Titanium!

Sample: Titanium wire.
Source: Old-school flashbulb.

In the day before compact high-voltage charging circuits and xenon flashtubes, the illumination for cameras came from a small one-use class ampuole filled with titanium wire and oxygen. A small battery was linked to the shutter and a small black powder pellet inside the flashbulb. Triggering the release triggers the charge, which makes the titanium oxidize. Titanium is an extremely reactive metal, and oxidation releases a bundle of energy in the form of light and heat. They commonly caused fires and severe burns.



Titanium, 10x.



Titanium, 60x.



Titanium, 200x.