Ah, Blackpowder. No web - community website with respect for itself would be complete without some recipe or another. So Everything2 might as well have a good'un.
The quick version:
75 % KNO3
15 % Carbon
10 % Sulphur
Mix and set on fire. Boom.
The long (and, quite frankly, more useful) version:
To make decent blackpowder, you need a ball-mill: A mill which uses heavy steel balls to crush chemicals. A little bit advanced for beginners, so let's go for a slightly simpler solution instead:
This method is based on the fact that KNO3 is highly soluble in boiling water, and the fact that the same chemical becomes a lot less soluble when you add alcohol to the mix - apart from this, you'll need an absolute minimum of equipment. So: Let's go!
Stuff you need:
To make about 200 grammes of black powder:
Measure 30 grammes of Carbon and 20 grammes of Sulphur. These need to be completely powdered - use a pestle and mortar or something like that. Mix it through piece of fine-masked textile (a nylon stocking, for example) and the pieces that don't go through will need to be crushed further. You want no lumps in your mixture.
Now, measure 150 grammes of Potassium Nitrate in 70 ml of distilled water (regular tap water can be used, but distilled is better). When it starts to boil, add the C and S.
Mix until everything is a thick, dark sauce. Congratulations, you now have blackpowder - so be careful.
Take the mixture off the hob, and leave it to cool a minute or so. It may be useful to take your mixture outdoor, as it is now extremely flammable, although it won't explode if it does catch fire, but chances are you can kiss your eyebrows farewell - if you're lucky.
Carefully start heating your mixture again, and add 60 ml alcohol, and stir vigorously. The alcohol will boil, and the fumes coming off your mixture will be highly flammable. This is a strictly non-smoking operation, in other words.
When most of your alcohol is boiled away, add another 20-30 ml, and repeat the above procedure.
Leave it to cool. Move all your mixture onto a strong piece of fabric. Collect all the corners, turning the fabric into a ball - Wring this, so most of the liquid in your mixture falls out.
Take your dry-ish ball of blackpowder, and granulate it into tiny chunks. Use a regular kitchen grater or something. Spread this on a piece of paper, and leave it to dry completely. Don't use heat to dry this, for obvious reasons. Patience is the only way.
When it is completely dry, you have approximately 200 grammes of premium quality black powder. Use it with care.
Do not try to cheat - there are no shortcuts that can be made in the above recipe. If you try, you might die.
Do use the right materials. Replacing them is possible (it is possible to use icing sugar instead of carbon, for example, but it won't work as well), but not recommended unless you know what you are doing. And if you do know what you are doing, what are you reading all this for?
Don't be stupid. Making black powder is probably illegal where you live, and blowing stuff up definitely is.
So what can this be used for?
Anything, really. You can launch rockets, you can make pipe bombs, you can make M-80s or similar firecrackers. Or you can just light it on fire and be amazed at how fast it burns. Just be careful.
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