Aaah, I remember back in the day when you could walk into Penge nick with your ID, fill out a form and walk out with your black powder licence. Then over to Catford gun shop for a kilo of black powder, no questions asked, and bring it home on the bus. Happy days 😀
I’ll try to find the diagram to make flour violently combust.
Meanwhile if you search Amazon for Potassium Nitrate then scroll down