Fabrials using Invested metal?

[I think I am here.]

So, I've got a question, or an idea. Or both.

So, you know fabrials, right? The SA contraptions that trap spren inside gems to do things? Well, you may or may not know that they also require metal to function properly. Every fabrial we've seen onscreen has not been without a metal casing, and so it can be assumed fabrials require metal, along with the following evidence:

1. Shallan only realizes the Oathgate is a fabrial from the metal:

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Ten lamps. With gems in them. Latticework of metal enclosing each one.

Shallan blinked, a shock running through her.

"It's a fabrial."

2. Also, this quote from Navani's notebook:

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"For example, flamespren give off heat—and by pressing metal against a ruby with a flamespren trapped inside, you can increase or decrease that heat.”, and again Navani's notebook.

So, we've cemented you need metal for fabrials to work. So that brings up a question for me: What happens if you use Invested metal?

Now, I like fabrials, but I'm far from being an expert, so I'm turning to you guys. I doubt a piece of iron feruchemically charged would have the same effect as a normal piece of iron, as we can see that the feruchemy actually changes the structure of the metal, allowing for its allomantic use to be different. The fact that an Invested and non-Invested metal makes a difference in Allomancy makes me believe it would create another difference in Fabrials. Maybe, since metalminds for Allomancy causes the feruchemical effect, perhaps using a metalmind for a fabrial would produce similar feruchemical effect.

Again, this question also regards metals which have been charged with hemalurgy, as they would be Invested, and it makes me think what a fabrial with a hemalurgically charged base would be like.

Also, although it would be inconvenient, it's also worth thinking of awakened metals. Used as a base for a fabrial, would the metal produce a different effect? Would the awakening of the metal affect the spren inside? All questions to ponder.

So what you guys think? Is there any way some obscure form of fabrial theory can solve this conundrum?

[Wandering Investor]

It depends on the purpose of the metal in the fabrial. If the metal only serves as structural support, that is just holding the gemstones, then probably not any problems. If the investiture of the gems at any time runs through the metal, then there is a problem. Investiture resist other forms of investiture, so the invested metal will resist the stormlight trying to go through it. There's the third option that if the contact of the metal with the gem is what causes the fabrial to start working, in which case I don't think invested metal will cause a problem, but maybe. In any of the scenarios, the magic of the fabrials and invested metals will likely not combine. Using invested metal will either cause no change, or stop the fabrial from working.

[Szmit]

Considering that Shallan's soulcaster needed only modyfication of metal parts to work I think it is verry signifikant. I dont think modified soulcaster would work but simpler fabrials just might.

I think the best bet would be feruchemy since it is the only thing that gets multiplied during burning. (Awakened and hemalurgis metals i think were confirmed to return power weirdly). Probably paired fabrials with strength implanted would consume more stormlight but not break so easily and with speed move a longer range? Warning fabrials with senses could see further?

[Journey Before Pancakes]

2 hours ago, Szmit said:

Considering that Shallan's soulcaster needed only modyfication of metal parts to work

We never saw Shallans soul caster work and I don't think we learned what it would take to fix it.

[Szmit]

1 hour ago, Journey Before Pancakes said:

We never saw Shallans soul caster work and I don't think we learned what it would take to fix it.

Jasnah said that it was easy fix with damaged chain that happens often (if I remember corrrectly)

[Calderis]

1 hour ago, Szmit said:

Jasnah said that it was easy fix with damaged chain that happens often (if I remember corrrectly)

It was Navani speaking over the Spanreed. 

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This happens more often than you’d think, Navani had replied. The failing likely has to do with the alignment of the gem housings. Bring me the device, and we shall see.
“My mother,” Jasnah said, “is a renowned artifabrian. I suspect she can make yours function again. We can send it to your brothers, who can return it to its owners.”

What she says implies that they routinely fix them, they just don't know how to create them.