16 replies to this topic

[Techohead]

i've been running my ball mill for the last 35 hours, with 500 grams of black powder inside, and 80 pieces of my milling media. just now i opened up the mill to take out the finished powder, and noticed that there was no powder, just 80 1" marbles. in the centre of each of these marbles was a piece of my milling media. the marbles are rock solid, and i cannot even break them open in a clamp. so as to get my milling media back, i set the marbles on fire in one of the largest fireballs i've ever made. this got my milling media back to opperational standard, however the inside of teh milling drum tooo is covered in rock hard BP. i cannot get it out, but cannot burn it out as that would cause an explosion fatal to me, and i somewhat like being alive. can anyone tell me why every surfact inside my mill is covered in rock hard bp, and are there any suggestions on how to get it out withoug filling it with water, because i hope to save any powder i can, and more importantly, what caused it, so i can avoid it happening again. all i can think of is the really high humidity at the moment may have caused the powder to start clumping, as it may become the slightest bit moist.

[cooperman435]

what was in your mix?

If it contained dextrin and may have gotten damp then that could explain it. You should be able to simply soak it out of your jar though same with the media.

[Techohead]

yeah... it's standard BP 75:15:10 +5% dextrin. and i would never be able to separate the black powder out of the 6 litres of water it would take to fill my milling drum, so i torched the media, and chiseled what i could out of the drum, lit that, then threw a match in the drum, knowing there was next to nothing left. i just refilled the drum with another 500 grams of BP, and teh media and sealed it off with hot glue so no moisture can find it's way into the mixture.

[marble]

Using marbles eh

Marbles are not exactly the best media to use, much to light for BP but they are good for lighter things that need grinding up. Most likely your issue was caused my moisture. Its not the weirdest thing I've seen a ball mill do, I remember seeing a photo of a ammonium perchlorate egg that someone found after attempting to mill some down a bit.

[Arthur Brown]

Simply the transition from ball mill to star rolling drum!

Ball milling ingredients is usually done dry so no problem probably your mix was just wet enough to coalesce into balls / stars using the media as large cores!

BP should be about 70% KNO3 which is soluble in hot water so a flush with very hot water should help.

This would be recoverable by evaporation and re-milling the dried powder. Or you could research the "CIA method" of making BP and just recrystalise the wet mix from a warm alcohol and water mixture

Added- Just seen somewhere else that this is a common problem if the ingredients start out too damp! They may not look damp but sometimes a very gentle warming of the ingredients drives off moisture to enable a good powdery milling.

Edited by Arthur Brown, 25 January 2008 - 09:12 AM.

[phildunford]

Very easy for the charcoal to pick up a lot of moisture, especially if it's stored outside or in a shed before you break it up...

If I'm unsure, I spread it out on a baking tray in the oven and give it and hour at at gas mark 1 to dry it out.

Don't tell the other half though! lol

[pyromaniac303]

Marbles are not exactly the best media to use, much to light for BP but they are good for lighter things that need grinding up.

Worse than that, I read somewhere that small glass fragments can sensitize BP, and even ignite it when dried in bright sunlight.

[BigG]

Worse than that, I read somewhere that small glass fragments can sensitize BP, and even ignite it when dried in bright sunlight.

Guys - he did not say he uses marbles. Read his post again. And please don't start about marble media again. We beat that subject to death on another thread a while ago.

[MDH]

Silicon dioxide does not ignite BP in sunlight. What the heck?

I think you should add the dextrin after you have milled the black powder. Mill the black powder a little bit dampened. When you are done, screen it through a fine mesh.

Edited by MDH, 25 January 2008 - 03:25 PM.

[cooperman435]

I think the process of glas ignitiong bp would be more due to the physical properties of light reflection and intensifying rather than chemical formula.

I wasnt suggesting getting back your BP Technohead just the safest and easiest way of cleaning out a hard caked jar without damaging it.

[icarus]

i dried my charcoal in a hot oven it was quite finely ground i opened the oven door to a nice warm glowing barbecue of lit charcoal on my wifes baking tray so even charcoal needs a bit of respect its quite difficult hiding a baking tray!!!! but its great fun watching the red hot glowing cloud as the lit charcoal blows away outside the joy of an outside oven

[paul]

Why was there a need to DRY your charcoal?!

[icarus]

charcoal for rocket motors is a low performance barbecue variety I rough crush and mix a 10 kg bag so each batch ground has roughly the same characteristics .When purchased from a local garage or diy store it is quite damp. I check by heating 2kg to 120C then re weighing .Once dried i keep it in sealed bags ready for milling as needed . If i dont dry it then it occasionally clumps in the ball mill when fine milled

[Techohead]

Using marbles eh

Marbles are not exactly the best media to use, much to light for BP but they are good for lighter things that need grinding up. Most likely your issue was caused my moisture. Its not the weirdest thing I've seen a ball mill do, I remember seeing a photo of a ammonium perchlorate egg that someone found after attempting to mill some down a bit.

simple mistake you made marble, teh marbles were made of black powder, i'm using marble as a term instead of sphere for teh sake of simplicity. the marbles spheres were about 1" diameter, and made of rock had black powder, with my iron cylindrical milling media in teh centre.

[marble]

I see

Interesting way of making stars