What is Primer Paint? Paint Primer 101

paint primer

by Marvin - April 24, 2023

What is Primer Paint?

Primer paint, otherwise known as a base coat or undercoat, is applied before your paint’s topcoat. Its primary purpose is to maximise paint adhesion to the surface and to ensure a long-lasting, smooth finish for many years. For harder surfaces that lack porousness, such as metal, primer is a must for proper bonding and coverage.

Primers with stain-blocking properties are also used to prevent the bleed-through of unsightly stains from surfaces like nicotine, smoke or water stains. If you have a stained wall or ceiling, using this type of primer can help you achieve a better final finish.

What is Primer Made Of?

Most primers are made from a mixture of solvent, resin and additive agents. The type of solvent used will depend on the paint’s intended use, as well as the type of surface being painted. Some primers, for example, contain polyethene, typically used for plastic bags and packaging, providing a more durable finish.

The resin component binds the primer together, while the solvent ensures durability. The additive agent prevents any coating defects and improves the primer’s flow and levelling properties.

What is the Difference Between Primer and Paint?

The primary differences between primer and paint lie in their ingredients and purpose. While primer contains mainly binders, resins and solvents, paint consists of a mixture of pigments, binders and solvents.

A paint’s pigments are responsible for its colour, ensuring it can withstand the elements and other external factors. Pigments are made from either natural or synthetic insoluble particles, which are then combined with a binder to form paint.

In contrast, primer does not contain any pigments as it doesn’t have to be a specific colour. It is applied before the paint and acts as its foundation, whilst improving durability, smoothness and coverage.

What Are the Different Types of Primer?

There are three types of primer: latex, oil-based and shellac primer. Each type has its advantages and disadvantages, so choosing the right one for your project is important.

Latex Primers

Latex primers are the most popular type of primer on the market. They are made from water-based acrylic resins, and are quick-drying, and easy to clean up with just soap and water.

This primer is typically used on unfinished dry walls as they even out previous patch work and repairs on the surface. It’s also commonly applied to brick walls, softwood, galvanised metal fences, and concrete. Overall, latex primers are versatile and can be used on various surfaces.

The biggest drawback of latex primers is that they are not as durable as oil-based primers due to containing fewer additives. And unlike a stain blocking primer, they aren’t as effective at covering stains. For example, an oil-based primer would be a better option if you’re painting severely stained walls.

Advantages of latex-based primer

  • Quick drying times
  • Simple to apply or touch up
  • Easy to clean with just soap and water
  • Non-flammable
  • Often comes in Low VOC or Zero VOC formulas

Disadvantages of latex-based primer

  • Cannot cover dirt
  • More susceptible to peeling and flaking
  • Not as durable or stain-resistant as oil-based primers
  • Sensitive to sudden temperature changes

Oil-based Primers

Oil-based primers contain high amounts of oil and have a thicker texture than latex-based primers. When dried, it has a harder and more durable finish that is resistant to peeling, flaking and chipping. However, due to its rigid nature, oil-based primers are not commonly used on surfaces that require sanding, shaping or other prep work.

The primer type is typically used on wooden, metal, and already painted surfaces. In addition to effectively blocking out stains, they can stop colour bleeding from knots in wood and tannin stains on unfinished or new wood.

Oil-based primers have a few disadvantages as well. First, they generally contain high amounts of VOCs , which can harm you and the environment. They also have a strong odour, are slow to dry and require paint thinners or mineral spirits for cleanup.

Advantages of oil-based primer

  • Known as a “stain-killer”, they effectively block out stains
  • Dries to a hard, durable finish
  • More resistant to chipping, peeling and flaking
  • Can better withstand temperature changes, making it an excellent choice for your exterior paint jobs

Disadvantages of oil-based primer

  • Releases a strong odour
  • Contains moderate to high VOCs
  • It takes a long time to dry
  • Difficult to clean up – requires paint thinners or mineral spirits

Shellac Primer

Shellac primer is made from a resin secreted by the female lac bug – hence its name. It has excellent adhesion properties and is typically used to seal wood, plastic, metal, plastic and old varnish.

Like oil-based primer, they’re excellent at blocking stains and odours. If you have heavily stained surfaces with graffiti, smoke stains and watermarks, this primer type is ideal. They can also be applied to walls with latex and oil-based paint, making it a solid choice for repainting jobs.

Shellac primers are relatively quick to dry as they won’t penetrate the surface as deeply as oil-based primers. However, they’re sensitive to hotter temperatures and are not water-resistant. Because of these reasons, shellac primer is only used by interior painters for smaller surface areas, otherwise known as spot-priming. Shellac primer is also best for cabinet painting and for sealing any wood surfaces.

Advantages of shellac primer

  • Dries quickly
  • Excellent at sealing and blocking stains and odours
  • You can apply it over latex paint and oil-based paint

Disadvantages of shellac primer

  • Sensitive to heat – can start to soften in warmer temperatures
  • Not water resistant, meaning they’re a poor choice for exterior surfaces
  • Only suitable for spot priming and not for large surface areas

When to Use Primer

Is primer required every time you splash a new coat of paint? Not always. In some cases, you can bypass the primer stage and go straight to painting.

However, primer is recommended for many surfaces, such as bare wood, metal, drywall and previously painted brick. Besides enhancing adhesion, it also maximises the colour you see from your chosen paint, making it more vibrant and ‘true to colour’. This  is especially important when going from a dark to light paint, or vice versa.

Use primer in the following scenarios:

Porous surfaces

Any porous surface such as new wood, concrete and drywall easily absorbs moisture, making them susceptible to different types of corrosion. A coat of primer will help seal the surface and provide a better grip for paint to adhere to.

You’re painting a light colour over a dark colour

When your paint’s colour contrasts significantly with the wall’s current colour, you’ll likely need a primer to help ‘hide’ the old paint colour and provide an even base for the new one. By adding primer, you’ll achieve the colour that’s advertised on the tin.

Stained walls

As mentioned, oil-based and shellac primers are excellent at sealing and blocking out stains. If you’re painting over a wall with watermarks, rust, grease or other surface blemishes, a coat of stain-blocking primer will effectively cover them up.

You’re painting over a glossy surface

High-gloss walls aren’t just shiny but also relatively smooth. This makes it difficult for paint to properly ‘grip’ and stick to the surface. A coat of primer and a light scuffing with sandpaper will provide a rougher surface for the paint to grab onto. We recommend using two primer coats for best results.

Metal and plastic

No matter how many coats you try to apply, metal and plastic surfaces aren’t effective at gripping paint. Primers maximise adhesion, ensuring your paint sticks and doesn’t flake off.

Metal comes with its own primer paint known as ‘metal primer, which you should use specifically for this surface type.

So are there any scenarios where primer isn’t needed? The following don’t always require a new coat of primer:

Walls that are in good condition

If your walls are free from surface imperfections, such as smoke marks, grease, and water stains, there’s potentially no need for primer. This is why before any painting job, it’s always a good idea to give your surfaces a quick once-over with a damp cloth and cleaning solution to remove any dirt or debris.

If you’re repainting a surface with the same or similar colour

One of the goals of a primer is to adapt your base colour to the paint you’re using. If your previously painted surfaces are the same or similar colour, then there’s no need to use a primer. Your existing paint will provide the necessary ‘base’ for the new paint.

How Many Coats of Primer Do You Need?

In most cases, applying one or two coats of primer will suffice. However, it will depend on your wall’s colour, material, condition and the primer you’re using.

You’ll only want to you one coat of primer if:

You’re painting on a white wall

Since part of the intention for primer is to help ‘hide’ the wall’s original colour, you won’t need excessive coats if your wall is already white. Once the primer has evenly distributed across the surface, you’re ready to start painting.

Your primer is tinted

If you need to drastically change the colour of your walls, such as light to dark or white to black, then a tinted primer with your preferred paint colour can help to cut down the number of coats you’ll need.

When to use two coats of primer:

You’re painting plaster or drywall that’s unfinished

Raw drywall and plaster surfaces have multiple areas with higher levels of porosity. As a result, they tend to absorb more paint, making it difficult for the paint to adhere and ‘cure’ properly. They also absorb primer at different rates, which can lead to uneven surfaces and blotches.

By applying two primer coats, the first will be absorbed or soaked up by your surface. The second coat covers the first layer, providing a smoother and more even layer. It also covers any blemishes that you didn’t fully resolve with the first coat.

Your surface material is bare wood

Similarly to drywall, an unfinished wood surface is very porous. Even with a single coat of wood primer, it usually isn’t enough to fill in the pores and create an adequate ‘undercoat’ for paint.

You’ll need two coats of primer to thoroughly smooth out the grain, masking any knots that may be present. We also recommend using one that’s oil-based, as it will provide extra protection against any water damage that may occur. Latex-based primer can cause your wood to swell, which can result in cracks and chips.

You’re painting a dark wall with a lighter hue

As mentioned, to cover a darker colour with a light paint, you’ll need first to use a primer. This prevents its original colour from seeping through and affecting the paint job. We recommend applying two coats of white primer to help hide the dark colour and provide an even ‘base’ for your paint.

How to Apply Primer

Primer doesn’t require any special application techniques and can be applied using the same equipment you would use for paint. This includes a brush, roller, or paint sprayer. However, you must keep a few things in mind to ensure proper application.

1. Use the right type of primer: As we mentioned, there are different types of primer available, each with its own specific uses. Be sure to consider stain blocking primers for heavily stained walls and latex-based primers for walls in good condition.

2. Prepare your surface: If your wall has cracks, lumps or is simply full of grime, you’ll need to handle these before applying primer. Clean your walls using a detergent and water solution and repair any wall damage with your spackling compound.

3. Pick the right brush: Latex primers work best with synthetic brushes, and oil-based primers work best with natural-bristle brushes.

4. Cover your floor and furniture: Like with paint, you’ll want to protect your furnishings and flooring from primer drips and spills. Cover them with a drop cloth or plastic sheeting before beginning.

5. Cut in the edges: Begin by ‘cutting in’ your wall’s edges with a brush, which means painting around your surface’s perimeter and corners. You can then use a roller for the larger, flat surfaces. We also recommend painting in smaller sections.

6. Let it dry: Be sure to give your primer plenty of time to dry before painting over it. Since all primer types have different drying times, always read the manufacturer’s instructions to see how long yours will take.

7. Apply paint: Once your primer is dry, you can go ahead with your paint job! Don’t be afraid to add an extra coat or two of paint if needed.

How Long Does Primer Need to Dry?

We’ve just mentioned that primer drying times will depend on the type you’re using. In general, however, most primers take about 30 minutes to an hour to dry. If you’re ready to apply your paint, you’ll have to wait a little longer. Primers can take up to 3 hours to dry, so be patient!

You can usually tell if your primer is dry by gently pressing your fingers against the wall. If your primer feels tacky or some come off on your fingers, it’s not ready yet. It should be good to go if it feels dry and smooth to the touch.

Can You Use an Exterior Primer Indoors?

No, we don’t recommend using an exterior primer indoors. These products are designed to withstand bad weather conditions and aren’t necessary for interior walls or other surfaces.

While interior primers only intend to seal the surface and create a uniform appearance, exterior painting primers are made to protect against mould, mildew and other damage that the elements can cause. This means they often contain toxic chemicals, such as VOCs, that you don’t want to be exposed to indoors.

What about Self-Priming Paint?

Self-priming paint is a newer innovation that provides the best of both worlds – the convenience of primer and paint in one can.

This paint type has a thicker consistency than regular paint, resulting in a thicker paint layer. While convenient at first glance, its main drawback is that it can be more costly than using primer and paint separately. Furthermore, it doesn’t excel in either task the way that primer or paint can on their own.

The bottom line: while self-priming paint is a seemingly a good product, the verdict is still out on its true effectiveness. As such, we still recommend using primer and paint separately for the best results.

Let Sidepost’s Professional Painters Help!

Now that you know all there is to know about primer, it’s time to get started on your project! However, if you’d instead leave it to the professionals, that’s where we come in.

At Sidepost, our experienced team of painters can help you with every step of your home improvement project – from choosing the suitable primer to painting your walls or other surfaces. We’ll even take care of the cleanup after we’ve accomplished a quality paint job!

To get started, book online or contact us at 1300 138 499 today. We can’t wait to help transform your home!

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