wash it of with water and soap
Flash powder was invented by a man named Joshua Lionel Cowen. He registered for a patent in 1899 for the flash powder to be used in photography.
Early flash powder was made of thermite. And yes, it was extremley messy and if the pan holding the flash powder wasn't held carefully could easily cover everything
No flash powder is stronger and also more unsafe! I suggest reading up on the matter if you would like to know more.
Flash powder.
Fine Alumimum powder and potassium chlorate or perchlorate
Black powder explodes. Flash powder burns extremely fast (that's why it "flashes") and can be dangerous if you don't handle it right.
You cannot buy flash powder online or at any other store - that would be like buying C4 over the Internet. You would need to make it yourself from an oxidizer and aluminum or magnesium powder.
you can't buy flash powder. it is used to make firecrackers and explosives, so it is not commercially available. You can make it from an oxidiser and a metallic fuel such as KClO4 and Aluminium.
Wind.
The autoignition temperature is 590 oC.
Black powder, in fact is the term used in fireworks. Otherwise, it may be referred to as gunpowder although black powder has now become a more acceptable term because it is no longer used in guns(except for the antique ones). Guns now utilize smokeless powders.
Wikipedia has extensive information on the origins of gunpowder / flash powder you should be able to find a wealth of information there.