What ratio of water-to-paint for new plaster? You'll find a few different ratios of water-to-paint floating around online when it comes to your mist coat. However, a common ratio is 3:1 – 3 parts paint to 1 part water.
All you need to do is dilute some emulsion paint with water and apply it to the plaster using a roller, paintbrush or spraying. One mist coat should suffice, but you can apply a second (or even third) coat just for extra peace of mind. That way, you can rest easy knowing that the plaster is sealed.
Mix your mist coat paint
All you need to do is get some white emulsion paint and thin it out with water – it's that easy! Ten parts paint to one part water should work. If you don't fancy watering down your paint you can also use Dulux Sealer for Plaster.
While there is a great deal of conflicting advice on which ratio of water to paint is best for painting plaster, we advise anything from two parts water to eight parts emulsion paint, down to 50/50 to ensure success – check the manufacturer's tin for the requirements for your specific brand and feel free to add more ...
New plaster is a really permeable surface (which simply means it will soak up any moisture really quickly!) So watering down your first coat as a 'mist coat' will help the plaster to soak up the paint and create a bond between the new plaster and the paint.
Too little water, and the paint would be thicker and less pliable. You'd be unable to get it onto your brush, much less apply it to the outside of a home. It's helpful to think of the water in paint as the delivery mechanism that carries the pigment in paint to the surface being painted.
Mix up a mist coat
New plaster is porous, so if you paint it with standard paint it will simply be absorbed by the wall. This means you'll need to apply more coats of paint, and the paint could start to peel later as it dries. To prevent this happening, you need to apply a mist coat first.
Similarly, mixing the plaster with too much water can make it overly soupy, which will make it difficult to hold on to the hawk and will cause the plaster to be spread too thinly. or a spatula down the center of the plaster in the bucket. If the plaster caves in on itself instantly, it may be too soupy.
For instance, if the plaster you're painting is thoroughly dry, it's a good idea to thin down the paint. It makes paint goes on better, and it will soak into the plaster better. To thin down emulsion ready for spraying, the best ratio is 70/30. That is 70% of paint and 30% water.
Too Much Water
You don't want to be too thin, but a mist coat needs to be thin—almost like a soup. The water will not seep into the substrate if the mist coat is too watery.
Fresh plaster is porous and will therefore absorb moisture. If you attempt to paint over plaster that is still damp the paint is likely to peel off. This is obviously not ideal! We really recommend holding yourself back and waiting before painting your new plaster.
There are a wide range of reasons paint can peel, including the surface being damp, salt migrating through the plaster causing the paint to peel or the surface not being completely clean before painting.
For single-coat plaster, a 1:4 ratio (1 part cement to 4 parts sand) is commonly used. This ratio provides sufficient strength and durability for surfaces that only need one layer of plaster.
Next the plaster is going to need a sealer coat applied, as new plaster is very porous. The traditional method of doing this is to thin out your 1st coat of emulsion by about 30 to 40% with clean water, making a sealer coat. This will penetrate deeply into the surface stopping any flaking off later on in years to come.
While some may suggest plastering and painting on the same day, it's essential to allow the plaster to cure before applying paint. Waiting for the plaster to dry completely, typically for around two weeks, allows all moisture to evaporate. This helps prevent issues such as paint peeling in the future.
"Hi there, if it is new plaster you are painting on for the first time, you will need to give it a mist coat first, 50/50 water and paint. Allow a few hours before. Apply the first coat of colour the again in 24 hours."
Mist coat paint is simply watered-down emulsion paint, which acts as a primer. All you need to do is get some white emulsion paint and thin it out with water. Three parts paint to one part water should do the trick.
If you water down paint too much then you will apply thinner coats, and it won't have the same covering power. You will need to apply additional coats.
What ratio of water-to-paint for new plaster? You'll find a few different ratios of water-to-paint floating around online when it comes to your mist coat. However, a common ratio is 3:1 – 3 parts paint to 1 part water.
How much water do I add? The water/plaster ratio is referred to as consistency. It is expressed as parts water per 100 parts plaster. Typical consistencies for Pottery Plaster (K60) range from 60-75 (60-75/100).
Curing Of The Plaster
Cement plaster needs at least 24 hours to cure after application. For the first seven days after plastering, the surface should remain damp. In addition, wait seven days before applying a second layer. For at least five days, each coat must be kept wet continually.
Let the plaster dry
Your plaster will dry quicker with a heater or if you open a window. If you try to apply paint to wet plaster this can cause adhesion problems. Applying emulsion to wet plaster also means that it may not bond properly and you could find that it peels off your wall.
New plaster is very permeable , which means it will absorb liquid i.e. paint. To stop this happening a mist coat is applied directly to new, fully dry plaster to help seal it ready for the top coat. This is effectively a watered down emulsion.
When it comes to painting over new plaster, you'll technically want three coats of paint – our two recommended coats plus a mist coat. A 'Contract matt' is specially designed for use on new plaster.
Before painting on newly skimmed walls, you'll need to wait until the plaster is completely dry. In good conditions – typically in summer months – this will usually take around three days. However, we'd recommend leaving it for at least two weeks if possible to be safe.