How Long Does a Mist Coat Take to Dry?

Today we'll explain some of the factors that affect a mist coat application, the benefits to building in sufficient drying time, and how you can speed up the process!

Factors Impacting Your Mist Coat Drying Time

There are many things that can mean your mist coat; the first coat of paint you apply to freshly applied plaster takes to dry.

The layer is designed to prime the wall or ceiling and act as a seal, as a perfectly smooth base for applying the next coat of emulsion.

We'll talk about the benefits shortly, but a poorly applied mist coat, or one that hasn't dried properly, can mean your paint finish is inadequate and doesn't adhere properly to the bare plaster, causing peeling.

The biggest factors in mist coat drying times are:

• The heat and ventilation in the room.
• The thickness of the mist coat.

A regular room at normal temperature will allow the mist coat to be thoroughly dry in around two hours. 

Still, if you're working in the winter, a damp property, or a space with low ventilation, it's important to wait a little longer to avoid any problems.

Other Considerations When Applying a Mist Coat

While a warm room and open windows can speed up your mist coat drying times, other factors come into play.

First, let's talk about dilution ratios - a mist coat is typically a mixture of water and emulsion, and the combination will depend a little on what sort of paint you use.

There isn't one suitable solution ratio for every project:

• A bathroom or kitchen, which is more prone to peeling because of humidity, often has a mist coat with a higher water ratio of 50-60%. This solution will be looser, so it's vital to cover flooring and furnishings to protect against drips.
• Paint designed for use on plaster can be thicker, with a typical 10-20% paint to water ratio.
• A vinyl emulsion should be mixed at about 25% paint to 75% water, although you'll need to dilute your mist coat further for an eggshell colour.

Generally, it's far better to use too much water than too little.

Choosing the Right Paint for a Mist Coat Mixture

Next, the type of emulsion used in your mist coat will impact the drying time and the finish.

Most decorators use standard matt paint, which is cheaper than vinyl and less flexible, making it less prone to peeling. Rather than forming a skin, like a vinyl emulsion, matt soaks in better.

You can use acrylic, which has a little more protection from dampness, but imperfections may show as the slight sheen highlights any tiny bumps. 

Diamond matt is a higher-end option, which is more expensive but delivers a tough, hardwearing finish without the shiny finish you'll get from a vinyl emulsion.

Making Sure Plaster is Dry Before Applying a Mist Coat

The final factor is to check that the plaster is completely dry before starting with your mist coat application.

Plaster that is still slightly damp isn't ready to paint and will cause peeling - wait until the application is a pale colour, without any patches.

It can take around three to six days for a standard layer of plaster to dry and possibly longer for deeply plastered areas or colder properties.

Thick plaster can even take up to four weeks to be dry, and again this process depends on how damp the room is. Many plasterers use heat lamps or added ventilation to speed up the process.

If you're plastering in an older property following a damp proof course, the old plaster will have been removed right back to the brickwork, with two backing coats before the final plaster skim, so it needs longer to dry.

Skimmed plaster, which is a finish to refine the surface texture of the wall, is much thinner, often used to cover up Artex - this will dry faster since the plaster is much less dense.