Master Crafting: Using an Orb of Scouring on a "Prefixes cannot be changed" item does what?

If you have the "Prefixes cannot be changed" suffix on an item and use a) an orb of scouring or b) a chaos orb, this is what happens:

a) The scouring removes all suffixes, leaving you with an item that only possesses prefixes.
Note: This also removes the master craft "prefixes cannot be changed".
After scouring you might then just slam exalted orbs on it and hope, or meta craft "can have multiple crafted mods" or some shit.

b) The chaos rerolls all suffixes leaving the prefixes alone.
Note: This also rerolls the master craft "prefixes cannot be changed". So in order to "easily" reroll an item until it is perfect you would have to spend 2ex for the mod, then 1c to reroll, 2ex again on the mod... etc. This is risky since it might roll you 3 really bad suffixes ruining your item for all eternity.

Prove: https://www.pathofexile.com/forum/view-thread/1401804

SumoFlorist is correct.

One addition. IF you want to craft good suffixes on an item you would not go with the chaos orb way, but rather the exalt way:

1. prefixes can not be changed
2. scour
3. exalt - if bad roll > return to 1, if good roll > proceed to 4
4. exalt - if bad roll > return to 1, if good roll > proceed to 5
5. master craft last suffix