What is actually getting multiplied when Compounding?

[Nalthian Customs Official]

I looked around to see if anyone has raised the question before, and on the Compounding page on the Coppermind.  As far as I can tell, Feruchemical attributes are stored as two components: the percentage of the user's attribute that has been stored, and the length of time that it was stored for.  Compounding multiplies the Feruchemical attribute using Preservation's power by having the metal act as a new sort of key for the power, and it is generally assumed that the amount of power released is proportional to the amount of power that was already stored in the metalmind.  The figure that has been thrown around in and out of the books is ten times, though I am sure that number varies with the strength of the allomancy the compounder has access to.  

My question is, what is being multiplied by ten when burning a metalmind?  Is it the percentage, or the duration?  Using the typical Feruchemical example of 50% of one's strength at 1 hour, if someone compounds that, do they receive:

500% of their strength for one hour

or

50% of their strength for ten hours

or

some combination, like 250% of strength for five hours.  I personally think this gets a little too complex and is not likely to be the answer, though I could be wrong.  

In any of these cases the user modifies it from there based on their needs, just like all Feruchemy.  However, 50% of strength for ten hours does not equal 500% of strength for one hour, due to compression of investiture.  If the percentage was being multiplied, losses to compression would not be as big of an issue, and the only limit would be the amount of metal one had access to and could burn, rather than the availability of metals and loss of investiture to compression.  I personally think that the duration multiplies rather than the percentage. 

What do you all think?  Am I overthinking this?  

[Treamayne]

17 hours ago, Nalthian Customs Official said:

My question is, what is being multiplied by ten when burning a metalmind?  Is it the percentage, or the duration?  Using the typical Feruchemical example of 50% of one's strength at 1 hour, if someone compounds that, do they receive:

500% of their strength for one hour

or

50% of their strength for ten hours

or

some combination, like 250% of strength for five hours.  I personally think this gets a little too complex and is not likely to be the answer, though I could be wrong.

Based on what we know so far, you may simply be overthinking this. If Ferchemical Storage is an equation:

• T*P=I
  • Time (T) * Percentage of Attribute (P) = Units of Stored Investiture (I)
• Then Ic = 10I
  • Compounded Investiture (Ic) = 10 times the value of I
• Therefore, it can be Tapped/Used with any Time or Percentage Variable (it does not have to match the rate of storage nor the time of storage)
  • Ic/P = T
  • Ic/T = P

So, if you are Tapping for a high percentage, the time using the Compounded Attribute is reduced (much like Feruchemical Compression of an attribute - you just have more Investiture from which to tap). You can also store the output of the Compounding into new metal minds and use it slowly, over a longer timeframe yeilding longer access to a lower Compounded percentage. 

Note: This is why Ruin was able to change the contents of a Coppermind - because Ati was making changes during the conversion process to or from storage (or both). WoB:

Spoiler

Questioner

In the Well of Ascension, Kwaan says that Ruin changed the words in the Feruchemists' metalminds. Ruin can't *inaudible* metal plates. I was wondering what the difference was?

Brandon Sanderson

Because they're in the person's head before they're going in the plates. And he can affect the power as it's transcribed between. Because the power is partially him, the Power of Creation of that world. So there is a bit of him inside of every person, and as the power is going from person into plate... It's kind of like how people can hack your phone through your wifi. Does that make sense? So, that's what's going on there.

Arcanum Unbounded release party (Nov. 22, 2016)

Hope that helps

Edited October 20, 2025 by Treamayne
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