trying to do. Do you guys recommend wet milling?

It would be really cool to see electron micrographs of BP after milling!

What's next, and what first pyro projects, beyond BP manufacture/testing/optimization, do you have in mind? Anyways, it looks like you're off to a very good start, and thinking things through along the way.

agreed. It would be nice to see a study using electron microscope of milled BP.

after defining a good optimized method to produce BP I would like to make a mortar. We can buy mortars here in brazil, but I think I could make my own and for a lower cost.

Pyromaniac,

Yes, Bretscher wrote his materials principally for those who are interested
in making their own Black Powder for shooting purposes. While his
writings are not fully comprehensive they do encourage all who are
interested to experiment with making their own. As most of us are aware,
once bitten by the Black Powder Bug, our searches for new info on the
art of making it are never-ending.

On another forum years ago on the subject of really fast Black Powder one
member discussed how Charcoal made from ordinary newspaper worked
superbly. In addition to verifying that possibility I'm going to test charcoals
made from junk mail advertisements and also cardboard.

Attached is a booklet which to me is quite interesting.

It is written in this paper that they remove the bark from the wood. Does anybody here use the bark to make BP charcoal?

Tomorrow I will finish another burn speed test and I will post the results here.

Edited February 11, 2020 by jimjones

February 11, 2020

I'm pretty sure that everyone removes the bark before cooking their charcoal. It is recommended that only small branches be used because the growth rings are wider. Those fast growing parts of the tree make the fastest BP.

Wet milling is a process generally only used for paints and pharmaceutical applications because it can easily mill chems to sub-micron particle size. I've not heard of any other pyro using this process. It does work amazingly well. It does not come without its drawbacks. The charcoal does require extra steps to dry it before weighing and dry milling into the other chems. During the charcoal drying process it is necessary to monitor the charcoal for exothermic oxidation reaction, it is very similar to milling aluminum and this is when I experienced that phenomenon. Once it is completely dry it can be assumed that any oxidation which could happen already has. For the sake of safety I don't recommend trying it, dry milling works just fine.

February 11, 2020

Everybody I know strips the bark off before making charcoal.

My willow coal comes from branches no greater than 3-4"" (8-10 cm) in diameter, mostly smaller.

Wet milling seems like an unnecessary headache in this instance; a bigger problem is guaranteeing that your BP is actually dry! I seriously doubt that a few hours in a breeze at 77F has removed all the water that will evaporate. I cannot more strongly emphasize that a longer drying time is almost certainly necessary, and faster drying, perhaps in the sun, with occasional rotation/turning? I can guarantee that your BP will burn much faster if it is completely dry.

Some have said newspaper makes decent charcoal; some say it sucks ass. I have no opinion, or interest in exploring this personally. Actually, I've got a pile of dried tomato stems (super porous) that I thought I'd retort and make BP with for my amusement (one of these days--low on the list).

Add more marbles, mill longer (marbles are low-density vs typical milling media), and make sure your BP is dry, dry, dry. BP granules can easily fool you and flow freely like powder while still containing a lot of water that you do not want.

If you're almost, but not quite, happy with your BP and charcoal then you can consider re-retorting your charcoal over a fire/coals in a coffee or paint can for 15-20 minutes and see if volatiles are still coming off (they will burn, if asked). If so, this might speed things up a little, it might not. Don't overdo it and turn it to white ash.

If you are using lump charcoal (not compressed briquettes) then I wouldn't worry about the possibility of rock or sand (or binder) contamination being too much of an issue.

You are almost there, meu amigo!

Re mortars, smaller ones can be rolled with good kraft paper without difficulty. There is plenty of advice available for making your own mortar (and rocket--similar process) tubes. Good tube bottom plugs are very important. Start small if you do not have a local mentor, and continue asking a lot of questions--do not guess. Maybe make a star gun or launch a few smallish comets and mines. To get a taste of how your powder works as lift (your grains are pretty small if going through an 18-mesh screen first). DO NOT consider using common PVC plumbing/conduit tubing for mortars unless you have a death wish. Most of us purchase fiberglass or HDPE plastic; steel in some instances. Paper works well up to a certain size and won't send off the shrapnel that other materials will if you have an explosion. No mortar lasts forever--pay attention to wear, distortion, and burn-through.

Maybe make a few gerbs/fountains, before moving on. Learn to make blackmatch--you will be using a lot and it is very easy to do. You will need a lot of reliable fuse. Your current BP would probably make very decent blackmatch.

But first of all, JJ, get your milling optimized and really dry out your stankin' damp BP, hah ha!!!

February 11, 2020

The 600C ( 1112F for us crazy Americans ) temp is closer to inline with the Swiss pdf file posted I believe is the singular reference I’ve found cooking at those temps. Many of the military papers I was pointed towards and searched out recommended a cooler temp 426c ( 800F ) if my memory serves me correctly. The Swiss paper should elude to the same citing the different temps between ballistic powders and fireworks if that’s the reference I recall.

I’ve tinkered a little on a prototype TLUD to eventually hopefully find the answer to temps and volatilities. The below video is a preliminary proof of concept test. The next TLUD will be adjustable to try to regulate the temps better. OldGuy has a thread here abouts some where on a retort I liked the design of that addressed some issues I feel may be present in normally practiced retort cooking. Although they are just suspicions currently I don’t know if I’ll venture to the realm of retort testing or not in length to find out.

https://youtu.be/FbFOPeDgUSs

JV, oddly enough if what I think is see in the OP’s video is correct he may need to switch the ratio in the opposite direction than either of us anticipated just a smidge.

There are almost to many variables in play with charcoals and the average Pyro screen granulating BP methods for most of us to compare research to great degrees. I’ve spent many hours discussing and debating ideas with JV to try to find some more consistent tests. The current tests are fine for functional use, but if you wanna compare apples to apples better options need to be figured out in my simple opinion.

NJ, knows me well enough from the other forum to know part of my comments are speculation as they are written in such a way to imply just that. I don’t claim to be any authority on the subject by any means. I’ve just researched the topics extensively to learn more about the subject myself and try to share some of what I’ve found to save others the extensive research.

I do believe there are many things left for us to learn about charcoals and BP.

Richard has a density test of charcoal he can use to anticipate the performance of the resulting BP it is used in that as far as I am aware has proven pretty accurate for him.

JV and I came up with a puck pressing concept for repeatability that hasn’t been blown out of the water yet unless Richards tests creep a flaw in it. Why press a puck to a pressure when weight of material and volume of the puck are used to determine the density. Build your tooling to accommodate the results and fill to that and press with any force that bottoms the ram out on what JV coined as a Tophat. Richard’s density info may creep in there a little at some point though. We’ve not gotten that far.

Plus the huge bonus the active discussion may lead to more interesting info. I’m sure there are many, many more research articles I’ve not stumbled across someone else has that may arise and toss something else into the mix. I know of a couple of people who have done some testing of there own, but am not aware of any written results in any public domain.