How to Paint Fresh Plaster

How to Paint New Plaster

Painting a newly plastered or skimmed wall requires more preparation than painting an ordinary wall.

The plaster will first need to be sealed using a mist coat, which is essentially watered-down emulsion paint that acts as a primer. This is usually one part water to three parts paint, and it is often best to use white emulsion.

This gives your plaster something to absorb, so the actual top layer of paint will stick and not soak into the plaster.

The mist coat bonds with the plaster, giving the ideal painting surface. Many decorators recommend using an airless paint sprayer to add a mist coat to your walls. This is quick and much less messy than using a roller and brush.

You can then use the paint sprayer to apply the final topcoats. The sprayer pump just sits in the paint solution, so there’s no waste.

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Below is all you need to know about painting on fresh plaster, and mist coats.

 

How to Paint New Plaster with a Mist Coat

You will need:

• Mist coat (topcoat paint or cheaper decorators paint, watered down)
• Water
• Dust sheets
• Masking tape
• Airless paint sprayer
• Top coat paint
• Paddle mixer (optional)

 

When decorating and working with paint, always purchase and wear PPE. You will need eye protection, breathing protection, gloves, and clothes to cover your skin.

 

1. Let the plaster dry

If you’ve just plastered, always ensure it is fully dry before attempting further decorating. This could take anywhere up to a week.

Dry plaster will all be lighter in colour, the same colour on all parts of the wall, with no darker damp patches.

Painting before the plaster is properly dried will cause your paint to soak into the plaster, which could damage the plaster over time.

While the plaster is drying, prep your room for the painting. Use dust sheets on the floor, fixed with decorators’ tape. If you’ll be using a paint sprayer, you’ll also want to cover or remove any fixtures or fittings.

 

2. Mix the mist coat

Always follow the paint manufacturer’s instructions on this. They will likely be written on the tin. Ratios can vary, ranging from 10% water to 40% water.

If not, a guide is 1/4 water to 3/4 paint. Alternatively, you can purchase a water-based primer, but these can be pricy.

You don’t have to use the same coat you’ll be using as a topcoat, but the paint colour should be similar or plain white. A cheaper, decorator-quality paint can do the job—just check if it says it can be used as a mist coat.

Mix the mist coat in a bucket or old paint tub (clean it and remove any dried material first). Work out roughly how much you’ll need first so you don't waste anything. If using a paint sprayer, check that the pump will be able to sit in the chosen paint tub.

Mix the mist coat really well. You don’t want water sitting on the paint surface. A paddle mixer could help here.

 

3. Apply the mist coat

A paint sprayer will be easiest if you’ve prepared your room and covered everything.

Alternatively, a roller is the second-best bet. This will be more time-consuming, as you may need to transfer the mist coat mixture into a paint tray.

If you do use a roller or paintbrush, watch out for drips. Mist coats are very runny, so any mist coats should be quickly painted over to avoid drip marks drying.

 

4. Wait for the mist coat to dry

A mist coat should be left to dry for around 24 hours, even if it feels dry before this.

Only one mist coat should be needed, but if you have some paint leftover that’s already been watered down, you might want to add a second mist coat. As long as the first coat was dry, two mist coats will do no harm.

 

5. Apply the topcoat

As soon as your mist coat(s) has dried, apply the topcoat. You can use a paint sprayer here too.

For the best results, two coats of topcoat will likely be required. Wait until these dry for another 24 hours for the finished result.

 

 

FAQ’s

Why do I need a mist coat?

A mist coat acts as a primer. It seals the wall to create the ideal base for further emulsion layers.

Are you tempted to start painting without a mist coat? Don’t. The top layers of paint will not properly adhere to the plaster, and once dry, they will flake, crack, and peel.

This can happen while you’re decorating or the next time you go to paint, meaning you need to carry out repairs such as sanding and filling. Your paint could also bubble without a mist coat.

You’ll also need to use more paint to make up for the fact that it will soak in, which means that when it does inevitably flake away, you’ll be left with uneven walls. This means all your plastering efforts were wasted.

 

What can I use as a mist coat?

Most paint emulsion companies now advise that you use a watered-down version of the same product you will be painting with, but to save money, a lower budget trade-appropriate white emulsion is ideal if your paint is expensive.

The mist coat doesn’t need to cover the plaster or add colour. The aim is just to create an adhesive, non-permeable surface.

Alternatively, you can purchase water-based primers, which are suitable for use as mist coats. Paint companies often market these as Plaster Sealers. This could be less messy but will add additional costs to your budget as they're pricier than ordinary white emulsion.

Wait until the mist coat dries before resuming normal painting.

 

What ratio of water to paint is used on a mist coat?

The ratio of water to paint varies depending on the paint you’ll use. Most paint tins offer instructions on this, so always follow these. However, generally speaking, around 25% water and 75% paint is seen as ideal. Some say one-third water to two-thirds paint, even.

Issues are more likely to arise by adding not enough water than by adding too much water. So, always add more water if you’re concerned the consistency isn't any different.

 

Do I need to mist-coat old plaster?

Renovating? You may uncover old plaster underneath the wallpaper, which is still in good enough condition without needing to be skimmed. Once the plaster has been repaired, you will then want to paint.

You should still apply a mist coat to the old plaster. Old plaster is very dry, causing the paint to soak in and dry quickly. As you go on, this will cause roller or brush marks and an uneven finish.

So, mist coat as you would with new plaster, then use an airless paint sprayer to ensure you get an even finish again. Wait until it is completely dry before painting as normal.

 

 

READY FOR MORE DIY TIPS?

Thank you for reading our Speedy Hire blog on how to paint new plaster, with a guide on mist coats.

Read our blog on how to use a paint sprayer if you want some tips on the equipment before you begin.

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