How To Paint New Plaster

Why New Plaster Needs Special Treatment

When painting on to new plaster, understand that fresh plaster is vastly different from a standard painted surface. New plaster is highly porous, which means it absorbs moisture quickly, leading to poor paint adhesion and uneven patches if untreated. If you go straight to applying a topcoat on fresh plaster, you may see blotchiness, bubbling, or even peeling over time.

You must use the correct process in preparing the plaster, ensuring it’s properly sealed and primed before you even think about applying a topcoat. The base coats, particularly the mist coat, provide the foundation needed to achieve a smooth, professional result when painting new plaster.

Curing and Drying Times for Fresh Plaster

Before tackling how to paint fresh plaster, it’s important to ensure the plaster is completely dry. Curing and drying times vary based on factors like plaster thickness, type, and room conditions. Here are some general guidelines, that must not be taken as gospel:

Thin Layers Of Plaster

Light, skimmed surfaces usually need about a week to dry thoroughly.

Standard Thickness Plastering

Newly plastered walls with standard application thickness typically require 2-4 weeks.

Deep or Thick Plastering

For very thick plaster, drying can take up to 6 weeks.

Knowing how to tell if plaster is dry enough to paint is crucial. Dry plaster should be a uniform, pale pink or light grey. If it’s darker in patches, it likely still contains moisture. Painting over damp plaster traps moisture, which can eventually cause flaking, bubbling, or blistering on your painted wall.

Mist Coat Preparation and Application

A mist coat is an essential first step when painting on plaster. This thin, watery coat is designed to soak into the porous surface of new plaster, creating a bond between the plaster and the paint layers. However, specialist primers, designed to seal new uncured and cured plaster, 

What is the Mist Coat Ratio?

The ideal mist coat ratio varies depending on which product you use. Other online guides to painting plaster that we have seen stipulate an 80/20 ratio of paint to water, others a 50/50 split. I asked Nick, Technical Accounts Manager at Rawlins, what the correct ratio is for a mist coat on new plaster:

 

How to Apply a Mist Coat

Once you’ve checked the recommended thinning ratio with your chosen paint:
Mixing

Combine your emulsion paint with water, at the correct ratio, in a bucket. Stir well to achieve a consistent blend.
Applying

Use a roller for even coverage, starting from the top of the wall and working downwards. You may want to use a paintbrush to reach edges or corners.
Drying

Allow the mist coat to dry completely before moving to the next layer. Typically, this takes around 24 hours.

The mist coat creates a base layer that seals the plaster without blocking it from breathing. This step makes it easier for additional coats to adhere properly and ensures even colour across the entire surface.

Application Techniques

Once the mist coat is completely dry, you’re ready to apply additional coats. 

First Coat

The first coat of undiluted paint should be applied evenly with a roller. If the paint seems too thick, thin it in accordance with the manufacturer’s recommendations in the respective data sheet, to enhance flow without creating another mist coat.

Drying Time Between Coats

Allow each coat to dry fully before continuing to paint. Refer to the manufacturer’s instructions for best results.

Second and Final Coats

For the final layers, apply as you would any painted wall, but pay attention to even roller strokes to avoid lap marks or streaks.

Using the right tools, such as quality rollers and angled brushes, helps achieve a smooth and consistent finish when painting over plaster.

Choosing the Right Paint for New Plaster

Using a breathable paint or one specifically formulated for fresh plaster is highly recommended, as these options enable any remaining moisture to escape without compromising the finish. Zanders Cover Coat Vinyl Matt and Zinsser Perma-White Interior are excellent emulsions suited for plastered surfaces. With a vast colour selection, these paints allow new plaster to integrate smoothly with the rest of the room’s décor.

Aftercare and Maintenance for Newly Painted Plaster

The curing process doesn’t end with the final paint layer. After painting on to new plaster, wait at least 1-2 weeks before hanging anything on the walls or washing them to avoid disrupting the paint until it is fully cured.

Conclusion: Get the Perfect Finish on New Plaster Every Time

Learning how to paint new plaster properly ensures a professional result. By following these steps, from mist coating to choosing the right paint, you can avoid the most common mistakes and achieve a finish that will last. Remember, preparation is key, so take your time with each step for the best outcome.

If you have questions about your particular project, leave a comment below, and Rawlins’ Technical Experts would be happy to assist!