When changing the flint in my torch sparker I began thinking about the flint. I know that flint is a stone but the sparker flints do not seem like stone. They are too soft. Stone would wear the metal scraper very quickly. It almost seems like some kind of metal. Does anyone here know?
Pete.
Lots of metals, up to 30.
A recipe might be 20% iron, 5% zinc, 5% magnesium and 70% rare earth metals high in cerium (as much as 35% of the total) for a high performance flint with the rare earth component being reduced for cheaper flints
The exact composition is largely determined by the rare earth metals tending to occur together and being expensive to separate. As this application isn't very critical no great effort will be made to ensure pure components. The composition will vary over time with the base ores and the demand/price of specific elements eg if Ytterium or Neodymium happen to have a high price at the time some effort will be made to remove them.
A key point is that with a stone flint/steel striker (eg flintlock) the sparks mostly come from the steel. With a artifical flint/steel striker the sparks come from the artifical flint
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Ferrocerium, a mixture of iron and cerium. Look it up, or look up "pyrophoric," to learn more.
As you probably have realized, the steel in a pyrophoric sparker serves the opposite function of the one in a flint-and-steel set. With flint-and-steel, the steel sparks from the heat of friction, as tiny pieces are scraped off. The steel actually burns.
With a ferrocerium striker, the striker wheel is steel, and the ferrocerium is the material that sparks.
Ed Huntress
Lighter "flints" are not flint. Google "mischmetal", 5300 hits.
Interesting, but have you ever struck two flints together? You get a spark that way too.
Dan
Yeah, I think I tried every combination in the neighborhood when I was a kid. Not many of them worked for me, but we got lots of sparks from rock-on-rock.
My understanding is that steel is good because you get a pretty good-sized hot mass out of the deal, and some of them are actually oxidizing as they strike your charred rag, or gunpowder, or whatever. You need a hard piece of steel (worn out files are good) and a hard piece of rock. Here in NJ, it's difficult to find one hard enough.
The physics, as I've seen it described, derive from the surprisingly high concentration of energy at that steel/rock point of contact.
Ed Huntress
The concentrated energy derives from both the "hardness" of the pieces and the composition. The harder the point of contact, the "narrower" the microscopic contact points, and therefore the area. Pressure equals force divided by area.
All the old iron had pretty high carbon content, which is why you get so many sparks when grinding an old file. But you get no sparks at all from brass, wood, etc. The hot particles are there, they just don't oxidize and incandesce like the iron oxide. I'm sure you know that, just another point to make for the casual readers. Brent Wegher
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