How Long After Plastering Can You Paint?

Waiting for plaster to cure and dry out thoroughly can be frustrating, especially if you're keen to finish the decorating! However, you'll need to wait at least four days and sometimes upwards of a month before you can paint.

The key is to wait until the plaster is set completely in a soft pink colour without darker patches.

Once the plaster is ready to paint, you should remove the fine layer of dust and start with a mist coat mixing about 50% water with a skin of matte emulsion to prime the wall and seal the plaster.

Here we'll explain a little more about why plaster needs to dry, how long that's likely to take, and what happens if impatience gets the better of you!

Factors in How Long You Should Wait to Paint Over Plaster

Plaster can take a varying amount of time to dry, and this could be anything from four days up to six weeks for a thick plaster coat applied to raw brick or plasterboard.

There are a few ways to speed up the drying time, such as:

• Opening windows and doors to increase ventilation.
• Using a dehumidifier (on a low setting) to remove excess condensation from the air.
• Ensuring the heating is on at a normal level.

Heat lamps will undoubtedly mean the plaster dries quicker but can be detrimental as plaster that is forced to dry too fast can become brittle and crumbly - in which case you might need to start over!

It's never a great idea to apply paint to wet plaster because it won't bond properly and will usually start to peel away in strips. 

The lack of adhesion between wet plaster and paint also means that the paint doesn't 'stick', so you'll often see bubbles and blisters.

A mist coat, painted onto thoroughly dry plaster, is the ideal. Plaster is porous and sucks moisture from the paint, so painting neat emulsion directly onto the surface can mean the paint dries very fast, with an uneven finish.

Other Considerations in Painting a Freshly Plastered Wall

It's really difficult to say how long your fresh plaster will need to dry with accuracy. 

That depends on the surface material, thickness of the plaster, temperature of the room, and size of the wall or ceiling.

Thicker coats of plaster can take up to six weeks to dry out, so it isn't unusual to need a considerable wait until you're ready to paint. Multiple layers of plaster can even take two months to dry, so it's essential to keep an eye on the wall's colour and texture. 

Touch won't be sufficient since the plaster might feel dry but be damp towards the back of the application.

Once you're confident that the plaster is fully cured, you'll need to apply a mist coat - we'll explain the process below!

Why Apply a Mist Coat to a Plastered Wall?

Mist coats are made of normal emulsion paint, watered down to act as a primer for your newly plastered wall. The wall soaks up the extra water in the paint, which means you won't have a dry and cracked topcoat.

There are alternatives, such as water-based primers, but an emulsion mix is just as efficient and far more cost-effective.

Exact mist coat concentrations vary slightly depending on the type of paint you're using and how dry the plaster wall is, but most solutions are from 50/50 to three parts paint to one part water.

It's essential to check the manufacturer's instructions on the tin to ensure you get the right ratio.

The mist coat doesn't need to be applied with the exact paint you are using for your final topcoat, but a similar colour is advisable, so you get a nice, even finish.

How Long After a Mist Coat Can I Paint?

You can apply a mist coat with a roller or paintbrush but be warned that this thin liquid solution will splatter and drip very easily, so it's worth using a floor covering to minimise any drops.

The best application method is to use smooth upwards strokes, covering the entire wall. 

When you spot any drips or streaks, make sure to paint them quickly, as the plaster will be very absorbent and might make it hard to correct any dots of paint after they've dried out.

Once your mist coat is finished, you should wait up to 24 hours for it to dry thoroughly, but most thin mist coats of one layer take an hour or two tops.

It's essential to spend time on this preparation stage, even if you'd like to get the finished room ready to use.

Sanding down any imperfections, removing dust and leaving a good amount of drying time will all mean you get a perfect finish.