After plastering a new surface, nothing would be more disappointing than painting it badly. That is why knowing how long plaster takes to dry is very important.
While it can be tempting to start applying paint once all the walls have been plastered, it’s important to give that surface some time to cure before you apply paint. PVA-based plaster swells as it dries, and if your new paint is applied before this has happened, it can leave an undesirable finish the first time you walk into your room.
When to paint new plaster
It’s tough to know when to paint over new plaster. Wet plaster looks earthy with hints of brown, red or dark pink. Dry plaster is light creamy pink with no dark spots. Ideally, plaster needs to be fully dry prior to painting. It will take 4-6 weeks for fresh plaster to completely dry. Because fresh plaster is porous, it will absorb moisture. If you try to paint over wet plaster, the paint will most likely peel off.
How to paint new plaster
New plaster needs to be properly prepared before painting. If you aren’t familiar with proper preparation, following these few steps will help you get it right.
What you’ll need:
- Emulsion for the mist coat
- Water
- Dust sheets
- Decorator’s tape or masking tape
- Topcoat paint
- Paintbrush or roller
Leave the plaster to dry
Drying new plaster is a very important part of the job. If it is not done properly, then the result will be dry and lumpy. It will cause your paint coat to flake off and lose its protection against weathering. The solution is to wait till it dry completely before you apply any topcoat.
Mix your mist coat paint
Mix your mist coat paint in a medium-sized pail. Mixing it in a plastic pail will protect the plaster from getting chipped and scratched. To get a smooth finish, start by pouring the first coat of paint into a medium-sized pail, and using water-based paint, mix it well with a wooden paddle or plastic spatula. Make sure you create an emulsion with the paint, cleaning any bubbles on the surface before applying it onto the new plaster.
Apply your mist coat paint
Use a wide, soft brush to lay on the mist coat with broad strokes. Try not to use thin paint in your mist coat as this will leave dry pockets behind and will generally make your plaster appear drippy or beer-stained. The purpose of the first coat is to put down a very thin, even coat of paint. The first coat should be thin enough that you can see the texture of your wall through the paint layer, usually, one to two coats are all that is required for the first coat.
Paint your walls with a top coat
The final part of painting new plaster is the most exciting. And that’s applying your top coat and that all-important splash of colour. After you’ve completed all of the prep work, you can now paint your wall and design your space as usual.
What do I do if I have painted my new plaster too early?
This is rare, but we have seen this issue before. We recommend waiting as long as possible to paint your new plaster walls. If you do determine that you painted too early, simply scrape away the paint with a plastic putty knife. This is sometimes necessary with certain paints and textures.
Can you paint on fresh plaster?
Because fresh plaster is so porous, any moisture will quickly absorb into the wall. This is why your first paint layer should be watered down (known as a mist coat). To allow any moisture to escape, fresh plaster must be able to breathe beneath the paint, thus choose a non-vinyl water-based paint.
How can I speed up plaster drying?
We know how frustrating it is waiting for the plaster to dry, and we want to help. The key to fast-drying and preparing plaster to paint is patience. Plaster spreads best when the consistency of the mix is not too thick, so measure carefully and add water as necessary.
Also, the drying out of the new plaster will be greatly aided by increasing ventilation to the area by opening windows and doors, as well as the use of a dehumidifier to remove moisture from the air.
What is the best paint for a newly plastered wall?
When applying paint to newly plastered walls, you need paint which dries quickly and is breathable for an even finish. This will allow moisture to escape, preventing mould formation. The ordinary white emulsion will suffice, as it is both inexpensive and readily available. Many white emulsion paints will have a mist coat ratio printed on the tub.
Start misting at the bottom of the plaster and work your way up and out with your roller. The mist coat dries quickly, and the bottom-up procedure prevents large paint splashes on the plaster. With a brush, cut in around the edges of the entire wall of the house.
What happens if you don’t do a mist coat?
A mist coat is used to prime and seal a wall or ceiling so that additional coats of an emulsion can be applied. You risk adhesion troubles and paint failures if you skip the mist coat The idea of a mist coat is it will soak the pigment in otherwise it just forms a skin on the plaster,
If you’re going to utilise an emulsion as a mist coat, you’ll usually add a lot of water to it. Depending on the paint you use, the water-to-paint ratio varies slightly. If you’re using a low-cost contract matt or a paint made expressly for bear plaster, 10 percent to 20% water is quite acceptable (1 or 2 parts water to 10 parts paint). It is recommended to use more water than this for most products.
The water content of a vinyl mat, for example, should be around 25%. As a mist coat, some acrylic eggshells or soft sheen emulsions can be used, but they must be diluted even further.
Always read the manufacturer’s directions before proceeding, but add a little more water than they recommend. There are a lot of problems caused by not using enough water in a mist coat, but none from using too much. It’s always preferable to be safe than sorry!!
Do I need to prime plaster before painting?
Before painting new plaster, it must be primed. This is called a ‘mist coat’, and will soak into the new plaster to form a key or primer prior to the application of the proposed paint system. Freshly plastered walls are extremely dry, which will draw moisture from your paint. Using a mist coat to prime the walls will ensure you get a nice paint finish that won’t flake or peel. Contractors often worryingly think PVA will work as a sealer. Do not use PVA. This allows the initial coat to properly soak into the plaster aiding adhesion of the final coat.
How do I know when plaster is dry enough to paint?
A week should be enough time to properly let the plaster dry out and remove any damp patches. When the plaster is dry, it should be light in colour with no dark patches and consistent colour. If you use a heater or open a window, your plaster will dry faster.
Should you use a dehumidifier to dry plaster?
Using a dehumidifier to dry plaster is not recommended. This interferes with the natural drying and curing of plaster. When you use a dehumidifier to speed up the drying process, the plaster can begin to crack instantly or over time.
It also doesn’t have a gentle drying system. The dehumidifier’s air is excessively dry, and it might damage other materials, especially if you have wet insulation or wood in your walls that this machine will also dry.
Proper site management and insulation are the greatest ways to avoid experiencing humidity problems during construction.
Bottom line
Painting after plastering can be a tricky business especially if your wall is not completely cured. Taking into account that all walls take a different amount of time to completely dry (from 1 day to over 6 weeks) and all paints are not the same.
While you could paint over wet plaster before it has hardened, doing so could cause the second coat to never set correctly, which could lead to peeling, cracked paint or even mould growth.
However, make sure that your paint is water-resistant and somewhat flexible. Some people will also put on a clear coat finish so that even if there are small cracks or chips in the plaster, the paint will not peel away.
