There are 2 vendors out of 3 that carry potassium nitrate. Mine is greenhouse grade. One of my vendors sold me a bag of prilled potassium nitrate a long time ago. Don't know why it would be such a big deal. The greenhouse grade is a fine powder that blends well with sugar, sulfur, charcoal, German black aluminum, etc. I would prefer the prills myself because the powder blows around in the slightest breeze. Dissolving it is not a big deal. I designed my sprayer to have very good agitation.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738