How to Paint New Plaster

How to Paint New Plaster

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

The plaster will first need to be sealed using a mist coat. A mist coat is essentially watered-down emulsion paint.

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. The best way to add a mist coat to your walls, as many decorators would recommend, is to use an airless paint sprayer. This is quick and will be a lot less messy than using a roller and brush.

You can then use the paint sprayer to add the final topcoats of paint, too. 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. Eye protection, breathing protection, gloves, and clothes to cover your skin will be needed.

 

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 plaster is properly dried will mean your paint just soaks into the plaster and could cause damage to the plaster over time too.

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 and range from 10% water to 40% water. Alternatively, purchase a water-based primer.

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

Use a bucket or old paint tub to mix the mist coat. Work out roughly how much you’ll need first. If using a paint sprayer, check 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, and you’ll 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 layers of emulsion.

Tempted to just start painting without a mist coat? Don’t. The top layers of paint will not properly adhere to the plaster, and once dry, it will just 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.

You don’t need the mist coat 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 to use as mist coats. This could be less messy but will add costs to your budget.

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 is seen as ideal. Some say one-third water to two-thirds paint, even.

If instead, you’re using a cheaper emulsion to save money, you may want to stick to around 10%-20% water. If you do use a cheaper emulsion, ensure it is a similar plain colour to the topcoat which will help it look 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.

 

Do I need to mist-coat old plaster?

Renovating? You may uncover old plaster underneath the wallpaper, which is still in good enough condition. Once the plaster has been repaired, you then will want to paint.

You should still apply a mist coat to old, dry plaster. Old plaster will be very dry, causing the paint to soak in and dry quickly too. 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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