OK i know there is KNO3 in stump remover but how do you extract it so it's really pure, or is stump remover all KNO3?

IT's 95% pure and will work for most pyro applications. If you're doing something that requires really really pure KNO3, though, you can dissolve it in water and filter out the non-dissolvable impurities.

more on that here: http://krimzonpyro.com/ep/projectsdevicesdir/kno3.html

WOW 95% pure thanks.

Some brands use different amounts. Just mix 1/4 teaspoon of powdered stump remover and 1/4 teaspoon of sugar. Hold a lit punk on the pile, and if it doesnt light you should consider buying another brand, or at least purifing it. It it burns then you got the right stuff.