After plastering a new surface, nothing would be more disappointing than painting it badly. That is why knowing how long plaster takes to dry is very important.
How long does it take for the plaster to dry?
New plaster will need to be fully cured and dried prior to painting. The colour will change from a dark pink to light pink, and the time it will take to dry will depend on the thickness of the plaster, the temperature within the building, and the amount of ventilation available.
If the plastering has been carried out to an old property following the introduction of a chemical damp proof course, the plaster system used will include removal of the old plaster back to stone or brick, and 2 backing coats of sand and cement prior to the final plaster skim.
This system is carried out to replace plaster contaminated by hygroscopic salts (which will occur due to the action of rising damp) and will take considerably longer to dry out and cure, depending on the thickness of the masonry, and the thickness of the rendering/plastering system. You should seek some professional advice from a damp course specialist if you have any concerns about damp.
If the plastering has been carried out as a ‘skim’ to finish new plasterboards, or cover up/encapsulate artex, the drying times will be considerably quicker than the above application.
How To Speed up the drying process
The drying out of the new plaster will be enhanced significantly by increasing ventilation to the area- by opening windows and doors, and the introduction of a dehumidifier will help to remove moisture in the atmosphere.
The introduction of heat must be considered with caution, and low background heating is preferable to turning the heating system up high, which can dry the plaster out too quickly and cause cracking.
Preparing Plaster For Painting
When dry, new plaster will have a thin layer of dust on the surface. Brush this off prior to applying any paint. When the plaster is fully cured and dried, it is essential that a thinned down coat (65% paint/35% water) of a non-vinyl emulsion is applied.
This is called a ‘mist coat’, and will soak into the new plaster to form a key or primer prior to the application of the proposed paint system. The mist coat should be applied as evenly as possible, and allowed to fully dry.
At this stage, some minor surface filling may be required- any imperfections in the plastering will show up following the mist coat. Pay particular attention to corners, around electrical fittings, etc, where the plasterer may have experienced some difficulty with finishing due to getting trowels into tight areas. So fill and abrade using a fine filler and sandpaper, and mist coat any filled areas.
Prior to applying the final coats of paint, now is the time to caulk the corners.
Painting Over New Plaster
Consider the colour scheme prior to mist coating, as it will be preferable to mist coat in the same colour as the final coats to help build up to full opacity.
A possible problem with applying paint to new plaster is that the plasterer has over trowelled or polished the plaster. This will be noticed on the application of the mist coat, which will sit on the surface of the new plaster, possibly forming ‘bubbles’ and will not soak in to form the key/primer. In this case, it will be essential to thoroughly but lightly abrade the surfaces to roughen them, which will allow the paint to soak in.
Use fine sandpaper in this instance, so as not to scratch the surface too much, as the scratches will show up following the application of the final coats.
Following the successful application of the mist coats, and filling/light sanding has been carried out, the surfaces are now ready for the final paint coats.
A minimum of 2 coats will be required to achieve full opacity and should be applied as evenly as possible, using a clean medium pile roller head. If the paint is very thick, thoroughly mixing in half a cup of clean water into the paint will help the application to be easier to apply, and reduce patching to the final coats.
The decorators at Wall2Wall are experienced in painting new plaster on a regular basis. Please call us on 01793 435141 if you would like to discuss painting new plaster. We are more than happy to offer to advise, come and see you to discuss your project, and offer an obligation free quotation if required.