usapyro Posted October 9, 2012 Posted October 9, 2012 My standard technique for drying KNO3 for BP and other use is to take it and blend it with +1% pine charcoal until it starts to cake up inside the bullet blender and refuses to blend any more... Then I add it to a sealed jar with Dry-Z-Air desiccant prills. The prills are sealed inside paper towel balls with rubber bands holding the paper towel balls full of desiccant closed. I have never had great results baking KNO3 dry. The crystals seem to lock in moisture or something and when it's blended it will eventually start to cake up again inside the blender which means it cannot be completely dry! Or maybe it is dry and KNO3 just has a tendency to cake when it's really fine and stops blending? The bullet blender I am using can blend 150g of a chemical to dust within a few minutes provided it doesn't cake... What techniques do you guys use? Maybe I need to bake the blended stuff at like 300F for five hours or something?
spitfire Posted October 9, 2012 Posted October 9, 2012 Almost pure KNO3 does cake a lot. I have a barrel with 99,98% pure, very fine KNO3 powder and it asks for screening. Even worse, it tends to form hard lumps. I'm not familiar with grinding the fresh crystals, but the result should be somewhat the same. It might be the nature of this material, and nothing to worry about. In the past i used fertilizer grade KNO3 small as table salt. I baked this in a cooking pan, and weighted before and after cooking. The result was a 3% loss of weight of a total of 150g. This gave a more free flowing powder, easier to work with. But, it doesn't matter at all for the final result of the BP. The Charcoal and the ballmill where the most critical steps.
Mumbles Posted October 9, 2012 Posted October 9, 2012 I had similar issues with nitrate. Even after drying to a constant weight in the oven, and cooling in a dessicated environment, it would cake when ground. It seems like the little crystals just like locking together. I'm sure cabosil would help. I've heard some people talking about putting the chemicals into a slow cooker overnight to dry them. That doesn't actually seem like a terrible idea. The nitrate does cake as it dries. When using it in the oven, I would take it out every 30 minutes and break up all the clumps to make things go faster. It took about 2hr at 300 or 350 to dry out about 7lbs of nitrate. In my experience, the charcoal was just as problematic, if not more so, than the nitrate. Storing it in an airtight environment with a desiccant is going to be the way to do it though, especially if it's stored in a non-climate controlled area.
pyroshell Posted October 9, 2012 Posted October 9, 2012 That is how I store all of my hygroscopic chems. I use lye desiccants for most of them, I put them in an airtight containers.
usapyro Posted October 9, 2012 Author Posted October 9, 2012 In my experience, the charcoal was just as problematic, if not more so, than the nitrate. That is interesting... I didn't know that charcoal attracted moisture. It's probably pretty hard to tell if charcoal has any moisture in it. I shall toss a desiccant into my airfloat charcoal from now on too! Anyone know if sulfur needs a desiccant?
Col Posted October 9, 2012 Posted October 9, 2012 (edited) I always dry my kno3 and charcoal prior to milling, 90 minutes in the slow cooker on the high setting is just right.Charcoal is definitely worse than kno3 for absorbing moisture, i`d dry it first then use the desissicant to prevent it picking up moisture. If its already damp, you`ll need a lot of dessicant to dry it out Sulphur doesnt seem to be an issue, mine is in a airtight hdpe jar so that may be the reason but i`ve never bothered to dry it. Edited October 9, 2012 by Col
psyco_1322 Posted October 10, 2012 Posted October 10, 2012 Why is everyone so worried about your chemicals have a little atmospheric moisture in them? The only thing I actually dry before using is Strontium Nitrate.
ExplosiveCoek Posted October 10, 2012 Posted October 10, 2012 Why dry chemicals at first, to just wet them afterwards? Doesn't seem really logical to me.
Col Posted October 10, 2012 Posted October 10, 2012 If the charcoal or kno3 is damp, it will spend a good percentage of the mill run stuck to the walls of the jar instead of being ground by the media. 1
dan999ification Posted October 10, 2012 Posted October 10, 2012 (edited) im coming round to the idea myself now, the willow must have some water in it since the retort is sealed with a damp cloth, does it actually soak up atmospheric oxygen aswell? It does get stuck to the jar but since i only mill 3 hours and check on it, break it up etc i find no problem really, funny thing is the balsa made in the same way stays as powder and wont clump no matter how long i mill it, does the oily nature of balsa charcoal prevent it from absorbing water? I can see the importance of having dry chems in some circumstances nitrates/al being one, i also think that dry chems would be benificial if you were to store meal powder, it would probably grow mould. Dan. Edited October 10, 2012 by dan999ification
Col Posted October 10, 2012 Posted October 10, 2012 (edited) I dry my lead media every now and then just as a precaution, dumping it the slow cooker for a couple of hours is no great hardship. I dried 185g of fairly old willow charcoal (stored double bagged in a dry location) and it lost 10g in the process (2 teaspoons of water) so the moisture content was around 5.4%. If your charcoal and kno3 are damp, it will throw your bp ratio`s due to the weight difference. If i didnt dry the willow i`d have about 6g of charcoal missing from the batch when it went into the mill. With a large capacity mill (kilo`s at a time) it could make a significant difference Edited October 10, 2012 by Col
spitfire Posted October 10, 2012 Posted October 10, 2012 Very interesting. I never knew, or wondered, whether charcoal had a tendency to collect moist. Based on the findings of Col it's worth testing for me. The weight difference might be important. Considering the effect of using different ratio's for BP. I never had any problems with caking in my mill though... it always runs as a free flowing powder. We've got a scientific way to solve this: ask yourself a question, bring up a theory, test the theory in practice. If the theory is not confirmed by the tests, alter the theory. In the end we have scientific proof. Nice project!
Algenco Posted October 10, 2012 Posted October 10, 2012 when moisture is a problem charcoal is nearly always the culprit.doubtful it would have enough moisture to throw the ratios off enough to notice unless is was very wet
Mia Posted October 10, 2012 Posted October 10, 2012 I dry my lead media every now and then just as a precaution, dumping it the slow cooker for a couple of hours is no great hardship. I dried 185g of fairly old willow charcoal (stored double bagged in a dry location) and it lost 10g in the process (2 teaspoons of water) so the moisture content was around 5.4%. If your charcoal and kno3 are damp, it will throw your bp ratio`s due to the weight difference. If i didnt dry the willow i`d have about 6g of charcoal missing from the batch when it went into the mill. With a large capacity mill (kilo`s at a time) it could make a significant difference Nice edit
dan999ification Posted October 10, 2012 Posted October 10, 2012 well 5 or so percent explains the difference to me, my willow is obviously prone to absorbing or has absorbed more water than my balsa, prepared and stored in the same way one cakes one does not, one i thought was fast......balsa you get the idea.However some charcoal requires less oxidiser some more, regardless of clumping this im sure can affect things even on a small scalle ratio wise using different wood and water contents, your mileage may vary.Off to the charcoal/bp tables. Dan.
Col Posted October 10, 2012 Posted October 10, 2012 I think its important to try to control the variables for the sake of consistancy. A slight shift in the ratio combined with a drop in milling efficiency due to early clumping could make a noticeable difference to the performance of rocket fuel. Its not like you can do much once its pressed into the tube
dan999ification Posted October 10, 2012 Posted October 10, 2012 right you are, never thought really since not many are bothered, if you check and film your powders you will see but might not be able to work out why unless you consider the variables. This is another moving of the goal posts to me. Dan.
AirCowPeacock Posted October 11, 2012 Posted October 11, 2012 I always dry my charcoal, KNO3 and even sulfur (for the heck of it) before milling black powder. Normally my KNO3 is chunky. But after a week in my dessicator (w/ Calcium chloride & Magnessium sulfate) its fine and free flowing. It takes a long time to penetrate the moisture in deepths of the clumps. I also put my 3 lb rubber mill jar w/ allumina media in for about a day. Its a long process--but otherwise I notice issues with clumping to the walls...resulting in poor powder and damage to my media.
Dragonflightpyro Posted August 9, 2015 Posted August 9, 2015 Hi,I'm using all Skylighter chems straight out of the box, and I'm getting very bad clumping while ball milling. It would all clump up very hard at one end of the container and was difficult to break up. I did break it up several times, but it's quite annoying to have to go check it every half hour. Is this indicative of wet chemicals? I did a trough burn rate test, but I used the freshly milled dust. I didn't granulate it. I couldn't find any tables to compare ungranulated dust, but mine burned 2.5ft in almost exactly 2 seconds. It seems horribly slow compared to the tests athttp://www.wichitabuggywhip.com/fireworks/charcoal_tests.html but all those were riced or granulated. I do plan to do a test with my granulated stuff, but I'm more concerned about the clumping in the ball mill and what that means. Thanks.Alex
Mumbles Posted August 9, 2015 Posted August 9, 2015 Hi Alex. It does sound like at least one of your chemicals is wet. Nitrate and charcoal are the usual suspects. I've personally never had a problem with airfloat charcoal, which is all Skylighter sells, but that doesn't mean that it can't be the culprit. You may want to try to weigh out some nitrate, and dry it in an oven for a bit. Weighing it after it dries will tell you how wet it is. It's amazing how much of a difference a few percent cam make. Once dry, storing the chemicals with desiccant packs can help keep them that way. Over time it could also help to dry things out. A different charcoal will help with the speed. It's difficult to get a high performing black powder out of commercial airfloat.
Dragonflightpyro Posted August 10, 2015 Posted August 10, 2015 (edited) Hi Alex. It does sound like at least one of your chemicals is wet. Nitrate and charcoal are the usual suspects. I've personally never had a problem with airfloat charcoal, which is all Skylighter sells, but that doesn't mean that it can't be the culprit. You may want to try to weigh out some nitrate, and dry it in an oven for a bit. Weighing it after it dries will tell you how wet it is. It's amazing how much of a difference a few percent cam make. Once dry, storing the chemicals with desiccant packs can help keep them that way. Over time it could also help to dry things out. A different charcoal will help with the speed. It's difficult to get a high performing black powder out of commercial airfloat. Thanks Mumbles. I did dry my charcoal and nitrate. The results were as follows: KNO3 13.0 oz ---> 12.45 oz. Airfloat charcoal 15.47 oz ---> 14.95 oz. That was following three hours in a slow cooker on low. Do those sound like numbers I should be concerned with? Is that enough moisture to cause the clumping? That's around 4-5% moisture in both of them. Edit: Also should I screen the chemicals together than seal them up with some desiccant to dry them all out at once before milling? Edited August 10, 2015 by Dragonflightpyro
Mumbles Posted August 10, 2015 Posted August 10, 2015 I had a similar amount of water in my nitrate. I never tried to dry my charcoal, so I'm not sure there. I suspect things will be better if you try to make a batch with the dried materials. Drying out a screened batch before charging your mill sounds like a good idea to me as well. Once you figure out a process, you'll be in great shape I suspect.
Oinikis Posted August 11, 2015 Posted August 11, 2015 (edited) Thanks Mumbles. I did dry my charcoal and nitrate. The results were as follows: KNO3 13.0 oz ---> 12.45 oz. Airfloat charcoal 15.47 oz ---> 14.95 oz. That was following three hours in a slow cooker on low. Do those sound like numbers I should be concerned with? Is that enough moisture to cause the clumping? That's around 4-5% moisture in both of them. Edit: Also should I screen the chemicals together than seal them up with some desiccant to dry them all out at once before milling?I've read somewhere that if BP contains 2% of moisture, it's considered wet, so I think 4-5% should be concerning. As Mumbles said, try a batch with the dry stuff, and see the difference. Edited August 11, 2015 by Oinikis
insutama Posted August 11, 2015 Posted August 11, 2015 i think alot of it is on were you live i live in a very dry climate and i have never had to dry any of my chemicals i just keep them in a airtight container with silca packs and i have never had any issues with weak powder.
tradami Posted August 12, 2015 Posted August 12, 2015 Just for reference to people regarding this topic. I recently milled some BP using red alder charcoal. I milled 640 grams for an hour in an optimized mill using a rebel 17 drum and 35 lbs of media. When I opened it after an hour this is what I got. Please keep in mind that moisture is not the only factor in clumping. Temperatures can cause clumping as well. When I opened my milling box everything was hot inside from sitting under the sun. I believe that in combination with a little moisture caused this. http://puu.sh/jsXzf/8b096c205d.jpg http://puu.sh/jsXDN/15b53eaf55.jpg http://puu.sh/jsXKt/78c2942775.jpg
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