Steps to Application
Since lime plaster takes time to sit before it is applied, you want to start this step first. Follow the directions on the plaster to mix in an aggregate in order to properly prepare it for application. It should be a thick consistency (like cream cheese) when it is ready for application.
It is important to start with a clean surface for application. Make sure the wall is free of any old lime plaster and dust. If you are working with wood laths, make sure they are in good condition and not bumpy or damaged. Metal laths tend to last longer, but can be hard to plaster because they are slippery. Spray down the wall with water until it is damp, but not dripping.
It can be tricky to apply plaster if you are not experienced. Take time to apply it carefully between laths and create a flush surface with the wall. The initial coat is called the scratch coat. Once it is applied, let it dry until it is resistant to pressure but still able to be scratched. Scratch the surface using a lathe scratcher and moisten the layer before applying another coat. Then apply additional coats, each with less aggregate, until the wall takes on the look you want.
Lime plaster takes significant time to harden, or cure. If possible, give it several weeks to harden before using the room.