1) Why the South door is actually the most importantThe South door (with its doors by Andrea Pisano made in 1330) is actually the Baptistry’s main door and it should be considered the most important because it’s the oldest. Furthermore, as it’s south-facing, it was the door through which Florentine godfathers used to enter holding the precious newborn. Lorenzo Ghiberti, when he was commissioned almost a decade later to do a second set of doors for this building, paid homage to Pisano’s doors by creating its important frame (it was designed by him and executed by studio assistants who went on to become the most important sculptors of the second half of the Quattrocento: Pollaiolo, Rossellino, and Verrocchio).
2) Pisano’s doors were never the east doorsIn his Lives of the Artists, the art historian Giorgio Vasari claims that the South doors by Pisano were originally placed across from the Cathedral (i.e. the East doors where Ghiberti’s Gates of Paradise now stand). This cannot be true: Pisano’s doors are just slightly taller than the East doors by Ghiberti and they wouldn’t fit in the door frame! Vasari probably writes this white lie to add importance to the Gates of Paradise, in part for political reasons: the frame of the South door alludes to the Florentine Republic, which Vasari prefers to avoid since he is writing while on the Medici’s payroll.
3) Ghiberti won because he cost lessThe commission for the North doors was awarded to Ghiberti through a public “contest” in which the runner-up was Brunelleschi. Both were asked to depict the scene of the Sacrifice of Isaac (the originals are now on display in the Bargello Museum). Ghiberti’s relief weighed less, and thus cost less. Aldo Galli suggests that this economic factor played a part in Ghiberti’s win.
4) Magical animals and insects warded off evilOn Ghiberti’s first set of doors, between the quattrofoils there are plant and animal decorations. Of these we note insects and animals known for their harmful characteristics. The life-size carpenter ants, beetles and locusts were in some cases cast from the real things using a technique described by Cennino Cennini. By medieval logic, representing these evil things was a manner of keeping them away – the doors thus gained amuletic quality. [article] On the frames of the east and north doors there are garlands of flowers and fruits inhabited by reptiles and mammals. The amuletic quality of the insects applies here too to ward off animals that could harm harvests.
5) The frame of the north door was done in a hurryAs you know, Ghiberti was commissioned for a second set of doors (the Gates of Paradise) after completing the earlier ones (the quatrefoil ones with the scenes from the life of the Evangelist) that were initially intended for the East door. Ghiberti had made the frame for the east door. The newer doors were installed there and he had to hurriedly create a frame for the north opening that welcomed his earlier creation. If you look closely you can see this hurry reflected in the errors of fusion that the bronzeworkers made.
6) Adam and Eve were against drugs
On the South door frame, figures of Adam and Eve are an allegory of Salvation and a discreet anti-drug campaign. Eve is pictured with attributes associated with witchcraft (spindle and distaff) and misfortune (instability shown through a wind-driven sail) and she is decorated with garlands of hallucinogenic plants used to create a “witches’ oil”. While witches said they flew on brooms, it can be said that they were actually under the effects of drugs. The image of Eve is balanced out by that of Adam who, accompanied with Saint John the Baptist, are characterized by good plants like olive, lilies, and grains. [article]