LATE ECLIPSES open thread. Have a party.

I'm interested. :D

I can't answer definitively for why it hurts them *specific* to Seanan's books, but here's what Fishy says about iron in general (edited from IM)...

[13:07] Fishy: Wrought iron is a weird composite of higher and lower levels of carbon.
[13:07] Fishy: Cast iron is very high carbon, 2-3%, which is why it is so brittle.

[13:09] vixyish: I'm just wondering if the wrought or cast iron is pretty far in composition from modern usage.
[13:10] Fishy: Wrought is. It basically does not exist anymore, except in scrap form.
[13:10] Fishy: Hasn't been commercially made since the late 60s
[13:10] Fishy: and even that was a tiny little holdout
[13:10] Fishy: Cast iron is still a modern material
[13:11] vixyish: but is brittle, right?
[13:11] Fishy: Yup
[13:11] Fishy: hence only really used for old school frying pans, that kind of thing.
[13:11] Fishy: Decorative castings.
[13:12] Fishy: Your best bet, metallurgically speaking, to explain why old iron was special was to focus on the composite nature of wrought iron.

[13:13] Fishy: So, you get it from an iron bloom, a smelting process where nothing really quite melts, as that takes some very advanced furnace designs for iron. Instead it just kind of aglomerates into a big spongy mass in the bottom of the furnace.
[13:13] Fishy: With lots of unsmelted slag and unburnt carbon mixed in
[13:13] Fishy: You pull that out and hit it with big hammers while still glowing
[13:13] Fishy: This forced out a lot of the crap and compresses the mass into wrought iron.
[13:13] Fishy: You get a very distinct banding from all the different layers
[13:14] Fishy: It has a grain, basically.
[13:14] Fishy: In modern terms, it is a composite, just like fiberglass or wood.
[13:15] Fishy: You've even seen this layering effect, in like old rusty anchors: http://farm3.static.flickr.com/2644/3854292982_9f82bfe9b1.jpg
[13:15] Fishy: Looks like wood grain!
[13:15] Fishy: Different layers corrode at different rates, resulting in that effect
[13:16] Fishy: Makes the iron stronger in some directions than others. again, just like wood.
[13:16] Fishy: You ask me, faeries and vamps share a common aversion to composite materials.

[13:17] Fishy: Here's a better pic: http://www.faqs.org/photo-dict/photofiles/list/3200/4257rusty_anchor.jpg
[13:17] vixyish: so modern iron is not a composite like that?
[13:18] vixyish: I'm not sure the composite explanation would work or the fae, since they are basically medieval tech level and thus use wood for all sorts of things.
[13:18] Fishy: Nope. That only happened because we couldn't get furnaces hot enough, or when we did because we couldn't control the carbon content, resulting in brittle cast iron.
[13:18] vixyish: and they don't seem to mind furniture in the modern world
[13:18] Fishy: Now we can make homogenous steel of any alloy percentages you care to name in vast, vast quantities.
[13:19] Fishy: Well, it could be something specific to iron composites. High carbon hurts in one way, lower in another, but the combination of the two next to each other is the real problem.
[13:19] Fishy: *handwaves*
[13:19] vixyish: *nodnod*
[13:19] Fishy: Prevents blood clotting, maybe.
[13:19] Fishy: Or acts as a nerve agent.
[13:20] Fishy: Sure, sets up a feedback loop between two different pain receptors.
[13:21] Fishy: Choose any delicate biochemical system that is plot-convenient, really :)

So, there y'go. Some *possible* explanations of why, based on the composite nature of iron.

Would also be consistent with why being in a car with modern alloys in the engine is okay (it's only low-carbon iron) but being in a room banded with *wrought* iron (both high and low carbon) is something they can feel in the air.

And why you still wouldn't want to be a fae mechanic, because maybe *touching* the stuff is worse than just having it near you.

*nod* Makes sense.

Though I'm curious about Danny's Gremlin mechanic.

Thanks!

Well, the mechanic part of that was speculation on my part. It could be that only composite iron (the oldest kind) hurts them at all. A mechanic wouldn't be touching that; they'd be touching modern, low-carbon "iron".

This is all fascinating!