Choosing the right paint ensures a smooth and lasting finish when painting newly plastered walls. The first coat you apply to freshly plastered surfaces should be a “mist coat.” If you’re unsure about a mist coat, don’t worry—we’ll explain. This guide will help you understand the importance of a mist coat, the best paint type, and common mistakes to avoid when painting over new plaster.
Let’s get straight to the point.
Always use a mist coat—a diluted water-based matt emulsion paint when painting newly plastered walls. This helps the paint bond with the plaster and prevents peeling. Avoid vinyl, silk paints, and PVA sealants, as they create barriers that prevent proper adhesion. Make sure the plaster is completely dry before applying any paint, and use a light neutral colour for the mist coat to create a good base for your final colour. Apply at least two coats of standard emulsion paint for the best finish.
What Is A Mist Coat?
A mist coat is the first layer of paint applied to new plaster. It differs from regular paint because it is diluted with water, which helps it penetrate the porous surface of fresh plaster more effectively. The purpose of the mist coat is to create a solid bond between the plaster and subsequent layers of paint.
Why Is A Mist Coat Important?
New plaster is highly absorbent, and with a proper first coat, the plaster can absorb less paint, resulting in an uneven finish. A mist coat solves this issue by sealing the plaster and providing a smooth base for additional coats of paint. This method also helps the plaster “breathe,” which is crucial for preventing moisture build-up beneath the paint, which could lead to peeling or other damage.
Choosing The Right Paint For New Plaster
When selecting paint for new plaster, choosing the right type of paint is important to ensure durability and a quality finish. Here are the key considerations:
1. Water-Based Matt Emulsion Paint
The best choice for the mist coat is a water-based matt emulsion paint. This type of paint is commonly available in most hardware and home improvement stores. It is an all-purpose paint that is easy to work with, dries quickly, and adheres well to plaster. The water-based formulation is essential for ensuring that the paint bonds properly with the plaster without forming a seal that could prevent further layers from sticking.
2. Diluted Matt Emulsion
To apply the mist coat, dilute the matt emulsion paint with water. The recommended dilution ratio is typically 70% paint and 30% water, although this may vary depending on the manufacturer’s instructions. The diluted paint will absorb into the plaster better and create a solid, breathable base layer.
3. Why Avoid Vinyl And Silk Paints?
It’s crucial to avoid using vinyl or silk paints on new plaster. These paints may seem like a good option, but they create a barrier on the plaster’s surface as they dry. This “skin” can stop the paint from bonding properly, causing the paint to flake or peel over time. Vinyl and silk paints don’t allow the plaster to breathe, which can lead to trapped moisture and long-term damage.
4. PVA (Polyvinyl Acetate) Sealant: A Mistake To Avoid
Some people recommend using PVA (Polyvinyl Acetate) to seal newly plastered walls before applying paint. However, this is not advisable. While PVA acts as a waterproof barrier, it prevents the plaster from absorbing paint properly. Applying PVA will stop the mist coat from bonding with the plaster, making it more difficult for the paint to adhere to the surface and leading to peeling or flaking in the future.
Best Practices For Painting New Plaster
To ensure the best results when painting new plaster, follow these key steps:
1. Prep The Surface Thoroughly
Before you start painting, make sure the plaster is completely dry. Depending on the thickness and humidity levels, fresh plaster can take several weeks to fully dry. Applying paint to damp plaster can cause moisture to become trapped, leading to paint failure.
Also, check the plaster for imperfections or rough spots. Use fine-grade sandpaper to smooth out any bumps or uneven areas. Cleaning the wall is also important—ensure no dust or debris is left on the surface.
2. Apply The Mist Coat Correctly
Once the plaster is dry and prepped, it’s time to apply the mist coat. As mentioned, dilute the matt emulsion with water to a 70:30 ratio. Use a brush to apply the mist coat around the edges and a roller for the rest of the surface. Make sure the coat is even and covers the entire wall.
3. Allow The Mist Coat To Dry Completely
After applying the mist coat, allow it to dry for several hours or overnight, depending on the manufacturer’s drying times. The mist coat should be fully dry before applying the next layer of paint. If the mist coat is not completely dry, subsequent coats may not adhere properly.
4. Apply Additional Coats Of Paint
Once the mist coat has dried, apply your top coats. For the best finish, use standard emulsion paint for the next layers. You can choose a matt, satin, or gloss finish, depending on your preferences. Typically, two or more coats of standard emulsion paint will be needed to achieve full coverage and an even finish.
What Colour Should The Mist Coat Be?
For the mist coat, it’s recommended to use a light neutral colour—preferably white or a very light grey. This makes a great base for any overcoat colour you plan to use. Lighter shades provide better coverage and make it easier to apply additional coats of paint in your preferred colour.
Common Mistakes To Avoid When Painting New Plaster
There are several things that homeowners and DIY enthusiasts often need to correct when painting new plaster. Here are some of the most common ones to watch out for:
1. Skipping The Mist Coat
Some people make the mistake of applying regular paint directly to fresh plaster. This can lead to poor adhesion, peeling, and uneven coverage. Always apply a mist coat before your top coats.
2. Using The Wrong Type Of Paint
As mentioned earlier, using vinyl or silk paints on new plaster is a major mistake. These paints form a barrier that prevents the plaster from breathing, which can lead to problems down the line. Stick with water-based, matt emulsion paint for the mist coat.
3. Not Allowing The Plaster To Dry Completely
One of the biggest mistakes you can make is painting over plaster that isn’t fully dry. Moisture trapped beneath the paint can lead to bubbling, peeling, or other issues. Be patient and wait for the plaster to dry thoroughly before applying paint.
4. Applying Too Many Coats Too Quickly
Another mistake is applying multiple coats of paint quickly before the previous coat has dried properly. Each coat needs time to set and dry before the next one is applied. Rushing the process can result in a patchy, uneven finish.
Conclusion
When painting newly plastered walls, the first step is to apply a mist coat using water-based, matt emulsion paint diluted with water. This creates a strong bond with the plaster and provides a solid base for subsequent layers of paint. Avoid using vinyl, silk paints, or PVA sealants, as these can prevent the paint from adhering properly and lead to long-term issues like peeling or flaking.
By following the correct procedure and using the right type of paint, you can ensure a smooth and durable finish that will last for years. Remember to be patient, allow each layer to dry fully, and choose the right colour for your mist coat to ensure the best results.
FAQs About Painting Newly Plastered Walls
What Is A Mist Coat, And Why Is It Necessary For Newly Plastered Walls?
A mist coat is the first layer of diluted paint applied to new plaster. It helps the paint bond to the porous surface of the plaster and prevents issues like peeling or uneven coverage. The paint can absorb too much into the plaster without it, leading to poor results.
Can I Use Regular Paint Directly On The New Plaster?
No, it would be best not to use regular paint directly on fresh plaster. A mist coat is essential because it seals the plaster and creates a stable base for subsequent layers of paint. Regular paint without a mist coat can result in poor adhesion and peeling.
What Type Of Paint Should I Use For The Mist Coat?
The best option for a mist coat is water-based matt emulsion paint. This type of paint is highly recommended for new plaster because it bonds well and allows the plaster to breathe. Avoid using vinyl or silk paints, as they don’t adhere properly to the surface.
How Do I Apply A Mist Coat To A New Plaster?
To apply a mist coat, dilute water-based matt emulsion paint with water (usually 70% to 30% water). Use a brush to paint the edges and a roller for the larger areas. Allow the mist coat to dry completely before applying any additional coats of paint.
Can I Skip The Mist Coat If I’m In A Hurry?
It’s strongly recommended that you do not skip the mist coat. Without it, your paint may not bond properly to the plaster, leading to an uneven finish or peeling over time. Taking the time to apply a mist coat ensures a more durable and professional-looking result.
