Cracks which appear before refinishing can be fixed by the painter before applying a final coat. Painter generally do not have problem with these typical cracks. However, cracks existing after coating cannot be cured using general water-based plastic paint as it lacks an ample elongation and is thus unable to conceal cracks. Cracks can be worsened when the downpours leak down into the surface. Consequently, this can cause blisters, fading and algae or mildew.
Causes of Cracks or Alligatoring
Improper dissolving of water during plaster mixing can enable the mortar to absorb moisture too fast. Other possible causes include applying plaster while room temperature is hot, the surface directly exposes to sunlight which dries the plaster up too fast, insufficient moisturising of plastered surface, as well as the expansion and contraction of plaster due to climate conditions.
Characteristics of Cracks or Alligatoring
The width of cracks is typically no larger than 0.2 mm. Cracks mainly exist on exterior plaster wall, either before or after refinishing.
Clean the surface thoroughly and leave dry. Prepare original surface with primer and refinish with coating paint that offers crack concealing quality. Twice coating will do. (To add capability in crack concealing, apply paint into cracks with brush for 1-2 times, and refinish overall surface twice).