Meal powder
Meal powder is the fine dust left over when black powder (gunpowder) 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.
'Mill meal' powder is 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.
To make meal powder or black powder, a chemist mixes the ingredients by mass, never by volume. 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 KNO3 into the porous charcoal.