my charcoal

[pyrochris732]

Hello,

 

So I ground down my willow charcoal that I got from customcharcoal.com using baseball bat and then a coffee grinder, and then 5 hours in the harbor freight. It came out really nice and soft but I also noticed that it clumped together very easily, as if there was some moisture in it. I didnt introduce any moisture with milling it.

 

Will this affect how it gets balled milled with the sulfur and KNO3?

 

Could the humidity have played a part in the moisture?

 

This batch will be used for coated hulls and stars. Im just worried that there will be an issue in how it mills as black powder. Im leaving it in the crappy tumbler for 24 hours.

 

Thanks,

 

Chris

[Mumbles]

You know, I wonder the same thing. BP clumps quickly in my kilo sized jar. Quick enough to not mill everything. By the time it clumped in my harbor freight mill it was done though. If you're worried, just open and break up any clumps every few hours.

 

A similar mix (spider formula) made with commercial airfloat milled like a champ with no clumping what so ever. This does use about double the amount of charcoal though. Maybe I'll take some into the lab and bake some to find out.

[Twotails]

I have found some charcoals take a certin % water if left open after cooling.

 

Willow was cooked, 500g charcoal still warm. left open to cool overnight(normaly i close it for a day or two)

 

Next morning willow charcoal was cold. bagged it and set it in the workshop.

 

Small amount of condensation was observed in the bag as the day heated up.

 

Charcoal was weighed again. Weight of charcoal was about 515g or so. Thats 3% water gained overnight.

 

Im baking another batch, its realy humid tonight, i'll see if the results compaire.

[jwitt]

Here's two recommendations. OK OK three.

 

First- you can test your charcoal by sealing a bit in a bag and sitting it in the sun. Condensation = too wet.

 

Second- even if it passes that test, my SOP is to dry charcoal before milling. Cookie sheet + foil + oven at or just under 200°F. Gently stir at 15 minutes and you'll find it sticks to a metal spoon like glue. Well, like moist powder. Stir again at 30 minutes and you'll see a bit of airfloat floating in the air. Give it another 15 minutes and it should be good to go. Now, since you're smart and used that foil, pick up the two long ends and bring 'em together- the charcoal is in a line running longways down the foil. Kind of roll the top up a bit and the tube you've made fits nicely in a big freezer ziplock.

 

I process about 1 pound of charcoal mill feed this way- stuff about 30 mesh down to airfloat. Seems to work like a charm.

 

Third- I've heard that BP will inevitably clump in your mill when it's done. This may be due to heat build-up, may be due to the slight bit of moisture still in the mill feed, or might be due to the finely divided particles really liking each other? Anyway, my last several mill runs that result in "good" BP (relatively speaking, still need almost 25% of shell weight to lift super high) have all clumped into a huge ball in the center of my grinding media. It's crazy looking. Might not happen in a small mill- mine's a 6" PVC jar.

 

Additional info- So here's my "Is this good BP" test. Burn some mill dust. If there's no slag left behind (little droplets of KNO3 that precipitate out of the mix when it burns) then it's good to go. This is just from my observations- might or might not hold true, but it will tell you if your BP is mixed well enough at least. It's possible that the mixture could be milled longer and improved.

 

Another thing I've pondered, and will look into is whether the clumped "finished" mill dust can be dumped out, broken up, and re-milled to improve it. We shall see- I'm thinking that once that clumping has taken place, it's to the point of diminishing returns. I'll be doing more BP "research" after I have my shells built for the 4th and I can monkey around a bit. I mean- it's friggin' black powder...pretty fun science experiments I'd also like to make a bit of sporting powder for myself and a few reenactor friends who might appreciate a handmade pressed and corned product.

 

On the note of improving BP, I'm happy with mine, even though a lot is required to lift a shell, so I'm gonna be making gradual changes. It burns pretty cleanly and leaves no visible slag. Also, I guess a slower burning powder provides a nice "gentle push" to the shell instead of slamming it, although the thunderous cannon shot last weekend is hard to think of as gentle. But it's a matter of degrees.

[dagabu]

Charcoal is hygroscopic, it picks up moisture readily from the air and will stay there until it evaporates or is driven off. Dont worry about the moisture unless you cant mill the BP or you are using it in a comp that doesn't use water.

 

If the humidity is below 60%, a fan with a light breeze will dry the charcoal to an acceptable level. You are doing fine.

[Ventsi]

I have a theory that its not the "charcoal" thats hygroscopic, its the salts that are within it[think ash] and they absorb the water, Carbon wick it off the molecules and it slowly continues...

Or it might be me just being crazy

[Mumbles]

It could be, but that doesn't make sense why good willow charcoal (~4% ash) would soak up a bunch of water, while shitty commercial hardwood airfloat(10-20% ash) is bone dry all the time.

[Arthur]

Urbanski mentions the different properties associated with the different temperatures of charcoal manufacture. In reality, summarised, charcoal yield goes down with increasing cooking temperature, while powder power goes UP with temp, but sensitivity goes down as temp goes up.

 

SO for a high yield of sensitive powder and for simple process convenience the charcoal we usually get is charred at about 300C. However at this temp the charcoal is still hygroscopic and powder made with it will be hygroscopic too.

 

If you have charcoal that absorbs moisture it will need drying before milling, and the powder you make may also be hygroscopic.

 

Read a respected text and realise that charcoal is the ingredient giving most variables to the powder, wood type and charcoaling temperature matter a lot. Davis states that good powder will be in equilibrium with atmosphere with about 1 - 1.5% moisture, but if this gets past 3% then performance may be impaired.

[pyrochris732]

Well guys.. I went to check on my charcoal after 24 hours today and when I opened the lid all I saw was my media. I was like, "where the hell is the black powder?!" So i dug down and found a ball (tennis ball size) of what must be the black powder, solid as a rock. It had a shiny super hard surface and litterally looked like a large stone. I guess I did need to dry out my stuff before milling, lol.

 

I grabbed a hammer and it split right open. I actually did a little burn test on one of the particles and the stuff burns fast as hell still! Im going to put it back in the mill for awhile though just to be safe so that i know it works.

 

Bizarre.

[dagabu]

Well guys.. I went to check on my charcoal after 24 hours today and when I opened the lid all I saw was my media. I was like, "where the hell is the black powder?!" So i dug down and found a ball (tennis ball size) of what must be the black powder, solid as a rock. It had a shiny super hard surface and litterally looked like a large stone. I guess I did need to dry out my stuff before milling, lol.

 

I grabbed a hammer and it split right open. I actually did a little burn test on one of the particles and the stuff burns fast as hell still! Im going to put it back in the mill for awhile though just to be safe so that i know it works.

 

Bizarre.

 

Yup, it almost always will ball up if left long enough even with dry ingredients. Several batches this winter that I made when relative humidity was 20% still balled up. I found that I needed to thump the jar on the ground once every half hour to keep it fluid.

[pyrochris732]

Yup, it almost always will ball up if left long enough even with dry ingredients. Several batches this winter that I made when relative humidity was 20% still balled up. I found that I needed to thump the jar on the ground once every half hour to keep it fluid.

 

 

wow. even with dry ingredients?? So i go give it a few shakes and thumps, it will keep it good?

[dagabu]

Meh? It seems to work for me.

[Peret]

The surface atoms of charcoal exhibit quite a strong van der Waals force - that's a weak atomic force that, for example, gives wax and polythene their physical properties. Fresh out of the still, the charcoal will adsorb nitrogen from the air if there's nothing else, until the force is neutralized. It has its preferences - it doesn't care much for water and alcohols but it likes halogens and hydrocarbons, which is why activated charcoal makes such a good filter. When you mill fresh charcoal it's constantly breaking new surfaces that attract each other, hence the clumping. It's actually a good sign because it means the charcoal isn't contaminated with anything else.

 

Like jwitt says, unless your charcoal is very fresh, roast it before you use it. It's a filthy job but it improves the performance of commercial airfloat at least. I roast mine to drive off any contamination (particularly oils) it's picked up along the way. Perhaps it drives off water also, but since I wet-corn my powder it would seem a bit superfluous to worry about that.

[aftertheaftershock]

The surface atoms of charcoal exhibit quite a strong van der Waals force - that's a weak atomic force that, for example, gives wax and polythene their physical properties. Fresh out of the still, the charcoal will adsorb nitrogen from the air if there's nothing else, until the force is neutralized. It has its preferences - it doesn't care much for water and alcohols but it likes halogens and hydrocarbons, which is why activated charcoal makes such a good filter. When you mill fresh charcoal it's constantly breaking new surfaces that attract each other, hence the clumping. It's actually a good sign because it means the charcoal isn't contaminated with anything else.

 

Like jwitt says, unless your charcoal is very fresh, roast it before you use it. It's a filthy job but it improves the performance of commercial airfloat at least. I roast mine to drive off any contamination (particularly oils) it's picked up along the way. Perhaps it drives off water also, but since I wet-corn my powder it would seem a bit superfluous to worry about that.

 

 

Wow that sounds like a deffinate answer, Is that the only cause of clumping or can there be others. Something like electrostatic charge

 

Bad for us pyros, but has anyone tried spraying their ball mills with the anti-electric charge spray and then milled to see if it clumpes while milling?

 

Oh yeah, hello everyone my first post.

[gera229]

Works for me.