I think just when the toa got the kanohi nuva on their face i think since the toa controled the kanohi i think they automaticly turned into kanohi nuva besides since the toa already had kanohi they must have communicated with the masks of power inside of them and turned into kanohi nuva since the protodermis is the stuff of life it might have transformed the kanohi.

it was a suggested way of thought by gregf that the nuva masks were already on the island,  if you think about it.  the toa were given directions from the turaga of where they would find the masks, they didnt just wander and trip over the things.  so the kanohi nuva could have easily existed on the island, just hadn't been found since the toa led a directed search instead of just combing the entire island.  

btw i think this may belong in theories since it is mostly speculation.

by way of transforming kanohi into kanohi nuva i think ive read it somewhere that the kanohi nuva are actually the kanohi with protodermis around it. i think? im not sure have to check on it.

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Moving to Theories...

I know gregf is right it is just that well if the toa were searching for the kanohi then if the toa haven't found the kanohi nuva then how come if they found them they might have already turned into the... wait a minute if there were only 74 masks( including vahi and mask of light) then did other kanohi get dipped into protodermis too and besides if the toa found kanohi nuva they wouldn't work on the toa because 1:they haven't been toa nuva yet 2: they wouldn't have the power of it since they haven't had the power to control it 3: they didn't have protodermis life in them... well maybe they did but not with the kanohi nuva power! there is a lot of questions to this besides the kanohi nuva were on the island and when the toa turned into kanohi nuva do you think the toa lost the power of the orginal kanohi they haven't lost the power but do you think the shape of the orginal kanohi are no more? besides we will know in time.

Umm... quite.

The accepted theory is that the Protodermis morphed the Toa into Toa Nuva, created Protodermic Armour and Weapons Tools for them, and transformed their Kanohi into the Kanohi Nuva.

We're not sure if, because they had Golden Kanohi, the combined power made the Kanohi Nuva super-strong, of if it was the Protodermis.
Nor do we know how the other Kanohi Nuva are created.

Either way...
That's what I say.