about the probability of an item rebirth

[AmbroseRookwood]

i upgraded a Iron Bow +1 rev wioth out tears and i made it to +3 then stopped and sold it.. no burns or anything.. and ive never upgraded a reb item before..
the next day i tried a 2 do it with 2 mirage daggers and a shard rev+1 they all broke going to Rev+2 and the iron bow made it straight to rev+3 no prob..

Upgraded a chd from +1reb to 5reb in 3days, using tears broke no other reb items in between ...

[Homestory]

Just made a +4rb shard from +1 using tears, its like anything only risk what u can afford xD