It doesn't work the way you're thinking.

[She amends, shaking her head.]

I don't cause the explosion. I soulcast the materials, and those cause it. Soulcasting is taking a substance, and using stormlight to transform- right now I could take a glass of water, and turn the contents into a rock the size of my fist. Or, getting through a panel earlier, I turned key connecting pieces of the metal itself into blood. Oil and fire are both possible.