Painting freshly plastered walls isn’t as simple as opening a tin of emulsion and getting stuck in. Before you go anywhere near a brush or roller, you need to apply a mist coat. This essential step helps your topcoat bond properly and ensures your beautifully smooth plaster doesn’t end up cracking or peeling.

In this guide, we’ll explain what a mist coat is, how to make one, and why skipping it can cost you more time and money in the long run.

What Is a Mist Coat?

A mist coat is a diluted layer of emulsion paint, usually mixed with water and applied directly to bare plaster. Its job is to seal the porous surface of the plaster so that your final coats of paint can properly adhere.

Fresh plaster is incredibly absorbent. If you paint directly onto it with undiluted paint, the moisture is sucked out too quickly. This leads to cracking, flaking, or uneven coverage.

It acts like a primer. It soaks into the plaster, creates a binding layer, and gives your topcoats something to grip onto.

Why Is It Important?

Here’s why skipping this crucial step is never a good idea:

• Better paint adhesion – The mist coat bonds with the plaster and creates a surface that holds paint well.
• Smoother coverage – Your topcoat glides on more evenly, with fewer roller marks or patchy areas.
• Reduces paint waste – Without a mist coat, plaster soaks up paint like a sponge. You’ll end up using far more.
• Prevents future flaking or peeling – A strong foundation means longer-lasting results.

Whether you’re DIY-ing or hiring a professional decorator, using a mist coat is a non-negotiable step.

How to Make a Mist Coat

It is a simple process to make. All you need is:

• A non-vinyl, matt emulsion paint (avoid silk or vinyl paints)
• Clean water
• A bucket for mixing
• A roller and tray (or a large brush for edges)

The standard ratio:

• 70% paint to 30% water

Mix the emulsion and water thoroughly until you have a smooth, pourable consistency. It should be thinner than regular paint but not watery.

If your plaster is still slightly damp (but not wet), you might use a slightly thinner mix, like 50/50. Just make sure it soaks in well.

When Should You Apply a Mist Coat?

Timing is crucial. Plaster must be completely dry before you apply a mist coat. This usually takes 5 to 7 days for skimmed walls in good conditions, or longer if the plaster is thick or the room is cold and damp.

How to check:

• The colour should be light and even (no darker patches)
• The surface should feel cool but not wet to the touch

Applying too early traps moisture in the wall, which can lead to damp or mould issues later.

For more on this, see our full guide on How Long Plaster Takes to Dry.

How Do You Apply It To Plastered Walls?

Once mixed and the plaster is dry:

1. Stir the mixture well and pour into a tray
2. Use a brush for edges and a roller for large areas
3. Apply in long, even strokes
4. Let the mist coat dry completely (usually 12–24 hours)

Don’t worry if the mist coat looks patchy—that’s normal. Its job is to soak into the plaster, not provide full coverage. Once dry, it will leave a slightly chalky finish, ready for your topcoat.

What to Do After the Mist Coat

Once your mist coat is dry, lightly inspect the surface. If it feels rough, you can gently sand it with fine sandpaper. Then:

• Apply 2 topcoats of your chosen emulsion
• Let each coat dry fully before applying the next
• Use painter’s tape for sharp lines and clean edges

With proper prep, your walls will look crisp, clean and professional.

Professional Help for Flawless Results

If the idea of mixing ratios, waiting days, and getting the timing right feels overwhelming, hiring a decorator can save you time and stress. At LWM Plastering, we handle every step—from prepping fresh plaster to the final brush stroke.

We know exactly how to treat each surface, which paints to use, and how to deliver a durable, picture-perfect finish.

A mist coat may seem like a small step, but it’s essential for protecting your plaster and getting a professional-quality result. Whether you’re painting yourself or booking a decorating team, don’t skip this part of the process.

Need help preparing or painting your freshly plastered walls? Contact us for advice or to book a quote.