Phinneas Nigellus Black agreed to help Snape test his potion so long as his questions remained respectable and Hermione returned his portrait to Grimmauld Place. Bee assured her Kreacher would allow her to deliver the portrait. Phinneas swore to remain out of sight to keep from alerting anyone of his freedom from Hermione's bag. After some trial and error, Snape created a formula that had the potency of three drops of veritaserum and lasted for six hours, far longer than Hermione hoped to need. "I will leave my personal floo open at 9 am Saturday. Please remain in my private chambers until I come to collect you. Once I am assured the nosy gits are occupied we can begin.