Painting New Plaster
Most new plastering today is done in gypsum – often known as pink finish. There is also however, a rapidly growing use of traditional lime plasters, once thought only necessary in period buildings but increasingly valued for its ability to accommodate movement without cracking. In both cases the surface of the plaster is highly absorbent when new. As the plaster dries, a ‘sinter skin’ forms as the binder migrates to the surface. In modern gypsum plasters these can be quite variable, especially if the plasterer has trowelled the plaster hard to get a very smooth finish. This calls for care in preparing it for painting as it may result in areas of widely differing absorbency.
The first step is ALWAYS to work out what you are dealing with.
Does the plaster look dry (pale pink, if gypsum)?
Does it look shiny (polished to be silky smooth, but will be less permeable)?
Remove the sinter skin by thoroughly rubbing down with standard grade sandpaper all over. Remove the dust and wash down the wall to neutralise the surface.
There are two ways to give the plaster what it then needs – a primer, or a mist coat. We recommend using Plaster Primer as it is a cost-effective method to take up the absorbency of the plaster, it is diluted 50:50 in order to draw the right amount of binder into the plaster surface. Observe how the plaster behaves – if it sucks the primer in unevenly this is what will happen with the paint layers and you may find you need three coats for full obliteration with white paint over pink finish.
Our premium white emulsion has the highest opacity rating, but this does not guarantee that it will obliterate the pinkiness of gypsum plaster in 2 coats in all cases. The coverage is dependent on the way the plaster and paint is applied.
Posted: October 2019