The two metals in fused “fabrials”

[Ceradis]

So at first I was thinking these would be aluminum/duralumin for the ones that block shardblades and conduct Light. However, while the Rosharans seemed somewhat ignorant of aluminum up until OB, in the early chapters of RoW Navani talks about using aluminum in the fabrials of her flying ship so they’re clearly aware of it by now. This makes me think that they would have recognized aluminum weapons if that’s what the fused were using. Any thoughts on what they might be?

Edit: for clarity, I’m referring to the metals in the epigraphs of ch 17 and 18

Edited November 6, 2020 by Ceradis

[Gilphon]

Brandon made a comment on Reddit on wednesday that somewhat addresses this: 

Quote

Oversleep42

I got a question about this and last week's epigraph.

The metals Fused use. How come nobody knows, guesses or even suspects that aluminium and its alloys are Investiture resistant? They know you can Soulcast something into aluminium, so they should also know it's impossible to Soulcast aluminium into something else.

And once they know about metal that cannot be Soulcast, they start experimenting with fabrials - they used that in construction of Fourth Bridge - and then the logical step is to test it against Shardblades.Probably experimenting with alloys of aluminium, too.

Yet the metal Fused use to make weapons resistant to Shardweapons is a mystery to them?

I feel like I'm missing something here.

Brandon Sanderson

They're getting to answers here. Problem is, metallurgy just isn't a big science on Roshar. I feel it's one of those things that is more easy to see externally than internally--and do remember that there are things like god metals (Shardblades, for example) that also behave strangely around investiture. They have far more experience with those than aluminum, which is more of a little historical oddity to them than a big revolutionary part of science. Add to that the fact that some of the metals the fused are using aren't aluminum, and...well, I don't think it's as obvious a leap as you're making it out to be.

ImBuGs

So the Fused's fabrials are not 100% aluminum based? Or they are and they are struggling to reach that conclusion?

Brandon Sanderson

I think what you're asking will be answered in the book, so I'll RAFO for now.

I think what's going on here is that they figured out that the Fused were using Aluminium at some point between the start of the book and when the lecture was given. 

[ftl]

Yeah, the comment that "Some of the metals the fused are using aren't aluminum" definitely implies that some of them *are*. So probably the shardblade-resistant metal is aluminum, and the investiture-draining one might be duralumin, or chromium, or something.

[Leuthie]

It definitely couldn't be Odium providing a god metal that sucks in Investiture. That would be crazy!