sealer vs primer

Sealer vs. Primer – Which One Is Better?

Painting may seem like an easy enough job – choose a color, buy a can, and start painting right away. Of course, we must add a few steps before and after to ensure you get the optimal result out of your hard work. 

Everybody knows that primers and sealers are essential for paint jobs, but do we really know what they do? When it comes to sealer vs. primer, which one does the job better? They each have different jobs to perform and if you are a little confused about them, trust me, you are not alone. 

We have got your back! Read further to find out which prep coat would work the best for you. 

What Are Primers and Sealers? 

Both primers are sealers are prep coats, which is a must for all paint jobs. They must be applied to the surface you are working on before you begin painting so that they can stick better and last for a long time. 


Primers mean ‘first,’ and just like their name suggests, they need to be the first to be applied on your substrate.

As an anchor for the paint, they are, in fact, the most important layer for your substrate. The application of a primer will determine the result of your paint job.


Sealers can be substituted as a primer or even be applied before it. Just like you would expect, the liquid coat seals the substrate layer and prevents the added paint or varnish from being absorbed. This protects the layer from being damaged after repeated application over the years. 

Sealer vs. Primer – Which Is Better? 

Now that you know what they are, it is time to figure out which is better. Both words are loosely used when describing prep coats, but there are a few other differences in them. 

Adhesive Properties

The basic job requirement of primers is to provide the best adhesion to a substrate, and the consequent layers added. So, the paint will stick better and uniformly without being patchy. 

And while sealers can perform this function just as well, they are mainly intended to block off any surface porosity.

Concretes and plasters often have an uneven texture, and sealers help fill in the gaps to create a uniform layer for the paint to coat. They can completely transform the quality of your painted surface. 

Binding Properties 

As we mentioned earlier, sealers have excellent binding properties. Traditionally, they were used to correct gypsum plasters.

They are perfect for reconditioning and prepping old surfaces for painting that would have otherwise been impossible to do. If your substrates have an old coat of paint, sealers help increase their compatibility with other paint types. 

On the other hand, primer works as a binder for the paint but not for substrates themselves. So, if you try using them on concrete walls or timbers, you must ensure they are fit for painting and will not develop a crumbly texture. 

Waterproof and Water-Resistance

Most acrylic paints are water-resistant to a certain level but are not completely waterproof.

So, when exposed to rainfall and moisture, your walls may become home to bacteria and mold. And if you live in a humid climate, not waterproofing your walls may be your worst nightmare. 

Seal off unpainted and bare walls with a sealer before you proceed. They will also help wipe out any water stains from leaching through. However, it would be best if you remembered to eliminate other causes as sealers are not 100% foolproof. 

Primers can block off stains too. They can also inhibit paint from sinking to the substrate to some extent as well.

However, primers can trap moisture and is not as water-resistant as sealers. With a higher pigmentation, their sealing properties can increase but at the expense of drying into a roughened surface. 


Prepping your substrates is a strenuous task, but you cannot skip it. You need to scrape off old, chipped paints and sand them down to be as smooth as possible.

To get the best outcome, sand them before, in the middle, and after priming. Some painters even sand while layering their paints too!

In automotive care, sealers are applied post priming to protect the following layers from where you might have sanded through.

But most sealers themselves require no sanding before and after. In fact, by covering up the light and dark patches formed when the sanding cut through, you can get away with applying fewer coats. 


Metal primers contain a significant amount of anti-corrosive pigments that can stop the metals from developing rust. They are also colored to complement the shade of rust.

At the same time, the pigmentation in timber primers can shield the substrate from damaging UV light. Quality wood primers can even stop molds from growing. 

In some cases, primers can chemically decompose after coming in contact with the wrong surface. So, to get the best out of your primers, you need to choose one that is the most compatible. 

The UV resistivity and rust resistivity of sealers are not prominent. At best, they can prevent the alkyd-type paints from leeching into concretes and other wood composite materials.  

Indoor vs. Outdoors

Most sealers are made for both interior and exterior use. Except for the possibility of leaving a harsh smell for some time inside, their functionalities perform equally well everywhere. 

Unlike sealers, indoor and outdoor primers have different compositions. It would be best if you used an exterior primer outdoors and an interior primer indoors as they cannot survive varying elements of both environments.

Exterior primers can withstand harsh weather conditions and fluctuating temperatures easily. You can use exterior primers inside, but they contain additional functionalities that are unnecessary, especially at the worth of their high price. 

Can I Use a Primer Instead of Sealer? 

I cannot emphasize enough how important it is to apply a primer before painting. You can use a sealer as a primer, but not the other way around. 

If you are worried about the cost, you can go without a sealer. It is not highly recommended as it can compromise the quality and durability of your paint job.

When forgoing a sealer, one must pay special attention for the primed surface to be completely even. Even the color tone needs to be the same throughout to make it easy to paint. 

Be that as it may, sealers have many benefits, and you can even use them as a primer. They are adhesion promoters and can stop the paint from lifting besides ensuring the usual functionalities. 

And if you want to go an extra step further, you can also try undercoating! Undercoating is an optional step performed before painting to enhance the bonding between prep coats and topcoats. 

Final Words

There you have it, the differences between primers and sealers. Although the words are often used interchangeably for both products, there are key differences among them.

In the battle of sealer vs. primer, the former performs better and has more features than the latter. 

Fortunately, most paint companies now sell three-in-one prep coat products that will give you the best value for money. You can finally put all your confusion to rest!

Leave a Comment

Your email address will not be published.

Scroll to Top