Another early method for testing liquor's alcohol content was the "gunpowder method." Gunpowder was soaked in a spirit, if the gunpowder could still burn the spirit was rated above proof. This test relies on the fact that potassium nitrate (a chemical in gunpowder) is significantly more soluble in water than in alcohol. While less influenced by temperature than the simpler burn-or-no-burn test, gunpowder tests also lacked true reproducibility. Factors like the grain size of gunpowder and the time it sat in the spirit impact the dissolution of potassium nitrate and therefore what would be defined as 100 proof. However, the gunpowder method is significantly less variable than the burn-or-no-burn method and 100 proof defined by it is traditionally defined as 57.15% ABV.