In a pinch, you can weigh out the ingredients for a composition using a balance scale. In a real pinch, you can even make the scale yourself, here's a tutorial: http://www.alysion.o...ocks/scale.html
Say you want to make BP, you need to have 75% KNO3, 15% charcoal and 10% sulfur.
Start by putting half the sulfur you want to use in one weighing tray, then add sulfur to the other tray until the scale balances. You now have the sulfur you need, and one tray holds the weight of 5% of the finished composition.
Keep the sulfur in one tray, and weigh charcoal against it until it balances. Do this three times to get your 3 * 5 = 15% of charcoal.
Now remove the sulfur, put all the weighed out charcoal in one tray, and weigh KNO3 agains this five times, there you have your 5 * 15 = 75% KNO3.
Mix together everything you've weighed out, and voilà, you've made proper green mix with a very simple scale
This method can be used for other compositions as well. It's not suitable for weighing out small amounts of ingredients, since the accuracy isn't that great. If you need you can also get an idea of the actual weight of the material, by balancing it against a measured amount of water (which weighs 1g/cc).
