Blaze powder and rod is used in few recipes.

[iTitus]

• 2 brewing recipes (but they have alternatives)
• H.S. Rail in the Rolling Machine (shaped) (and all child recipes)
• Blazing Electron Tubes in the Thermionic Fabricator
• Blaze Stick in the Assembly Table (=> Portable Laser in the Assembly Table)

[asiekierka]

You can now make blaze powder out of gunpowder, and blaze rods out of blaze powder.