New plaster must be fully dry and cured before painting. The drying time for plaster ranges from 1 to 4 hours, but the curing process can take more than five days, depending on various factors, including humidity levels, temperature, the amount of plaster used, and airflow in the area. You should always apply primer before painting plaster.

Drywall can be toxic to the environment and to humans in some cases. As drywall breaks down in a landfill and comes in contact with other organic chemicals, it can create hydrogen sulfide gas or leach into the groundwater. Additionally, the CDC recommends methods for controlling the inhalation of drywall dust when handled. While the common ingredients of drywall—gypsum, silica, and mica—are naturally occurring, they can cause irritation in some humans.

Plastering and skimming are two different techniques for finishing walls. Plastering involves applying a thick layer of a plaster mixture—typically containing gypsum, lime, cement, sand, and water—to create a new surface. This process often requires multiple coats and is used for repairing significant damage or creating decorative textures. Skimming, on the other hand, is a technique that involves applying a thin layer of drywall compound or joint compound over an existing surface to smooth it out, covering minor imperfections, small cracks, or uneven textures for a polished look. Plastering is generally more costly and labor-intensive than skimming. Although some people use the terms interchangeably, they refer to different processes and materials.

All plaster walls will crack over time due to normal house settling and expansion and contraction from temperature and moisture changes. Small, thin hairline cracks are generally not serious and are mostly a cosmetic issue. However, larger or more significant cracks can indicate structural problems.

Here's how to tell the difference:

• Cosmetic Cracks: Cracks that are 0.5 cm (0.2 inches) or thinner are typically cosmetic.

• Structural Cracks: Cracks wider than 0.5 cm, excessive or deep cracks, multiple cracks in the same area, or cracks that span around corners can signify a structural or foundation issue. Cracks along the joints where walls meet the ceiling also warrant attention.

For cracks wider than 0.5 cm, structural repair is needed. If a crack is 2.5 cm (1 inch) or wider, or if you notice any signs of a structural problem, it is best to contact a plaster repair professional to assess the damage.