How to Paint on Newly Plastered Walls
In this blog, we’ll talk about how to paint on newly plastered walls. We'll explain some of the techniques and technical terminology and take you through the process step by step.
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The groundwork is done, fresh plaster has been professionally applied, and your walls are smooth and sleek. It's over to you now; the room is ready to paint. Or is it? Before you apply your favourite Graham & Brown paint to the walls, there are a few things you need to know to get the best possible result.
In this blog, we’ll talk about how to paint on newly plastered walls. We'll explain some of the techniques and technical terminology and take you through the process step by step. With our help, you should be able to create a flawless interior that'll stay looking beautiful for years to come.
Can I paint straight onto new plaster?
The simple answer is no. Plaster has a high moisture content when it's applied, and to ensure your plaster not only stays on the wall but doesn't affect your decorating, it has to be allowed to dry thoroughly. So, you will need a little patience before you open up that tin of Resistance Ultra Matt emulsion paint.
The plaster doesn't just have to dry; it has to 'cure', too. This ensures that the whole application has had enough time to dry hard, not just the top surface layer. The curing time will depend on the type of plaster used and whether it's wet plaster applied to an existing surface or plasterboard. Plaster is a permeable material, so it readily soaks up moisture, and even condensation in the air will keep plaster wet.
The time of year your plaster goes up will also affect its drying time. If you don't want to wait weeks for it to cure properly, our first tip is to plaster your walls in the warm summer months when humidity is at its lowest and the air temperature is warmer.
Wet plaster takes up to four weeks to dry completely, but you can speed the process up by heating the room. However, don’t try to dry the plaster too quickly or you may find that it develops cracks. Plasterboard is already dry (hence its name ‘drywall’ in some countries) but should still be left for two or three days to settle in.
How do I know my plaster is still damp?
Plaster dries to a slightly chalky consistency. If you notice dark patches on the surface, that will indicate that some areas are still damp and the plaster needs a little longer to dry completely.
Why is it so essential to make sure the plaster is totally dry?
If you apply paint to plaster that isn't completely dry, it forms a skin over the plaster. This skin of paint won't adhere properly to the plaster and will quickly blister and flake off. You're essentially trapping the moisture underneath the paint layer by painting the surface while the plaster is still damp.
In the worst-case scenario, it could degrade the adhesion of the plaster and cause it to crumble away from the wall. So, a few days' patience ensures you'll get a long-lasting, professional-quality finish with no nasty surprises further down the line.
Preparing your wall for painting
Once you are absolutely sure your plaster is dry, it's time to prepare it for painting. Plasterboard doesn't need to be sanded down, but applied plaster may need some attention to create a smooth surface and remove any blemishes.
To do this, use P180-grit sandpaper and dry-sand the surface to achieve a completely smooth finish. Ensure you're wearing a mask and goggles for this and that any surfaces have been covered by dust sheets, as plaster dust can get everywhere. You then need to seal your plaster before painting.
How do you seal new plaster before painting?
This is the most crucial step when learning how to paint on newly plastered walls. You need to apply a 'mist' coat before you can add your topcoats. A mist coat is simply a coat of watered-down emulsion that seals the surface of the plaster and gives you a smooth primer coat. The mist coat is effectively your undercoat, so you don't need to apply anything beforehand.
How do I make a mist coat?
It's straightforward to make a mist coat. All you need is an emulsion paint similar in colour to your topcoat. You then dilute this with ordinary water at a ratio of about three parts paint to one part water (for example, 600ml of paint to 200ml of water). You can check on your paint can as some manufacturers will give you the exact amount their emulsion should be diluted by, but generally, a 3:1 mix will be suitable for most jobs.
You will need to stir it thoroughly so that the water is properly mixed in and there is no water sitting on the top of the paint.
Top tip: Plaster needs to be able to 'breathe' to allow any moisture to escape. So, use a water-based emulsion and not a vinyl-based paint.
This mist coat will be much thinner and runnier than your usual emulsion paint, so make sure you've prepared the room beforehand, as there is a good chance of splashes and spills. Cover surfaces (including the floor) with dust sheets and cover light sockets, trim and skirting board with masking tape to protect them from drips or runs.
You can tell if your mist coat ratio is off immediately. If it's too thin, it will drip and run as soon as you apply it to the surface. If it's too thick, the plaster won't absorb it. The consistency you're looking for is the same as thin cream. You can then apply the mist coat like you would with ordinary emulsion.
Top tip: Don't 'load' your roller or brush up too much, as you will end up chasing drips all day. The trick with a mist coat is to apply a little bit at a time and roll in an upward rather than a downward direction to prevent the paint from running. A smaller paint brush will allow you to get into any corners or to apply a thin edge along the skirting first.
Your mist coat will take around 24 hours to dry thoroughly.
Once your mist coat is completely dry, you can apply your topcoat. It may take a couple of coats to achieve the perfect result. However, by spending a little extra time at this stage, you can create a smooth and flawless finish.
And that’s all there is to it! If you’ve been wondering how to paint on plaster for the first time, this should have answered all your questions. Remember, it's all about patience and thorough preparation. Let the plaster dry completely, don't skip the mist coat, and take your time, and you'll be enjoying a world of colour, thanks to Graham & Brown's beautiful paints.