For Livermore area homes and businesses, plastering and painting your walls can breathe life into your space if your interiors look and feel a bit lackluster.  You can paint over a newly plastered wall as long as the plaster has dried and cured completely. Painting protects the plaster, improves its appearance, and adds to the space’s overall aesthetics once the plaster has dried and hardened. However, adequate preparation and paint selection are crucial to guarantee adhesion, longevity, and a high-quality finish. 

Understanding the proper timing and technique for painting over plaster is essential for the following reasons: proper adhesion, surface preparation, low moisture content, priming, choosing the right paint, and paint application techniques.

Understanding plaster walls

Plaster is a building material that can be used to mold and cast decorative features as well as to coat walls and ceilings decoratively and protectively. The process involves heating minerals such as gypsum, limestone, or other materials to eliminate water, resulting in a powder that may be molded and shaped when combined with water. After drying, it creates a sturdy and long-lasting surface. 

Plaster comes in popular varieties that are used for walls, each with unique qualities and uses:

• Gypsum plaster – Gypsum plaster is often used for interior walls and ceilings. It is mostly made of gypsum, doesn’t require lime, and has a smooth finish. Gypsum plaster is a common material for modern buildings since it sets quickly and is fire-resistant.
• Lime plaster – One of the earliest kinds of plaster is lime plaster, made of lime combined with water and sand. It is perfect for sustainable building projects and historic restorations as it is pliable, breathable, and has inherent antibacterial qualities. Compared to gypsum plaster, lime plaster requires more time to set.
• Cement plaster – Because of its durability and resistance to moisture, cement plaster—a mixture of Portland cement, sand, and water—is used for exterior walls and damp spaces like bathrooms and kitchens. It can be put over concrete, stone, or brick surfaces and is also utilized for its robust structural qualities.
• Clay plaster – Composed of clay, sand, straw, or other fibers, clay plaster is environmentally friendly and offers excellent moisture regulation, making it suitable for natural buildings. It’s known for its ability to “breathe,” which helps to maintain indoor air quality.
• Venetian plaster – Made from lime and combined with marble dust, Venetian plaster is an aesthetically pleasing finishing plaster that mimics stone or marble. It is applied thinly in several coats and polished to a high gloss. This plaster adds a distinct depth of color and texture to ornamental treatments on walls and ceilings.

The drying and curing process of new plaster

Allowing the new plaster to dry and harden is crucial to achieving a durable surface suitable for painting or wallpapering. Of course its important to have any old wallpaper removed before plastering.  The process involves both the physical evaporation of water from the plaster and the chemical reactions that cause it to harden. Here is a detailed overview:

1. Drying phase

• Initial setting – After the plaster is applied to the walls or ceiling, it begins to harden. In this case, the plaster begins to harden but is still quite wet. The time required for the plaster to harden can vary depending on the type of plaster used, the thickness of the application, and the environmental conditions.
• Evaporation – The water in the gypsum mixture begins to evaporate, leaving solids behind. Adequate ventilation is crucial at this stage to allow moisture to escape and speed up the drying process. However, excessive airflow can cause the plaster to dry too quickly, which leads to cracks.
• Environmental factors – Temperature and humidity significantly affect drying time. Plaster dries best in warm, moderately humid conditions. A cold or excessively moist environment slows down drying, while hot and dry conditions can cause the plaster to dry too quickly and crack.

2. Curing phase

• Chemical reaction – Curing is a chemical process that continues after initial drying. During hardening, a chemical reaction (hydration) takes place in the plaster, which strengthens the bond between the plaster particles and makes the surface hard and durable.
• Timeframe – The healing process can take much longer than the initial drying. Although the cast may feel dry to the touch within a few days, healing may take several weeks. The exact time depends on the type of plastering and environmental conditions.
• Importance of curing – Proper curing is essential to achieve full strength and durability of plaster. Premature painting or wallpapering can trap moisture and cause problems such as mold, peeling, or bubbling.

Environmental factors like temperature and humidity greatly affect the drying time of the plaster. Here is a general overview of the role of these factors:

• Temperature – Warm temperatures can accelerate drying because heat energy increases the rate at which water evaporates from the plaster. Warm air holds more moisture than cold air, which speeds up drying in hot conditions. On the other hand, cold temperatures slow down evaporation and increase the drying time of the plaster. However, hot conditions can cause the plaster to dry too quickly, leading to cracking and loss of strength.
• Humidity – Humidity also can play a significant role in plaster drying time. High humidity slows the drying of the plaster because moist air takes longer to absorb water from the plaster. If the air is saturated with moisture, the water in the plaster does not evaporate as quickly, which increases the drying time. On the other hand, in conditions of low humidity, the air can absorb moisture more easily, so the plaster dries faster.

Risks of painting too soon

What happens if you paint on plaster that has yet to dry and harden properly? Applying paint too soon can lead to several serious problems:

• Paint delamination – It is one of the most common problems when painting over wet plaster. Delamination refers to paint separating or coming off the plaster surface. It is because the moisture in the plaster prevents the paint from adhering properly. As the mortar dries and shrinks, the bond between the paint and the mortar weakens, causing the paint to peel or flake.
• Cracking – Wet plaster shrinks as it dries. If a coat of paint has already been applied, shrinkage of the mortar can cause the paint to crack and crack. Not only do these cracks damage the appearance of the walls, but they can also expose the plaster to additional moisture problems, making the problem worse over time.
• Mold growth – Drywall that stays wet for a long time creates an ideal environment for mold and mildew growth. When paint is applied to wet plaster, it can trap moisture and create conditions that encourage mold growth beneath the paint surface. It may lead to health problems for residents and damage to the wall structure. Mold growth under paint can appear as discoloration and seriously degrade indoor air quality.
• Adhesion issues – Besides shaking, moisture from wet plastering can prevent the paint from properly adhering, resulting in poor paint and wall adhesion. It can result in an uneven or patchy surface where some areas may appear well-coated while others appear thinly coated or bubbled.
• Efflorescence – Moisture penetrating the plaster can carry salts to the surface. If painted prematurely, these salts can cause efflorescence, causing crystalline precipitates to form on the paint surface. It not only looks ugly, but it can also cause the paint to stick to the plaster surface.
• Color and finish problems – Moisture in the plaster can affect the paint’s color and finish. As the mortar dries, it can cause the paint to dry unevenly, resulting in streaks or spots. Glossy colors may appear dull in some areas, while matte surfaces may need to be more uniformly smooth.

Uneven paint finishes and color inconsistencies

Uneven paint surfaces and color inconsistencies can significantly weaken the appearance of a painted surface, affecting both its aesthetic appearance and perceived quality. Here are some of the more common aesthetic problems that can occur and their causes:

 1. Uneven paint finishes

• Brush marks and roller strokes – Visible application strokes can cause an unprofessional appearance. This problem is often caused by using poor-quality tools, applying too much or too little paint, or failing to maintain a wet edge during application.
• Runs and sags – Paint drips or slops create uneven surfaces and reduce surface smoothness. They are usually caused by applying too much paint in one coat or painting on a vertical surface without proper technique.
• “Orange peel” texture – This describes a surface that resembles an orange peel with a slightly rough texture. It is common in spray painting and can be caused by several factors, such as spraying the paint too thick, using viscous paint, or spraying at the wrong distance from the surface.
• Lap marks – These are noticeable differences in the appearance of paint due to overlapping of the edges of partially dried paint. Circular marks occur when the painter does not hold the wet edge, causing the wet and already dry paint to overlap.

2. Color inconsistencies

• Fading and chalking – Paint can fade over time or begin to chalk due to exposure to sunlight and weather elements, leading to uneven coloration across the surface. The quality of the paint and the pigments used can influence how quickly this occurs.
• Mismatched colors – Even slight variations in paint color can be noticeable and detract from the uniformity of the painted surface. This can happen when mixing paint from different batches or failing to mix paint before application.
• Bleeding – Older colors or stains bleeding through the new paint layer can cause color inconsistencies. Inadequate or lack of surface preparation or failure to use a primer when needed is the cause of bleeding.
• Patchiness – Paint’s uneven absorption, especially on porous surfaces, can result in a patchy appearance. It is often resolved with proper surface preparation and the application of a suitable primer.

Preparing to paint

Here is a step-by-step guide to help ensure your plaster is fully dry and ready for painting:

1. Allow sufficient drying time.

• New plastering – Usually takes at least four weeks to dry completely. It can vary depending on environmental conditions such as humidity and temperature.
• Spot repair – Small repairs can dry more quickly, often in days or weeks, depending on the depth of the site and environmental conditions.

1. Inspect the color – plaster changes color as it dries, usually starting to darken and lighten. A uniform light surface color is a good first indicator of plaster drying.

2. Check for dampness

• Touch test – Gently press your hand against the plaster. It should feel dry and at room temperature. If it feels cool or wet, it needs more time.
• Moisture meter – Use a moisture meter specially designed for plastering for more accurate measurements. This tool gives the final moisture content and helps you decide if the plaster is dry enough. The acceptable moisture content depends on the meter and the scale, but it should be close to the outdoor humidity level of dry interior walls.

1. Assess environmental conditions – High humidity and low temperatures slow drying. Use a dehumidifier to reduce humidity, and, if possible, raise the room temperature slightly to facilitate drying.
2. Allow sufficient ventilation – Ensure the room is well-ventilated to allow moisture to escape. Open windows or use fans to circulate air, but avoid direct airflow on the plaster, which can cause uneven drying.
3. Inspect for cracks or damage – Before painting, inspect the plaster for cracks, damage, or unevenness. Touch up these areas as needed and let the ends dry completely.
4. Prime – When the plaster has completely dried, it is recommended to apply a suitable primer for the plaster. It helps seal the plaster, create a good base for the paint, and ensure even coverage and color.
5. Do patch test painting – If you are uncertain about dryness, you can do a spot test by applying the paint to a small area. After drying, inspect the test area for moisture damage or adhesion problems.

The importance of a well-ventilated space

The importance of a well-ventilated space for drying plaster cannot be overstated, as it directly impacts the quality, durability, and safety of the plastering work. Here are several reasons why ventilation is crucial:

• Moisture control – The log must dry evenly and gradually to prevent cracking. A well-ventilated area ensures excess moisture escapes, reducing the risk of structural weaknesses if the plaster dries too quickly or unevenly.
• Mold and mildew prevention – Adequate ventilation helps prevent moisture that can cause mold and mildew. It can damage the plaster and cause health risks for residents.
• Strength and durability – Proper drying increases the strength and durability of plaster. Without good ventilation, plaster can remain wet inside even when the surface appears dry, causing long-term problems such as crumbling or non-adhesion of surfaces.
• Air quality – Volatile organic compounds (VOCs) and other chemicals can be released into the air during drying. Good ventilation ensures their spread, maintains better air quality, and reduces potential health risks for people in the vicinity.
• Efficiency and cost-effectiveness – Well-ventilated spaces can reduce the time it takes for plaster to dry, making the construction or repair process more efficient. It can lead to cost savings and less disruption to the site.

Tips for speeding up the drying process

If necessary, speeding up the drying process of various items or substances safely involves techniques that minimize risk while effectively reducing moisture. Here are some general tips for different scenarios:

• Use direct sunlight to speed drying, but be careful with items that may fade or deteriorate from UV exposure.
• Use absorbent materials such as towels, sponges, or proprietary products.
• For indoors, reducing total humidity with dehumidifiers can speed up the drying time of many items.
• Set a fan to blow air over the surface to increase evaporation, but avoid high speeds as it can cause dust to stick to the surface.
• Apply thin layers of paint. Several thin layers dry faster than one thick layer.
• Use a dehumidifier in the room to reduce humidity and speed drying.
• Safely increase the room temperature, if possible, as heat accelerates drying.

Primer: your best friend

Using a primer on new plaster walls is crucial for several reasons:

• It seals the surface.
• It improves the adhesion of the topcoat.
• It provides the paint finish with a uniform appearance
• It hides stains.
• It enhances paint performance and durability.
• It provides a barrier against moisture.

When preparing plaster walls for painting or wallpapering, choosing the right type of primer is essential for a durable and visually pleasing finish. You also have to consider important factors such as the condition of the walls, the type of paint you plan to use, and any specific issues like stains or odors you need to address. 

Here are some types of primers suitable for plaster walls, along with their benefits:

• PVA (polyvinyl acetate) primer – It is specifically designed for sealing plaster walls. It prevents the plaster from absorbing too much paint, leading to a more uniform finish. PVA primer also helps in adhering the paint to the surface, reducing the amount of paint needed and ensuring that the finish lasts longer
• Oil-based primer – It is excellent for sealing and protecting plaster walls, especially if the walls are old and have never been painted. They are particularly good at blocking stains and preventing bleeding from the underlying material. Oil-based primers also adhere well to the surface, providing a solid base for any paint.
• Shellac-based primer – It offers superior stain-blocking capabilities, making it ideal for plaster walls that have been exposed to smoke, water, or other types of stains. Shellac-based primers dry quickly and create a hard surface that is excellent for painting. This type of primer is also good for sealing odors.
• Latex primer – It is water-based and less odorous than oil-based primers, making it more user-friendly and easier to clean up. Latex primers offer good adhesion to plaster surfaces and are flexible, which helps prevent cracking. They are also good for sealing porous surfaces and providing a smooth base for paint.
• Acrylic primer – It is another water-based option that provides excellent adhesion and durability. Acrylic primers are suitable for new or previously painted plaster walls and work well under various paint types. They are less likely to yellow over time and can resist moisture.
• Stain-blocking primer – A stain-blocking primer is ideal for plastered walls with problematic stains or discoloration. It is designed to prevent stains from bleeding through the final paint coat, ensuring a clean and uniform appearance. Stain-blocking primers may be oil-based or water-based, depending on the specific formulation.

Applying primer to plaster walls before painting is an essential step to ensure a smooth, durable finish. Here’s a step-by-step guide on how to apply primer correctly:

1. Prepare the walls

• Clean the walls – Remove any dust, dirt, or grease from the walls. You can use a damp cloth or sponge and a mild detergent if necessary. Let the walls dry completely.
• Repair damages – Fill any holes or cracks with plaster or a suitable filler. Once dry, sand the repaired areas until smooth.
• Sand the walls – Lightly sand the entire wall surface with fine-grit sandpaper to ensure the primer adheres well. This step is especially important if the plaster is glossy or has been painted previously.
• Remove dust – After sanding, remove all dust with a clean, damp cloth or tack cloth.

2. Apply primer

• Choose the right primer –Use a primer suitable for plaster walls. If your walls are new and have never been painted, a plaster sealer or a primer sealer is recommended to prevent the plaster from absorbing too much paint.
• Tape off areas – Use painter’s tape to protect areas you don’t want to be primed or painted, like trim, windows, and doors.
• Cut in – Begin by “cutting in” the primer around the edges of the wall with a paintbrush. It means painting a 2- to 3-inch strip along the edges, corners, and areas where a roller cannot reach.
• Use a roller for large areas – For the main surface of the wall, use a roller. Dip the roller into the primer, removing any excess to avoid drips. Apply the primer using slightly overlapping strokes, starting from the top of the wall and working your way down.
• Apply evenly – Ensure an even application of primer across the wall. Avoid applying too much primer in one area and not enough in another.
• Let it dry – Allow the primer to dry completely. Check the primer’s label instructions for drying times, as it can vary depending on the brand and type.

3. Inspect and apply a second coat if necessary

• Inspect the coverage – Once the primer is dry, check for any uneven areas or spots where the plaster shows through. 
• Apply a second coat if needed – If coverage is uneven or insufficient, apply a second coat of primer, following the same steps as before.

Choosing the correct paints and tools

Here’s a rundown of the best types of paint for plaster walls, focusing on breathability and overall performance:

• Lime-based paints – They are very breathable and naturally antibacterial, making them an excellent choice for historic and new plaster walls. They work well with the natural properties of plaster, allowing moisture to evaporate from the surface, which is particularly beneficial in older homes where moisture issues are more prevalent.
• Clay paints – Clay paints give off a unique aesthetic with a very matte, natural finish and excellent eco-friendly credentials. They are highly breathable and can help regulate indoor humidity levels, absorbing excess moisture when the air is damp and releasing it when the air is dry. This makes them ideal for plaster walls, contributing to a healthier indoor environment.
• Silicate (mineral) paints – Silicate paints penetrate the surface of the plaster and chemically bond with it, creating a durable, long-lasting, and highly breathable coat. They are resistant to UV light, meaning they won’t fade over time, and they’re also mold and algae-resistant. These paints are well-suited for both interior and exterior plaster walls.
• Acrylic emulsion paints – While not as breathable as lime, clay, or silicate paints, high-quality acrylic emulsion paints can be suitable for plaster walls if breathability is not a big issue. They offer a wide range of finishes and colors, are easy to apply, and dry quickly. Some modern acrylic paints are formulated to be more permeable, so look for those options if moisture is a concern.
• Distemper paint – Distemper is a traditional paint made from water, chalk, and pigment, sometimes with a binding agent like lime. It’s very breathable and has a soft, velvety finish. However, distemper paint is not as durable as modern paints and can mark easily, so it’s best for low-traffic areas and ceilings.

Having the right tools and equipment is crucial to achieve a smooth application in your painting projects. Here’s a list of recommended items for house painting:

• Paint rollers and covers
• High-quality brushes
• Painter’s tape
• Sandpaper or sanding blocks
• Paint tray and liners
• Extension pole for paint roller
• Drop cloths
• Ladder

Painting new plastered walls: step-by-step guide

After ensuring the plaster has dried and having primed the newly plastered walls, it’s time to paint them! Here’s a step-by-step guide to help you through the process:

1. Applying the top coats:

• Paint choice – Use a water-based emulsion for the final coats. You may need two or more coats to achieve the desired opacity and finish.
• Application technique – Apply each coat with a roller in a uniform direction, using a brush for edges and corners. Allow each coat to dry before applying the next. Drying times can vary based on paint type and environmental conditions.

2. Finishing touches 

Check the walls for any missed spots or uneven areas after the final coat has dried. Then, use a small brush for any necessary touch-ups.

Bonus tips:

• Keep the room well-ventilated during the painting process to aid in drying and reduce paint fumes.
• Good lighting is essential to spot any painting imperfections.

Following these steps should help you achieve a professional-looking finish on your newly plastered walls. Take your time with each step to ensure the best possible outcome.

Aftercare and maintenance

Maintenance of freshly painted plaster walls in Plis essential to maintain the appearance and longevity of the paint. Here are some tips to help you take care of your newly painted plaster walls:

• Allow adequate drying time – Fresh plaster paint needs time to cure completely. It usually takes about 2-4 weeks for the paint to cure, but this can vary depending on the type of paint used and environmental conditions. Avoid touching or washing the walls during this time to avoid damage.
• Avoid humidity – High humidity can prevent paint from drying and curing. Try to keep the room well-ventilated and maintain a moderate temperature for the paint to cure properly.
• Clean gently – Once the paint has set completely, you can clean the walls as needed. Gently wipe off any dust or dirt with a soft, damp cloth. Avoid using harsh chemicals or abrasive cleaners, as they can damage the paint.
• Address leaks immediately – If something spills on the wall, clean it up as soon as possible to avoid stains. Gently wipe the spilled area with a damp cloth without rubbing, which could smear the spill or damage the paint.
• Repair as needed – If you notice any cracks or scratches, repair them with paint residue to keep the walls looking fresh. Use a small brush for precision and try to blend with the surrounding wall of the repaired area.
• Protect from furniture and sunlight – Keep furniture and other items a short distance away from walls to prevent scratches and scrapes. Additionally, prolonged exposure to direct sunlight can cause painted surfaces to fade over time, so consider window coverings to protect your walls from UV damage.
• Use the correct color when repainting – If you decide to repaint your walls in the future, use a color that matches the existing type. The best result is ensured if the surface is properly prepared before applying the new paint.
• Dust regularly – Regular cleaning can prevent the build-up of dust, which can stick more firmly to the wall over time. Use a soft, dry cloth or dust brush to remove surface dust.

Common issues to watch out for in the first few months after painting

When painting newly plastered walls in Mountain House, you must address several common problems in the first few months. These can affect the appearance and durability of the paint if handled incorrectly:

• Drying and curing time – Plaster must be completely dry before painting, which can take several weeks, depending on thickness and environmental conditions. Painting over wet plaster can cause discoloration, flaking, or blistering.
• Efflorescence – This is a condition where salt deposits form on the surface of plaster as it dries, resulting in a white powdery residue. If painted over, it can cause the paint to peel. Removing efflorescence before painting is crucial.
• Cracking and shrinkage – As new plaster dries, it can shrink and crack. Before painting, it must be filled and smoothed so that the surface is smooth and uniform.
• Poor adhesion – Paint may not adhere well to smooth and unprimed plaster. Using a primer designed for newly plastered walls can improve paint adhesion and create a more durable surface.
• Moisture damage – If the plaster remains wet or the environment has high humidity, the paint can bubble or peel. These problems can be prevented by proper ventilation and making sure the plaster is completely dry.
• Uneven absorption – Different absorption rates between patched areas and the original mash can cause uneven results. As the first layer, a mist coat (a water-based paint layer) helps to even out the absorption rates across the wall.
• Mold and mildew – Mold and mildew can form on painted plaster walls in high-humidity areas such as bathrooms or kitchens. Using mold-resistant paint or adding a mold inhibitor to the paint can help prevent this.
• Color inconsistencies – Inconsistencies in plaster drying or texture changes can cause significant color differences after painting. Applying additional paint or a high-quality primer will help achieve an even color.

Proper preparation of the plaster walls before painting is the key to avoiding these issues. It includes ensuring the plaster is fully dry, applying a suitable primer, using the correct type of paint, and addressing any surface imperfections. Regular checks in the months following painting can also help catch and rectify any emerging problems early.

When to call a professional

Hiring a professional paint contractor to paint freshly plastered walls can be beneficial in several scenarios, ensuring optimal results and avoiding potential problems. Here are some situations where hiring a professional might be a better option:

• High-quality finish
• Ability to deal with complex surfaces or designs on walls
• Speed and efficiency
• Knowledge of materials
• Ability to deal with problematic walls (such as bumps from an improperly plastered surface)
• Safety
• Warranty and Insurance
• Stress reduction
• Value for money

In these scenarios, the benefits of hiring a professional painter outweigh the cost, ensuring a stress-free process with excellent results.

How to choose a reputable painting contractor

Choosing a Tracy area professional painting contractor is critical to ensuring quality work and a satisfactory outcome for your painting project. Here are some steps to choose the right painting contractor:

• Research and get references – Ask friends, family, neighbors, or colleagues for recommendations. You can also search online for painting contractors in your area and read reviews on platforms like Google, Yelp, or Angi (formerly Angie’s List).
• Check credentials – Find painting contractors who are licensed, bonded, and insured. These credentials ensure that the contractor is legitimate and able to compensate for any damages or injuries incurred during the project.
• Check for experience and knowledge – Consider the experience and knowledge of the painting contractor. How long have they been in business? Do they specialize in residential or commercial painting? Look for contractors who have experience with similar projects.
• Check portfolio and references – Ask the painting contractor for a portfolio of their previous work. It will give you an idea of the quality of their work and the type of projects. Additionally, ask for references from previous clients, contact them, and ask about their experience working with the contractor.
• Get multiple quotes – Get quotes from at least three different painting contractors. Make sure quotes are detailed and include labor, material, paint, and other costs. Compare quotes to find out which contractor offers the best value for your money.
• Inquire about process and materials: Ask about the painting process and materials the contractor plans to use on your project. A professional contractor should be able to explain their process in detail and recommend quality paints and materials that will provide long-lasting results.
• Consider communication and professionalism – During the initial inquiry process, pay attention to the contractor’s communication and professionalism. A trustworthy contractor should answer your questions, provide clear and detailed information, and be punctual with appointments.
• Make sure to get contracts and warranties – Once you’ve chosen a painting contractor, be sure to get a written contract that defines the scope of work, project timeline, payment schedule, and any warranties offered. Before signing, read the contract carefully and explain any terms you do not understand.
• Trust your instincts – Trust your instincts when choosing a painting contractor. If something doesn’t feel right or you have doubts about a particular contractor, it’s best to keep looking until you find a contractor you feel comfortable and confident with.

Conclusion

To paint or not to paint newly plastered walls? The answer is yes – you can paint them. However, painting plaster is a process that requires a little patience and attention to detail. The key is to allow the new plaster on the wall sufficient drying and curing time before painting over it. If you don’t correctly approach this job, you might end up with a less satisfactory finish.

Painting freshly applied plaster on walls in San Ramon area homes and businesses takes more time and care. Rushing the paint process can lead to multiple problems, which you might end up repeating anyway.  

Do you need any more advice regarding painting on fresh plaster or any other tips for house painting in Livermorel, CA? Contact the Custom Painting, Inc., team today. To discover our range of services or request a free estimate, call us at 925-294-8062 or contact us here.