Epson WorkForce Pro WF-R8590 DTWF - Manual (Page 127)

Note:
If there is protective material attached to the bottom of the ink supply unit, remove it. The shape and number of
protective materials and where they are attached are subject to change without notice.
5. Shake theink supply unit 20 times well.
6. Insert the ink supply unit into the ink case so that it fits into the printer.
User's Guide
Replacing Ink Supply Units and Other Consumables
127