How to cure Plaster Grinning

Grinning is the term given to the appearance of a plastered wall when the positions of the mortar joints are clearly visible through the plaster. It is caused by the difference in suction between the masonry units and the mortar. Raking out mortar joints also causes grinning and the practice should thus be limited to soft clay brickwork. 

While grinning may be unsightly, it is unlikely to lead to further cracking. The only option to cure Plaster Grinning is to live with it, or to remove and replace the plaster. Application of an undercoat or a spatter-dash coat before plastering will help to avoid grinning.