I was wondering what are sparks, or of what are they made of? I read in this wiki article that they are simply some incandescent particle, so, does that mean that any small mass of material, heated to a temperature that makes it shine emitting visible light counts as a "spark"? Of course, spark is not a precise mathematically definable concept, I'm mostly wondering what are sparks made of in the following circumstances:
Sparks are tiny pieces of material that are hot enough to produce visible light. With fire, it is tiny particles of burning wood. In welding, it is the superheated welding material. When smithing, it is tiny chunks of the hot metal. For flint and steel or any other hard object scraping cold metal, it's the tiny flecks of metal rapidly oxidizing and heating up.