Hello
What material do you use to separate acrylic from a printed formlab model?
Would you mind going into a little more detail about what you’re trying to do? 
Orthodontic applications 
The lab I use for acrylic Hawley retainers apparently uses mineral oil as a separating medium on the printed dental models I send them (using Gray resin). The lab tech says the retainers are difficult to remove from the resin model because of the small mechanical undercuts that don’t break loose like on a stone model.
Cheapest is butter but best is Dentaurum 3D Separating medium.