Always add new plaster next to a section with a wet edge to avoid creating the dreaded “cold seam”—a hardened ridge that can show through the top layer. So if you’re breaking up the project over many hours or days, be sure to finish a complete wall in each session. Allow the bottom coat to dry completely (drying time will generally be between 4 and 8 hours) before repeating these steps for the second coat. This time around, you have the opportunity to show off how far you’ve come with your technique by layering the top coat on just 1/32 inch thick.
Buff the Surface
For a soft, matte surface, burnish your wall with a damp tile sponge, rubbing lightly in a circular motion. For a hard, polished surface, opt for a trowel finish, applying pressure on the trailing edge of the trowel as you sweep it across the wall.
The most basic way to burnish plaster is with a sanded finish, which requires only a thin coat of water and a tile sponge. Burnish when the top coat of plaster is still damp, but dry enough so that slight pressure with your thumb doesn’t mar it. Use a sprayer to lightly mist the wall, and rub the wet area in a circular motion with an almost-dry tile sponge, using light pressure to compress all the layers. Remove the painter’s tape when the plaster is still damp. After the wall has dried completely, wring out your tile sponge and wipe the wall in broad, overlapping arcs to remove excess sand.
There are infinite combinations of clay plaster recipes, pigments, and techniques to discover. So don’t be afraid to investigate and experiment. Regardless of how you choose to play with your mud, clay plaster gives your home a warm and sophisticated wall finish that will satisfy both the child and the adult in you.