BP Grades and how they effect burn rates?

[SignalKanboom]

Is mill powder supposed burn slow? I dont understand wether grading mill powder is to speed it up, or if my powder is too slow. I did a small burn test and it seemed very slow. My charcoal was red cedar pet bedding and I milled it at 65 rpm for 1.5 hours. My ratio was 75-15-10 and my media was 5lbs of 1/2 inch lead balls. Edited September 27, 2020 by SignalKanboom

[Arthur]

Fully incorporated powder does burn slowly, when it's pressed and corned or granulated it burns faster. You need to make a fully finished powder before you can properly test it.

Make a batch and mill it for what time you expect, then open the mill and take a sample then mill again for say half an hour, take a sample again and repeat. Then finish off each sample ans check for speed. There will be a time where further milling yields no benefit, that's how you check how good your mill routine is.

 

Likely the sample would be 20 ish grams and the test would be to launch and time a baseball.

 

There is the option to re-mill powder to look for improvement, there is also the opportunity to call reject powder "fountain mix".

 

Having optimised your mill routine, you can then make batches using different woods, to see the effect. Only with a good mill routine will you get repeatedly good powder which is essential for good fireworking.

[Carbon796]

What kind/brand of mill are you using ?

[SharkWhisperer]

Forgot the exact specs of your mill but if you're using a HF-similar barrel (4" diameter, 6" length), half-full of .50" lead balls at 90 rpm with no slippage or clumping, in my experience, you're not going to get max burn rate until 8-12 hrs of milling, using ERC charcoal (not over/under cooked) and that standard formula. When I spun at those speeds, I wouldn't even look at it until 4 hours, and that was just when I needed to solve clumping issues. Typically just left it alone all day or all night...

 

Even before granulating (or corning if that's your preference--not mine), that concoction should burn in a pile on untreated writing paper and barely leave char marks--definitely not burn holes or a lot of residue. Once granulated, it'll burn noticeably faster.

 

Likely under-milling. Easy test & easy fix. Charcoal quality next.

[SignalKanboom]

Fully incorporated as in corning and grading? I thought burn tests could be done straight out of the mill. Good to know it burns slower as powder.

 

I built my ball mill and there is no slippage. I checked the rpm of the mill and it ran consistently every time I checked the speed. The mill has variable speed control and I can speed it up, or slow it down. I thought 60 rpm was good for a jar the size of mine. My jar is 4 inch diameter and 5.5 inches long. I have read a lot that milling can be done in much shorter time than people say, but I havent double checked that with anyone here. Milling makes me nervous because I dont have a completely remote location to mill, but I do have a enclosure that would stop any kind of accident. My jar is constructed with burst disk, so that pressure cannot build high enough to create extreme pressures. It is a sponenburgh jar, but instead of hard caps glued on the end I used rubber caps and used a Rtv gasket maker to make sure the jar could not leak. It was liquid and air test for leaks.

Edited September 28, 2020 by SignalKanboom

[SharkWhisperer]

Mill it longer, speed it up a bit. Half full of lead balls + comp atop, between balls and only reaching 75% full, max. BP rarely blows during smart milling. Or not many of us would remain. Not so interested in your sealing-- 1) It's sealed, right? Good. 2) IF (so unlikely) it ever were to blow, are you going to potentially hurt people or cause a residential fire? No? Good start. A jar that size can only mill 150g BP (total weight of all ingredients) reliably, pushing it is 175 g. You will likely notice an obvious problem if you try >200g (plus, it'll be almost full of ERC bedding charcoal cuz it's super not-dense). You're fine. Try a 150g batch. Turn up the speed to 90 rpm (many tutorials on here about milling parameters), and enjoy.

 

Yes, your mill powder will always be faster after granulating (simples) or corning (meh, don't bother). On a subjective 1-10 scale of burn rate, I get an extra 1-1.5 points after granulating mill dust (usually starts at again, a subjective, 8/10 burn rate) so my final BP rates (my scale) 8.5-9 of a possible 10 in burn speed. It's always equivalent or more usually faster than commercial Goex BP of the same granule size. I use 70% isopropyl alcoholto granulate lift/burst powders that contain dextrin (remaining 30% is water to dissolve binder for hard granules) and 91% isopropyl for rocket fuel because it dries that much faster than pure water. Water is good, too, and cheap. But I don't like to wait forever for BP to dry, so use alcohol for granulating.

 

Try longer/faster/lower volume milling first. Then consider your charcoal. Making badass BP is half art/half smarts. Not difficult unless you have kaka charcoal (you're new, no? is possible you over/under cooked your ERC and have no way of knowing). But I bet it's your milling conditions.

 

By the way, ERC, if from bedding wood chips, generally does not need pre-milling because the stuff's pretty small/fine to start with. I would avoid that unecessary extra messy step like the plague. Meh!

 

And you only need a gram or two of BP to do an open-air burn test; larger amounts are for testing your promising powder in actually launching projectiles, after granulation.

 

You'll get it.

[SignalKanboom]

Thanks again shark! Your posts make me feel better. My burst disk rubber cap idea isnt going to last. I ran at 100 rpm and the jar started walking so I set up a jar stop and it began pulling my caps off from the opposing forces acting against the jar.

 

I have realized I am being way too cautious and I need to just make a regular sponenburgh jar, or buy a professional jar. The powder burnt faster than any homemade YouTube bp I have seen, however guys with pyro in their name that have granulated their bp, or seem to know what they are doing have exceptionally fast bp (pooofff) mine is more Like (ppffffhooofff). I did make my charcoal and it did have some ash in it (overcooked), but I did not mill it separately before. I figured it would be Milled down just the same all together.

[Mumbles]

92rpm is optimal for your jar and media size. For future reference the formula to calculate that is 265 / sqrt(Jar ID - media diameter. That will give the critical mill rpm, which is when balls start to stick to the walls due to centripetal force. Typically we use about 65% of that to get an optimal rpm. The 265 approximate. There's a small fractional component of it, but I can't seem to find the real value right now, but it wont change the number much.

 

I think speeding your mill up will be the improvement you needed. I wouldn't worry about internet mill times. There's a lot of people who I think try to humble brag about that and probably over exaggerate it. Take some samples along the way, but you'll probably find 3-4hr is the sweet spot. Longer probably will improve it more, but at a certain point there will be diminishing returns.

 

I definitely wouldn't call well milled meal powder slow. When you have good powder and it's well milled, it will probably burn in an instant. You don't need much to test. A small pile, probably less than a gram. I use the same test SharkWisperer mentioned with the paper. Really good powder will leave very little residue and not really char the paper at all.

 

Good luck. It sounds like you're on the right track.

[Bourbon]

I always found that people looking for BP that burns like flash, are looking for bragging rights. In fact, in many cases from what allot of the elders say, can lead to failure depending on the application. A good thump or whomp that burns nice and clean on paper, open air, is just fine.

[SharkWhisperer]

When have you ever heard somebody complain that their BP is just too damned fast?

 

It's easier to slow down fast BP and impossible to speed it up without adding additional non-BP chems. There is such a thing as too slow for many applications. There is not such a thing as too fast, because it can always be tempered. Making very fast BP is easy with decent wood/charcoal. I tend to think people who are satisfied with mediocre BP or have crappy charcoal and make slow-ass endburners (that probably wouldn't even budge my finned hybrid rockets off the pad), wimpy core-burners, and learn to live with their handicap instead of eliminating it. "Just increase the lift charge volume 50%" is an absolute waste of chems and demonstrates complacency with a yet-to-be-optimized skill set or a perpetually crummy source/manufacture of charcoal.

 

SignalK, you're well on your way to success. Increase milling speed/time and it might be the only answer that you need. Time is easy. Speed--you were suboptimal and your jar was getting compromised at higher speeds. Until you buy/build a new reliable mill, then increase the speed from 60 rpm, as far as you can go before you start having friction problems. With suboptimal speeds, lengthened milling can partially help things. What's the rush? An hour or two total mill time would be great, can be achieved with larger mills, but is simply not enough for hobbyist mill sizes. Yours is very close to the HF design--I ran those for many years befroe upgrading, and the still see occasional use for small-volumes, and they work. But they're just slower than pro mills. Around $50 for dual-tumbler with ubiquitous 20% off coupon and you're spinning. Do you truly need larger at this point? But it's really no big loss if you need to let your current unit (reliably and safely) run all night, is it?

 

If you seriously overcooked your charcoal (pic?) then that, too is an easy fix. With ashy charcoal, your BP would be fuel lean (not as much actual burnable fuel per volume as you calculated); how much depends on how much ash (non-fuel) is present. If it's just a few pieces or the top layer with ashy edges, but the stuff in the center is solid black, you're probably ok. Remaking a batch is easy enough. Pack it tight, use only 1-2 nail holes if retorting in a coffee can, and cover them up with a wet rag to minimize oxygen entry while cooling. IF this contributed to your problem, your first batch is not useless. Don't toss it. By trial and error, you might increase charcoal percentage (so you have desired value, thouugh some carryover ash) that could be functional.

 

Also, if it turns out that you charcoal really got a charring and has lots of ash, still don't toss it. It could be very useful for ground effects/gerbs/fountains, slower-burning star comps, primes, making fuse/blackmatch. Plus, if you wet granulate your first batch with or without trying to repair it, it WILL speed up the burn rate. If you don't add dextrin/binder, you can easily resize granules to any size you want. Think of it as an alternative to slower-burning commercial hardwood airfloat that you now don't need to buy. Probably not a major loss. Tis an inexpensive (apart from time) learning experience.

 

You'll get it, I have no doubt.

[SignalKanboom]

I made my charcoal with the tlud method. Could it be i overcooked it?

[Carbon796]

It's most likely fine. Try not to over think stuff, until your actually doing stuff " correctly/traditionally/by the book ". Just being in the ballpark isn't close enough sometimes. You have to pay attention to the correct details.

 

Your mill is just too slow, and your mill times too short. For what is optimal, for your size mill.

 

Your mill is 33% too slow, and your mill times are probably off by 50% or more, as a minimum. That equals slow BP. Get the milling right, then you can overthink the stuff that doesn't need over thinking.

 

Also watch out for the 75% mill jar full description. It's not really an accurate representation. By total physical volume the mill will only be slightly over half full. Because the 25% fill of chems, will fill into all of the 50% media fill intricacies. Even though the media fill is 50% the media is not a solid mass.

Edited September 28, 2020 by Carbon796

[Bourbon]

I've heard it several times. Thus, I said it. Depending on application is correct. Fast BP "is" what you want. Just don't spend all your time trying to make flash out of BP unless that's what you're into.

Edited September 28, 2020 by Bourbon

[BetICouldMake1]

I'm with Bourbon. If you build large cylinder shells your BP can be too hot to use for lift. To some extent you control this with particle size, but even still there are limits. It's easier to make BP of the quality you need than it is to mess around with trying to temper it with additives. It seems every batch of BP I make is bigger than the last and disappears faster. I want the production process as simple as possible. You need BP good enough for your needs, what those are varies but the need for it to be crazy fast is rare. You also need to balance ease/speed of production with end quality. Running the mill for an extra hour to save a 1/2oz lift isn't worth it to me at the rate I go through powder.

[SharkWhisperer]

I made my charcoal with the tlud method. Could it be i overcooked it?

Tis possible, but as many have stated, fix the obvious, clearly-defined issue (suboptimal milling conditions) first. The final (milling-optimized) product might easily be acceptable to you without further tinkering. And it will definitely get even faster after wet granulation and sizing, and reducing back to powder if you wish (new dust still will outperform pre-granulated milling-only dust).

 

If improved milling doesn't solve the burn-rate problem to your satisfaction, then you've eliminated that variable as the problem, and have a pretty good idea what to consider tinkering with next. Once you've standardized your process (including charcoal wood source and cooking conditions), and are happy with the end product, then you're golden and can expect consistently good BP batches from then on. And if you end up doing small-batch BP manufacture for the time being, you can balance the slight batch-to-batch variation that might occur simply by pooling them together, whether according to granule size or as BP mill dust batches before granulating.

 

Curious what first projects you intend to undertake (rockets, shells, fountains, etc...)? A decent set of screens is likely next on the list after you've got your mill all set. Ultimately, you'll probably have quite a collection of different mesh screens, but probably 90% of my screening for BP/star & core sizing and screen mixing some comps uses 4, 8. 10, 20 and 40-mesh screens. My 60 barely gets any use, and my 100-mesh is only occasionally used. My 1/2" (2-mesh) doesn't get much use either. Many kitchen implements such as pasta and cous-cous strainers and dollar-store bacon grease-catching screens often are repurposed for pyro. Cheap as chips but make sure they're plastic or stainless steel (other metals have sparking risks or will get eaten up by your chems).

 

So...what's first on the project list once you've got your BP sorted out?

[SignalKanboom]

Well my first project will be lifting a dummy shell I will construct. It will break, but no effects will be put into the shell. This is to get my spollette and shell spiking construction down. I have a set of 304 stainless screens I framed. I may put a simple charcoal effect of choice into the shell. I havent decided yet.

 

I have no desire for a very fast powder, but I can tell my powder is too slow and burns very dirty. When I mention my charcoal as a potential problem it is not because I wont take the advice about adjusting my milling procedures. Everyones advice is received loud and clear. Charcoal air exposure was simply a question I had in the process of making my charcoal when I noticed air exposure creating ash.

Edited September 29, 2020 by SignalKanboom

[Richtee]

I still say try newsprint. Pack that retort tight.

[SignalKanboom]

I still say try newsprint. Pack that retort tight.

What will the newspaper accomplish?

[Richtee]

Cook it like wood. Use it for charcoal. Fastest stuff I ever made. It was pressed and corned however. There’s a vid of it here somewhere. Err...wait...found it on YT

 

https://youtu.be/4w4MpHLAQA4

Edited September 29, 2020 by Richtee

[Arthur]

I had a mate who used a (variant) TLUD process in a 50 gal drum. He always sieved on a 600 mesh before using it. What passed was wood ash (largely potassium oxide>hydroxide>carbonate) and white, what sat on 600 mesh was ace charcoal.

[Richtee]

I had a mate who used a (variant) TLUD process in a 50 gal drum. He always sieved on a 600 mesh before using it. What passed was wood ash (largely potassium oxide>hydroxide>carbonate) and white, what sat on 600 mesh was ace charcoal.

Interesting method that. Huh.

[SignalKanboom]

Cook it like wood. Use it for charcoal. Fastest stuff I ever made. It was pressed and corned however. Theres a vid of it here somewhere. Err...wait...found it on YT

 

https://youtu.be/4w4MpHLAQA4

Holy cow, thats fast. I dont need super fast powder; Just lift and break powder, not launch and vaporize powder.

[Richtee]

Holy cow, thats fast. I dont need super fast powder; Just lift and break powder, not launch and vaporize powder.

Eh... I seem to recall only needing 15 grams or so to well launch a 3”. You adjust. As mentioned, it’s easy to slow down if needed.

 

try the newsprint.

[SignalKanboom]

Eh... I seem to recall only needing 15 grams or so to well launch a 3. You adjust. As mentioned, its easy to slow down if needed.

 

try the newsprint.

I was trying to be funny more than anything. Everyone is always telling me my powder doesnt need to be fast. Problem is I have 2lbs if fireworks cookbook air float that is supposedly cedar and paulownia. I also made a pound of red cedar pet bedding charcoal.

 

Can you really get enough charcoal from newsprint? How much do you need?

[Richtee]

Can you really get enough charcoal from newsprint? How much do you need?

Pack your retort tight, as I said. Use a axe handle or whatever to pound it in. It’s been over 10 years, but I seem to recall getting 50 or so grams out a paint can.

 

Just added it in the ball mill as flake. it’ll be airfloat in a short time in there.

Edited September 30, 2020 by Richtee