Step 5: final mix
once you have both materials in the bag, gently rock the bag back and forth about ten times, until the two powders are thoroughly mixed.
Congratulations! You have made flash powder. Be careful with it.
Store in a clean, dry place, in a sealed container, away from children and pets. Store away from sources of ignition, and from other chemicals.
To incorporate your flash powder into flat pack explosives, see my other instructable: flat-pack explosive (squib).