Trying for consistent lift powder.

[Merlin]

I have made several batches of meal powder testing the burn speed after each run. I stop milling when the burn rate is less than one half second for 3 grams meal-d spread in a crease made diagonally in typing paper. I then granulated to 2FA dextrin bound BP screened and seperated from 4A and fines . I then combined all of the 2FA BP and mixed well so I could consistently use the same charge for given shell weight. I do this because I am not consistent batch to batch in the final product- so I am taking an average.

Even so, having tested several samples with a 3 inch mortar and baseball the results are poor with my granulated 2FA.

 

It takes 33grams of the 2FA to send a baseball to 400 feet. I also made MCRH for burst in the same way. So I decided to try a charge of MRCH to compare. 25grams of the MRCH (1:7) sent the baseball into orbit. (over 900 ft actually). Does anyone have any idea why? The granulated FA2 and the MCRH were made of the same meal powders. I am at a total loss. Any suggestions welcome. Getting consistent BP has got to be the most difficult aspect of pryo! I am tempted to toss 10 lbs of granulated bp!

Edited December 12, 2015 by Merlin

[MadMat]

I have been fairly accurate and consistent with my lift, but before I can give you any suggestions, I have one question. I seem to have a mental block when it comes to acronyms, what the hell is MRCH?

[lloyd]

Merlin,
I really have to ask a 'basic' question. Did you make the meal-coated rice hulls from the SAME batch as you'd granulated to 2FA size?

It makes no sense that screen-granulated powder (which is porous and faster than corned powder) would be slower than coated hulls made from the SAME batch!

Also, just to "pick a nit" -- mill dust is NOT "meal powder". It's mill dust. Meal powder is the 'fines' left over from classifying pressed-and-corned BP.

 

Lloyd (duplicated)

[Wiley]

I'd be willing to bet that your powder isn't dry. Are you using a drying box or are you relying on the elements to dry your powder?

[Merlin]

Sorry MadMat- MCRH not MRCH-- a typo. Meal Coated Rice Hulls

 

I have been fairly accurate and consistent with my lift, but before I can give you any suggestions, I have one question. I seem to have a mental block when it comes to acronyms, what the hell is MRCH?

[Merlin]

I use a drying box and dry at 135 degrees with flow through air for 24 hours. It may still not be dry or could have picked up moisture but it has been in the same environment as the coated rice hulls. However. I have found one mistake. I have gone back and measured the actual particle size of the granulated bp and according to the chart it is not 2FA but 1FA individual grains being up to 8mm. Could this be the reason it is slow?

 

I'd be willing to bet that your powder isn't dry. Are you using a drying box or are you relying on the elements to dry your powder?

Edited December 12, 2015 by Merlin

[Merlin]

Merlin,

I really have to ask a 'basic' question. Did you make the meal-coated rice hulls from the SAME batch as you'd granulated to 2FA size?

 

It makes no sense that screen-granulated powder (which is porous and faster than corned powder) would be slower than coated hulls made from the SAME batch!

 

Also, just to "pick a nit" -- mill dust is NOT "meal powder". It's mill dust. Meal powder is the 'fines' left over from classifying pressed-and-corned BP.

 

Lloyd (duplicated)

Is this the same Lloyd as on passfire? If so, ignore my post on passfire it is the same. I made several batches of meal-d but tested each batch for burn rate. I made the coated rice hulls from multiple batches of meal-d in a cement mixer. I then granulated the remaining batches of meal-d into what I thought was 2FA and dried each batch. I then combined all of batches into one well mixed lot of 10 lbs and seperated that into 2 lb bags for storage so regardless of which bag I use it would all be the same.

One thing I have found in measuring the individual grains of BP is that according to the charts it is not 2FA but 1FA with grains running 5 to 8 millimeters. Should I try to crush it and re-screen it to 2FA?

[MadMat]

I thought about it for a while and I'm not surprised with the better performance of the coated rice hulls. the rice hulls would give you a more consistent shape to the individual grains. Also, because of the curved shape of a rice hull, there is more surface area than a solid BP grain of the same size. This would result in a faster burn rate. I may be wrong, but it makes sense to me Another thought, if there is remaining moisture involved, The rice hulls would more than likely be drier. I have noticed that coated rice hulls dry much faster than solid BP grains

Edited December 12, 2015 by MadMat

[lloyd]

I don't buy any of it. IF it's 2FA size, it's about the same size as the hulls, and porous as heck due to screen granulation. It should burn about the same.

 

That you say it's really 1FA size (which is a HUGE difference) makes some sense.

The granules will take longer to dry completely than do the hulls.

 

(yep, same person)

Lloyd

[MadMat]

Opps! I kinda glossed over the fact it was screen granulated, yeah my idea wasnt the greatest, but the moisture thing holds. Yeah, the size difference between 1FA and 2FA would make a big difference!

Edited December 12, 2015 by MadMat

[Merlin]

Well, lacking the sun I have placed a closed zip lock bag in the drying box to see if any moisture collects- may take a while. It is not hot enough to burst the bag. I appreciate all the advice given.

Given that the end product is really 1FA would it be worth the effort to crush it and re-screen and dry? The screens I have are the cheap green plastic ones you see on amazon and ebay and they are not labeled so its possible I granulated with too large a mesh - but the micrometer doesnt lie.

[schroedinger]

Merlin yes 1FA is way to big to lift 3". What you want here is 5 FA. I will bet that you will use only about 20 -25 g of 5 FA to send your shells to the right height. MCRH have only about 1 mm coating of bp on them, which will burn up 4 times faster then an 8 mm granule (burns from two sides).

[schroedinger]

Also for testing your powder use a mortar and not a line of meal-d. The reason for this is that a line of bp burns with a lot of variance in burn time according to the temperature of the meal.

[FlaMtnBkr]

I guess I don't see it actually spelled out except for the word granulated. You are screen granulating and not pressing and corning correct? What size screen are you using and are you pushing it thru or using more of a grating motion? 8 mm is pretty big chunks and there is a lot more thickness to burn thru compared to a coated rice hull, even if it's a bit porous from screen granulating.

 

I would imagine the large size is the biggest difference between the two.

 

What charcoal are you using out of curiosity? If making your own it should be fairly easy to make screen granulated powder that is faster than commercial powder. I also agree that you should use a baseball, dummy shell, or a BP tester that FPAG has detailed and the instructions are on Skylighter. Then you will know exactly what it will do when lifting something. I don't think there is enough information on how burn speed on paper correlates to lift strength. Unless you have done extensive testing and are sure in your test.

 

You also might want to figure out your process a bit better before making 10# of BP. There shouldn't be much variation between batches and if it's that noticeable try to track down the reason unless you aren't milling the same amount of time or to the point you have determined it's done and doesn't change significantly with further milling.

 

If you are using good charcoal and have a good mill/media then it should just take a bit of practice and then you will be able to make great BP without thinking about it.

[Merlin]

It is probably the size and or moisture. I only use the burn test on paper to get an idea of when the milling is done. I use the baseball mortar shot to determine performance of the finished BP.

You are correct I should not have made 10 lbs without baseball tests. As for charcoal I use what I have available which was alder, willow and red cedar all of which are supposed to be good charcoals. I intend to use red cedar or white pine as those are most available locally but I have 9 lbs of willow still left. I used a screen with 1/4 inch openings which is about 3 mesh I think which I incorrectly thought was right for 2FA and use a pushing and grating motion when granulating. Looks like I will have to get another screen.

[Merlin]

Merlin yes 1FA is way to big to lift 3". What you want here is 5 FA. I will bet that you will use only about 20 -25 g of 5 FA to send your shells to the right height. MCRH have only about 1 mm coating of bp on them, which will burn up 4 times faster then an 8 mm granule (burns from two sides).

One thing I picked up along the way was that you need good flame propagation so you dont want your powder granules packed too closely. At the same time I can see if the particles are too large the lift power would be reduced. I thought 4FA was too small granulation to use let alone 5A. I read that 2FA was the size to lift round shells and I applied it to all shells up to 4 inches. Guess I was wrong on particle size and the mesh size to produce 2FA so ended up with 1FA. A lesson that will not be forgotten.

[Merlin]

This is where I got the idea that 2FA is 1/4 inch granules. None passed the 12 mesh screen but the #4 screen results in particle up to 1/4 inch in size. So if it passes a #4 screen I though the granules were 2FA even if most were around 1/4 inch.

 

“Recall that the mill dust has 1% dextrin in it to act as a binder. To granulate the mill dust, we will be adding very hot water to it to activate the dextrin binder. We will then create a ball of "putty," and granulate that putty "grating" it through a wire-mesh screen.

The screen we will be using to granulate the BP is a 4-mesh Skylighter screen, which has openings that measure approximately 1/4-inch square. So, our resulting granules will be about 1/4-inch and smaller in size. Smaller granules will burn faster and more powerfully, but it's difficult to nicely granulate BP through a screen much smaller than the 4-mesh one. If we want smaller granules, it'll be easy to break the large granules into smaller ones once the BP has been granulated and dried.

If the powder is sifted in the 12-mesh screen, and the particles finer than the 12-mesh openings are removed and set aside for other uses, then the BP that remains in the screen would be referred to as "-4+12-mesh" (minus four, plus twelve mesh). This means that all the granules would pass through a 4-mesh screen, but would be retained on a 12-mesh screen.

 

That size range, -4+12, is the particle size range of grade 2FA commercial black powder.”

[lloyd]

(sigh...)

In one breath you say it's 1FA-sized, and in another you're trying to defend that it's 2FA-sized.

 

Which was it?

 

Lloyd

[Merlin]

I dont mean to be defending myself just explaining why I was confused. The majority of granules were 5 to 6 mm while some were 8 mm because I suppose some granules stuck together during drying. Some granules are in the lower 2FA range but most is in the 1FA. I plan to try per skylighters instructions to break it up and dry it again.

1FA 8.0-4.0

2FA 4.76-1.68 If this is correct it looks like 1FA can be as small as 4mm and also 2FA can be as large as 4.76mm resulting in an overlap of particle size between 1FA and 2FA.

 

Whatever grade it is it must be not dry or too large for small shells.

 

I screened the dried granules through a 1/4 inch screen and kept what was on the 12 mesh.

I think I should screen through a 12 mesh and keep what is caught on the 20 mesh. 4FA ?

Edited December 13, 2015 by Merlin

[Arthur]

Yes there is an overlap between mesh sizes and F sizes.

 

First test for particle size, then test for dryness. If it passes one sieve then rests on the next -that's it's size. Weigh some powder then dry it some more then weigh it again -look for weight change. FA and 2FA will not dry quickly though they may surface harden.

[FlaMtnBkr]

Lloyd, he did say what size they were; 5-8 mm. He then said why he originally thought it was 2FA which is reasonable. No reason to get exasperated.

 

Merlin, something that can make a big difference is how long the BP takes to dry. The rice hulls likely had less water to begin with and could also dry a lot quicker with a thinner BP thickness. The longer the BP stays wet, the greater the likelihood of the nitrate dissolving and then growing in bigger crystals that you worked hard to reduce.

 

I granulate my BP onto plastic trays that can't absorb water and shoot for layers 1/4"-3/8" thick. I place the trays in the sun and if it's cloudy I will even put a fan on them but well away from anything in case it decides to turn into a fire breathing dragon. After an hour or so and once the top starts to dry out I stir the granules to get wet material to the top. If you do this 2 or 3 times on a nice sunny day you should have crunchy hard granules in 2 or 3 hours and drying this quick really maximizes power. I've had hot powder that ended up taking closer to a day to dry and it was just ok after that long compared to powder made the same way but dried quickly.

 

Just something else to think about.

[Merlin]

Thanks for your reply. I was confused about the size. Skylighter says use a no4 screen but I must be over wetting because some of the granules are oblong the length being in the 8mm range and I am piling it too thick so some granules stick together. I broke up some last night to re-dry but I think thought if it's still slow the nitrate may have crystallized. I guess I could re-mill it and regranulate maybe. Since it has dextrin any moisture would cause it to clump. I put a bag sealed in the drying chamber and saw no sign of moisture after several hours. Like I said I broke some up much finer and dried. The current weather won't allow a test today but when I do if it is still weak then it's a sure bet the nitrate crystallized out.

[lloyd]

Not exasperated, just waiting for "the final answer" <G>.

 

This last sort-of indicates they might be "whaling powder" size, even larger than 1FA.

 

Heh! It's easier than your experiences have indicated, Merlin. You'll get there.

 

LLoyd

[Merlin]

OK this is what I have found so far. Yes the granules are much too large some 2A some 1A and everywhere between. My fault. Maybe a little overwetting or maybe pushing some through #4 screen resulting in elongated granules. I crushed a small amount and screened it. I did a test and the lift was improved 16%. I believe not only were the particle sizes too large but I layered too much on the drying screen to dry. I confirmed no moisture was present in the final product but very likely due to the long drying time I had nitrate crystallization. I can use the stuff to lift my shells by using larger amounts for lift but I have question. If I were to re-mill it, re-wet and granulate to the correct size and dry a thin layer would it be possible to reclaim it? I have a hydraulic press so I can corn the bp- just never tried it. But since the pressed pucks would have much less moisture the drying should be more efficient without nitrate crystallization much less. Bottom line should I crush the 10 lbs screen it and make due or since I have all the time in the world would it be advisable to re-mill it start over. I hate to waste chemicals. Thanks. Lesson learned.

Lloyd I know you are a great guy. I sing your praises on all the forums. I use you method of shell construction on plastic ball shells.

[lloyd]

If I were to re-mill it, re-wet and granulate to the correct size and dry a thin layer would it be possible to reclaim it? I have a hydraulic press so I can corn the bp- just never tried it. But since the pressed pucks would have much less moisture the drying should be more efficient without nitrate crystallization much less. Bottom line should I crush the 10 lbs screen it and make due or since I have all the time in the world would it be advisable to re-mill it start over.

------------

IN order:

1) Yes. There's nothing in there except any dextrin that will suffer from multiple tries. The dex is probably good for 3 attempts before you'd have to add a little more.

2) I press and corn with NO added moisture. If powder is pressed to the correct density, it requires absolutely no added moisture, other than that water of crystallization in the nitrate.

3) You won't hurt a thing by using the powder as-is, and just using more. Re-processing it is your choice. Were I you, I'd crush it up a little more to about 10-20 mesh (polverone), and use it for shell-filler (not 'burst' per se), and start fresh. You won't waste anything, and you'll be working from "known conditions".

 

Lloyd