How to: Painting Plaster
Plaster surfaces are very good substrates to paint because plaster has good “tooth” for the paint to adhere to, is smooth and reasonably dimensionally stable. However, new plaster will not hold paint well. New plaster contains a lot of water that must come out before paint is applied. If the water is not allowed to come out, the water may force itself through the paint causing blistering and loss of adhesion. Also, new plaster is very alkaline. This strong alkalinity can adversely affect adhesion.
It is strongly recommended that new plaster be allowed to dry thoroughly, at least 30 days before a primer is applied. We do not recommend painting plaster before 30 days drying time. Quite often, in freshly plastered rooms, the high humidity can be felt. If after 30 days the humidity in the rooms is still extraordinarily high, more drying time is required to allow the water to escape from the plaster. After the plaster is dry, apply a coat of Aqua Borne Ceramic 3200-00 blockout/ enamel Undercoat Primer. This primer lays down to a very smooth finish and has excellent adhesion. Its 100% acrylic formula resists any lingering effect of high alkalinity. Any high-quality finish coat can be applied over the primer. We recommend two finish coats of Ultra Aqua Borne Ceramic Flat, Satin, or Gloss Enamel.
Since the surface of plaster is so smooth, we recommend using a short-nap roller such as a 3/8”, certainly no longer ½”, to minimize the marks left by the nap on the wall. Spraying is an ideal application method to preserve the smooth surface of the plaster.