Painting on plaster or composite boards without sanding or priming properly result in irregular patches on the surface or opaque spots where the paint is not mixed properly. Using any type of paint on wrong basis can even cause bright spots on the paint finish. The same applies to the exterior plaster.

When using plaster

Gypsum (gypsum plaster) is one of several types of fillers. Others include joint compound or drywall, caulking, patching stucco and masonry and plaster of Paris. The plaster comes in a variety of ways. The lightweight gypsum is commonly used for interiors. It dries quickly, is not compressed and sands easily. The stress cracks or joints that expand and contract are best to fill them with a flexible elastomeric plaster. The vinyl plaster can be used outdoors and trim coating. All plasters are designed only for minor repairs and narrow crevices. Use the plaster properly will ensure a lasting repair.

Paint on interior plaster

If the repair is cast on a smooth surface you need to be sanded very flush so there are no ridges. Feel the rough to pass your hand over the repair. If the patch is in a plaster textured wall, no need to sand at all. Because the plaster patch is more porous than the surrounding surface, you have to be prepared before top coating; otherwise it will look like a dull point. No need to use a special primer; any water-based paint for general purpose or drywall will. Use any paint you would use to finish the job. Let it dry for about four hours before repainting. Avoid using primer to remove the stain of the patch. These are very dense and can make the place less absorbent than the surrounding wall. Instead of being a dull point, you can end up with a bright point. To achieve a final blend for a touch, use the same method of application used for the original surface. In other words, use a roller to paint a wall or a brush to the door that has been painted. Paint retouching extends beyond the edges of the patched site and slightly lowers the edges and mixed thoroughly.

Painting on exterior plaster

Because the outdoors is subject to direct sunlight and extreme temperature and humidity, the materials used to patch and paint the exterior of the home need to be more flexible and weatherproof. A common mistake that people make when using outside is neglecting plaster primer bare wood before plaster. The bare wood is moisture absorbent and filter from the patch, causing it to dry and crack. Place the wood primer, let dry and then apply the plaster. To paint on exterior plaster, use two coats of finish paint, leaving four hours of drying time between coats.