Melting BP - Well, sort of...

[Ollie Snowie]

I have had a nagging idea for quite some time now, and I have just tried dreaming it up. Here goes:-
I know how thorough incorporation of the chemicals used in BP greately improves its performance, and I know that most people moisten the finely ground sulfur\charcoal mix with water and then mill it with the saltpeter. This method causes the saltpeter to crystalise on the particles of sulfur and charcoal, bringing the chemicals very close to each other.
Well, I just tried mixing the finely powdered charcoal with sulfur and melting the two together in a tin. I ended up with a black mass of solid lumps. Notice how they were black, showing that the sulfur had really been absorbed into the charcoal (well, it could have been heated close to its boiling point, making it turn black, but I didn't notice much sulfur vapour or SO2). I then crushed these lumps again and mixed them with saltpeter and water, to a runny consistency. They are drying right now. The ratios used were 18 parts KNO3, 8 parts sulfur and 5 parts charcoal briquettes, all by weight. I was impatient so I dipped a metal rod in it and heated it to dryness. When lit it made a good sparkler, despite the metal rod to carry the heat away.

A litte off topic but while I was heating the sulfur and charcoal I noticed a funny smell that wasn't SO2 or H2S, so I was wondering if it could be CS2. I have never smelled anything that was definitely CS2, so I'm not quite sure. I have heard that it is quite poisonous...

I am also wondering about BP made with plastic sulfur, although it would probably not stay plastic for long.

[Mumble]

That smell very well could have been Carbon Disulfide. I know it can be prepared by heating the elements together. I tried this once, but failed when the aparatus broke. It was a beverage bottle so it doesn't suprise me. Every time I've been in contact with CS₂ it always smells like Hydrogen Sulfide. Perhaps yours was different because it was freshly prepared.

Just a note of correction. I believe ball milling together makes the Potassium Nitrate crystalise <i>inside</i> the porus charcoal particles. If you really want to make good bp, you really should use willow or grapevine or something like that. Charcoal briquettes, at least the ones I've encountered, make bad bp, but are good for sparks.

[Ollie Snowie]

I've often heard about making your own charcoal, but mainly I can't be bothered and the BP I make can explode quite nicely if confined. True, charcoal briquetes are not the best, that's why I said that I was using them, so you could at least know that the BP would not have been very good if it hadn't been incorporated this way (I select the softest pieces of lumpwood for "bang" BP. This was for a fountain.). It was just so you don't get put off by the (probably pitiful) results and decide not to try this (perhaps useful) new way to make BP.
Perhaps the sulfur getting soaked up into the pores in the charcoal will not help, because it may stop the saltpeter soaking in as well.
I will tell you the results when the BP is dry.

[Third_Rail]

Combining the chemicals like that is certainly an interesting idea, I'd love to hear the results when you get around to it. Mainly, I wonder if it was worth the trouble; perhaps a small increase in power/burn rate, etc.

[Ollie Snowie]

Nope :(. I'm sad to say that I made a few fountains last night and they were not much better than the ones made with normal fountain powder. I got a video of one of them. It needs cropping down though (~4Mb). Even so, I think it is definitely easier to make than normal BP - It doesn't need all that milling. To make this I just ground the S and C until they would pass through a fine sieve, melted them together, ground them until they would go through the sieve again and mixed in the saltpeter and water to make a slurry. No more grinding required. Adding the water and evaporating it makes the saltpeter crystallise on the S and C - just let the water evaporate. As I said, I got results about the same to normal fountain mix with this (the normal fountain mix had been laboriously ground.).
This mix is very slow burning compared with the norm. but makes a fountain of sparks about the same height - less intensity though.

This is a little off topic, but I make fountains a different way from most people - I got very poor results with the normal method, so I tried making them like a firecracker (I tried both M80 style and polumna style.). I find that the M80 style one is more reliable in the way of not going out but the polumna style is better for not falling over (none of then have ever fallen over so I'm guessing this because the M80 is cylindrical and the polumna is sort of pyramid shaped.
With both of these, there is more surface area of burning so they more sparks (less of them stay inside the firework.).
I have to say - the polumna style fountain is very short lived.

[Crazy Swede]

Ollie, I didn't quite follow your procedure.
How much did you grind the final, dry product?

Because if you just used it, without any further grinding, then a large portion of the potassium nitrate will exist as large crystals and therefore make the powder slow burning!

[Ollie Snowie]

I ground the powder until it would pass through a 0.5mm sieve after it had dried and also before I added the saltpeter.
As it was for a fountain, I didn't mind it being slow burning, in fact I quite liked the fact that it lasted longer than the BP made by ball milling. I'll put the video on the FTP when I have cropped all the night sky out of it. (Chemwarrior - the video is not very high quality but it will be very small when it has been cropped. I suppose you don't mind videos being bad quality as long as they are not huge and wasting bandwidth. Please email me if otherwise. You have my email address.)
Also, I'd have thought that grinding it a lot after it had dried would just knock the crystals of saltpeter off the charcoal and sulfur, making a slow burning probuct that behaves as it it hasn't been incorporated. I notice that when I do grind the dry powder up a lot then it turns sort of grey, so I think that this is showing that the saltpeter has been separated from the charcoal (You know how quartz crystals are clear when intact, but when smashed, the smashed surface goes white and opaque.).
I will try grinding it to a fine powder and comparing it to the coarsly corned BP.
I forgot to mension that I didn't just leave the wet BP sitting around to dry; I put in in a saucepan with pennies to break it up, and swirled the saucepan around for a while. I ended up with litte round balls that would probably make great stars, but I didn't want stars, so I pushed it through the 0.5mm sieve again (while moist).

[Crazy Swede]

Ollie, intimacy between particles will never decrease because of milling or grinding! :rolleyes:

If you would like to optimize the burning speed, all ingredients must be as fine as possible, prefferably as meal. A particle size of 0.5 mm is way too coarse!