Rear Brake Master Cylinder parts

Well,today I could bleed the system to 90%,now its a bit spongy but I recovered the brake.
What I did to get pressure was
1)I took the caliper out from the rotor
2) I put beed neeple hose upper than the caliper upper than the hose than the master cylynder

basically I hanged all the system and used the gravity to bleed the air
I think my cavity theory was right and there was a "air cell" near the pistons,which I bleed following the method described above.

Hopefully tomorrow I´ll test the brake and see what happens