Meal powder is the fine dust left over when black powder is corned and screened to separate it into different grain sizes. It is used extensively in various pyrotechnic procedures, usually to prime other compositions. It can also be used in many fireworks to add power and substantially increasing the height of the firework. Meal powder is a side product of milling high-quality black powder. It is also a mixture of potassium nitrate, charcoal and sulfur in the correct proportions (75:15:10) which has been ball milled to mix it intimately. It is used in the same way as commercial meal powder or can be pressed and corned to produce true black powder.
These ingredients are processed in a ball mill, basically a spinning drum with non-sparking ceramic or lead balls. The more time left in the mill, the more "explosive" the powder will be. One main reason to ball mill as opposed to other methods is because it presses sulfur and potassium nitrate into the porous charcoal.
Grind each chemical separately as fine as possible. A ball mill or mortar and pestle is good, but the job can be done much faster using a coffee grinder (the finer the powder is, the faster it will burn). Grinding an oxidizer (Potassium Nitrate) together with fuel (Charcoal) with metal blades is a bad idea as it may combust. If you grind chemicals in coffee grinder be sure to have one for fuels and one for oxidizers. Screen the chemicals together and pass several times through mesh screen. Place the green mix into a ball mill with non-sparking milling media. It should be milled for at least 3-4 hours.
It has many uses including prime, dusting, a general ingredient in some compositions and preventing stars from sticking together during manufacture.