Primers are paint products that prepare surfaces so that you can then apply paint. When you apply it before painting, it preps the surface for the finish coat of paint, ensuring better adhesion, durability, and overall appearance. In this guide, I will go over the ins and outs of paint primer and why you should be using it for your next DIY painting project.
When To Use Primer
Using a primer can work for some projects, but it’s not always necessary. Knowing when to prime can save you time and money, so here are some situations where you should definitely use a primer to get the best results.
- Unfinished surfaces: Prime unfinished surfaces, including wood, drywall, metal, and concrete, before painting. While it might be tempting to skip this step, if you do, paint may peel, crack, and chalk.
- Different paint types: If you switch between oil-based and latex paint, plan to prime. Many modern primers allow for this transition, but proper surface preparation is still necessary. When painting over interior oil-based woodwork with latex, it’s important to sand or degloss the surface first, then apply a bonding primer before the latex topcoat.
- Covering stains/odors: Primers can block stains and prevent them from bleeding through the new paint. They’re also effective at sealing in odors from smoke or other sources.
- Dramatic color changes: When making a significant color change, especially going from dark to light, primer can help achieve better coverage with fewer coats of paint.
Types of Primers
There are three main types of primers, each with its own strengths and ideal applications. Understanding these differences will help you choose the best primer for your specific project.
Oil-Based Primers
Oil-based primers are known for their excellent adhesion and stain-blocking properties. They’re ideal for unfinished wood, previously varnished wood, woods prone to tannin bleeding (like redwood and cedar), heavily weathered wood, and surfaces with existing paint that’s failing due to chalking or cracking
These primers create a very smooth finish and do an excellent job of filling pores in bare wood without raising the grain. They have a strong odor, though, and release volatile organic compounds (VOCs), and require mineral spirits for cleanup and thinning.
Latex Primers
Latex primers have come a long way in recent years and are now available in low and no-VOC formulas. They’re fast-drying, water-soluble, have a flexible finish that resists cracking, and allow water vapor to pass through, which reduces the likelihood of peeling.
These types of primers work best for unfinished drywall, bare softwoods like pine, masonry (such as brick or concrete block), and galvanized metal (after you properly clean it)
Shellac-Based Primers
Shellac-based primers are fast-drying and use denatured alcohol for thinning and cleanup. While they can be smelly and difficult to use, they excel at blocking water smoke, and rust stains. Since they dry so quickly, you can use them on materials like wood, plaster, metal, and plastic when you need to speed up your project.
Choosing the Right Primer
Selecting the proper primer for a project depends on several factors. Start by looking at your surface material. Different surfaces require different primers. For example, bare wood might benefit from an oil-based primer, while new drywall typically needs a latex primer.
For exterior projects, consider the climate and weather conditions. Some primers are better suited for humid environments, while others perform well in extreme temperatures. Don’t forget to think about the specific needs of the project. Is stain-blocking a priority? Does the surface need extra adhesion?
Whatever primer you choose, make sure it’s compatible with the intended topcoat. While many modern primers work with both oil-based and latex paints, it’s always best to check the manufacturer’s recommendations.
Application and Clean-Up
In my experience, it is best to apply all primers to clean, dry, grease-free surfaces. It’s a good idea to lightly sand surfaces — followed by wiping off any dust with a tack rag or damp cloth — before applying primer so that it binds properly.
Apply primer using a brush, roller, or sprayer, depending on the surface and project size. For best results, follow the manufacturer’s instructions for application methods and drying times. Some surfaces might require more layers, while you can sufficiently cover others with a single coat.
If the primer leaves the surface rough, lightly sand and dust it again before applying the finish coat. This ensures a smooth surface for the paint to adhere to. Failing to sand might result in visible imperfections in the final paint layer.
Clean-up methods vary depending on the type of primer you choose. For latex primers, clean tools with soap and water. Oil-based primers require mineral spirits or paint thinners. Shellac-based primers need denatured alcohol for cleanup.
When it comes to safety, you should always ventilate while using a primer. If opening windows and using fans isn’t enough, wear a mask or respirator. Consider using low or non-VOC latex formulations when painting indoors to minimize any health risks associated with prolonged exposure to strong chemicals.
Tinting Primer
Tinting primer can be a useful technique, especially when making dramatic color changes. Tinting primer to match the paint color improves its hiding ability and smooths the transition between primer and topcoat. This can reduce the number of paint coats needed, saving time and money. It also creates a more uniform base that can enhance the vibrancy of the final color.
Most paint stores can tint primer for you. If doing it yourself, use universal tinting colors and follow the manufacturer’s instructions carefully to avoid over-tinting. Over-tinting can impact the primer’s effectiveness and may alter drying times or the uniformity of the final color.
Tinting is most helpful when making a significant color change, using deep or vibrant colors, or covering dark or stained surfaces. Mismatched or poorly tinted primers can result in inconsistent color and require additional coats of paint.
Tips for Using Paint Primer
Follow this advice for the best results possible when using primer.
Use Specialized Primers
You can use high-build primers to smooth out uneven surfaces, but rust-inhibiting primers offer added protection for metal substrates. Using mold-resistant primers in moisture-heavy environments and surfaces is best for longevity.
Choose Different Tools
Brushes are ideal for small, detailed areas, while rollers provide better coverage for large, flat surfaces. For large projects, consider using sprayers for an even application.
Spot Primer
In some cases, you only need primer on certain sections of a surface rather than the entire area. This is known as spot priming. It can be particularly useful when dealing with repaired sections, spots with visible stains, or areas previously exposed to harsh conditions.
Temperature and Humidity
Environmental factors like temperature and humidity can influence primer application and drying times. Ideally, you should only apply primer in moderate weather conditions. Cold temperatures can make it take longer for the primer to dry and affect how well it sticks. Too much heat can make the primer dry too quickly and make the surface weaker.
Humidity, on the other hand, can prolong the drying process and lead to a tacky surface unsuitable for painting. Understanding and compensating for these factors can be crucial for a successful application.
Product Combinations
Correctly pairing primer and paint can improve the overall performance of the coating. While many primers claim versatility with various paints, matching brands can sometimes offer the best results. Examine the manufacturer’s suggestions and product descriptions to ensure compatibility for optimal adhesion and finish quality.
Apply the Right Amount
Applying too much primer can lead to drips and an uneven surface, while too little may not provide adequate coverage. Follow the manufacturer’s recommendations for application thickness. Ensure you spread the primer evenly, covering all necessary areas without pooling in corners or crevices.
Allow Enough Drying Time
Painting over primer that isn’t fully dry can cause the paint to peel or bubble. Always allow the recommended drying time before applying paint. In humid conditions or with certain primer types, allow extra drying time.
