Odds of upgrading from uncommon to rare in MF
I don’t believe that is possible. I think the most you can do is upgrade one tier. So you would have to throw in 4 masterwork items. They say it’s 20% chance for an upgrade, so I must have been extremely unlucky my past 10 tries (all masterwork)
RIP in peace Robert
Like Ethics has stated, you can only jump 1 tier at a time.
So your uncommons (blue) will go up to masterworks (green) first, depending on your luck it may or may not upgrade. However long haul testing has shown that the rate to upgrade evened out at ~20%.