How does KNO3 behave on drying and heating?

[ChrisPer]

I have been trying to get my ball mill working but so far all I get is caked balls and pellets.

I start with a blade grinder, just KNO3 and a 100 mesh screen. Ball mill is 6" diameter (150x150mm), half full of .690 (17.5mm) musket balls.

 

I tried a drying box over a 60W bulb. No useful effect, more pellets after 4 hours tumble.

I tried a drying box with a 150W bulb. No happiness, more pellets after 4 hours tumble.

 

 

My KNO3 is now yellow-brown.

 

I added a fan heater on low through a tunnel into the drying box. It seems to be drying OK, exhaust air is mildly warm to the hand.

 

But does KNO3 have bound water in its crystals? Is it broken down by the heat I have applied? How can I tell if its dry enough BEFORE its run in the mill?

[MikeL]

Drying box - small ceramic space heater. Example: https://www.amazon.com/gp/product/B08C5GYMCW/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

 

Ball mill speed is important (I don't have a specific speed, I'm very new at all this)

Musket balls are soft lead and that isn't going to last. The lead goes somewhere and doesn't do much good for the composition

I tried milling just KNO3 once. I don't do that anymore.

[ChrisPer]

Yes, ceramic space heater is a very good suggestion noted from earlier posts. I made a tunnel with a gap from the fan heater to the tunnel, and only individual ingredients in the dryer.

 

Trying to make dry air, not hot air, and the gap and tunnel are to allow sparks to expire before entering the drying box.

 

My balls are a personal problem, and if I get a successful batch made will upgrade.

 

I liked the 'filled copper pipe' idea, but someone reports they corrode horribly; maybe a galvanic corrosion problem.

At present I plan to go to wheelweights instead of soft flashing lead, and bore out a Lee .577 minie mold to cast cylinder media.

 

Anyone got any information about the KNO3 behaviour - free moisture, is there moisture of crystallisation that needs a higher temperature, and does the KNO3 degrade at drying or oven temperatures?

Edited March 9, 2021 by ChrisPer

[Bourbon]

Did you clean your musket balls before their first use? Much of the ball ammo you can buy is greased and soft. I wouldn't mention it, but you say your KNO3 is "yellow-brown." It should be greyish if anything.

 

The first time I used lead ammo, I milled cat litter 2 times at 4 hours each to clean them. I'm sure there are better ways to degrease them, that's just what I did. Later I switched to hardened lead, specific for milling (Woody's for quality), so they didn't come with grease.

 

https://www.woodysrocks.com/store/p79/5lb_Lead_Ball_Mill_Media_.html#/

[ChrisPer]

Did you clean your musket balls before their first use? Much of the ball ammo you can buy is greased and soft. I wouldn't mention it, but you say your KNO3 is "yellow-brown." It should be greyish if anything.

 

Good ask!

I cast these suckers new myself, from scrap roof flashing, and they were clean when I started. I was very pleased to get the .690 mold secondhand for the job.

 

You made me think. I think the colour comes from my first attempted batch of meal powder (garden charcoal, was very poor result) coating the balls. I washed and rubbed them before the KNO3-only batch, but the KNO3 took the colour of the coating on the balls.

Edited March 9, 2021 by ChrisPer

[SharkWhisperer]

KNO₃ is mildly hygroscopic; it'll absorb perhaps 2-3% of its weight in water. Easily cooked off in an oven at lowest setting (if gas, you're making water--crack it open or get it hot, turn it off, then put the nitrate in). It is not flammable by itself. Most water/clumping issues w/BP are because your charcoal has a lot of water in it. Charcoal can absorb 20% weight in water (my measurements) though others say more. THAT's what causes clumping in mills, ffs. Dry it out in a hot oven--it doesn't take long. Your life will improve immediately.

 

Discolored KNO₃ would concern me if if wasn't attributed to turning grey from your lead milling media (which wouldn't concern me, though I wouldn't make a habit out of sniffing it). "Garden" charcoal? Sheesh. You're behind the lines on that one.... "Garden" charcoal? Friggin' cook yourself up some hot-ass charcoal. REAL charcoal. Frlm the large collection of decent BP woods. It's the #1 cause of puss powder, ffs. Besides mortar/pestle mixing. That's just dumb. There's MANY threads on making decent charcoal. Your "garden" charcoal just won't cut it. But I'm happy to sell you some Kingsford Briquette! They're the bomb! No, they're not....

Edited March 9, 2021 by SharkWhisperer

[ChrisPer]

Thanks!

I have in fact since the first batch made myself Willow charcoal by collecting deadfall branchlet kindling from under willows in nearby parks. Its all been macerated in the blade grinder until it passed through the 100 mesh screen. Got more willow collected, and also about 10kg of paulownia wood.

Edited March 9, 2021 by ChrisPer

[Arthur]

Clumping in a mill IS CAUSED by damp ingredients. Sulphur contains negligible moisture, nitre contains little, but charcoal can contain 50 to 100% moisture and still look OK. For a ball mill the mix needs to be dry so put the charcoal in a dryer for a while first.

 

Put each ingredient in a snap top sandwich bag and just leave them on the table for a while, the moisture usually show on the inside of the bag as condensation.

 

Put an open jar of each ingredient in a lidded bucket and also put a big, dried, silica gel pack in there, leave it for a few days, try not to contaminate the silica gel bag with ingredient dust.

 

Weighing powders with different moisture content leads to some really bad powder batches.

[Mumbles]

You have to get potassium nitrate pretty hot to decompose it. By pretty hot I mean approaching or exceeding 1000F. It's not a long term solution, but drying a single batch of nitrate before milling in an oven at about 250-300F has worked for me in the past. It's more of a way to figure out what's going on, rather than a fix for all your nitrate. Drying a bunch would get tiresome and probably irritate the owner of the oven. While not particularly toxic or bad for you, I still like to keep my cooking and pyro separate. Another thing to look at is possibly putting the lead media in the drying tunnel. Sometimes they can have surface water.

 

I've always been less than enthusiastic about the idea that a drying chamber, that maybe hits 100-115F, has any real effect on drying chemicals. I'm unconvinced that that low of a temperature provides any real effectiveness of providing any true water removal. It will dry out surfaces, and at least seems to make some people feel better. It's also better than nothing.

 

If the ultimate goal is to produce BP, you may want to consider adding in a little bit of charcoal with the nitrate. It's going in anyway, and charcoal can act as a pretty effective anti-cake. A common ratio is to mix 75 parts potassium nitrate with 5 parts charcoal. This mixture is non-flammable by all accounts I've read, so issues with milling in less than ideal areas are less of a concern. This is ultimately mixed with a 1:1 blend of milled charcoal:sulfur to get to the final BP ratios. This has been a common way to make BP of decent quality for those not willing to risk milling the complete mixture.

[ronmoper76]

yeah i would agree with what they said. From large chunks right into the ball mill for 3-6 hours and i'm looking at a super fine powder within 6-12 hours and its so fluffy that its not far from airfloat. You must have moisture somewhere,sodium benzoate is the only one that cakes for me no matter how dry it is when you get it super fine. i get a lot of my chemicals in big chunks and always have to mill it down to the mesh i need. i had to do 10lbs of barium nitrate yesterday,and barium sulfate right before that. I have yet to have anything that was wet,or wouldn't break down,i have milled different metals also and it doesn't matter how hard they are 7 days in a mill and it's down to dust,you can ball mill practically anything that isn't dangerous and that will fit in your jarand it is gonna keep getting smaller and pretty damn fast. I have a green house fan that blows air any direction and i just place pans,stars,whatever under it,if i have something crazy wet,then i put a induction heater with a pot of water under the pan along with the fan still blowing. There is nothing i have made yet that wouldn't dry overnight except super large batches of benz or sali fuel,it takes about 24 hours to get all the naptha smell out of a large pile of whistle fuel,that shit lingers,usually. a double boiler set up under a fan is super fast,SAFE, and it doesn't have to cost anything if you already have the fan,that's my two cents.

Edited March 9, 2021 by ronmoper76