Plaster encompasses a wide variety of terms and different products. Some plasters like plaster of paris, calcium sulfate hemihydrate, and cement are chemically reactive plasters that rely on water as a catalyst. Other plasters like gypsum, gypsum with polyvinyl acetate, and hydrated lime rely on evaporation. There is a common misconception that joint compound (drywall mud) is not plaster. In fact, they are it just depends on product application.
Customers have a variety of options once the gypsum panels are installed. They can choose to have drywall mud applied to screw heads, paper tape seams, and drywall corners and or trims. Resulting in a semi-smooth state often referred to as white boxing or white boxed. From there they may wish to perfect the semi-smooth to a level five grade of smooth. Or they may decide to texture the drywall hiding imperfection. There are many selections of textures to choose from so of which include heavy to light splatters, orange peel, heavy to light knockdown texture, Spanish lace, and faux sand finish. These are typically used as wall textures. Common ceiling finishes include stomp, crows foot, popcorn, acoustic, and faux sand finish.
On the other hand, some customers may choose plaster. Plaster is applied to the entire surface of the gypsum panels, seams, and plaster mesh corner beads or trim. Typically a basecoat plaster followed by a hydrated lime and sand mixture is applied to create the traditional sand finish, skip trowel, or mitten texture. If the customer prefers a smooth texture. A calcium plaster would be applied and polished with a trowel, or textured without the introduction of any sand.