There are two main types of paint primer; oil-based primer and water-based primer. So what’s the difference between both products?
The main difference between both primer products is the primer base. Oil-based primers include natural or synthetic oils in the primer coating to keep the paint flowing. Water-based primers on the other hand contain water.
Since water-based primers use water, the primer coating is bound to evaporate and dry quicker than oil-based primer coating.
Water-based primers are suited to water-based paints and paint jobs where preparation is required. Oil-based primers are more suited to enamel paints and paint jobs where sealing, durability, and water-resistance are required.
What is a Water-Based Primer?
Water-based primer (latex primer) is an undercoat that is used for prepping surfaces before applying latex, acrylic, or any other water-based paint.
As the name connotes, water-based primer uses water as the solvent. This means that the primer is easy to clean and you don’t have to use any solvent for that. Also, since the primer is water-based, the coating dries quickly.
Water-based primers can be re-coated with finish paint in less than an hour. The water-based nature of the solvent means that it can be used for both water-based and oil-based paints.
Water-based primer is commonly used for areas that require prep work before painting. This is because water-based primers can be easily sanded or shaped to bring out the desired finish. This type of primer has a low level of VOCs (volatile organic compounds) which means fewer paint fumes.
The low level of VOCs makes water-based primers ideal for indoor use. The primer is commonly used to coat furniture, indoor walls, and is also common for murals and artwork.
However, water-based primer has a flaw. The primer is not very good at sealing materials and as such is more suited to non-porous material.
What is an Oil-Based Primer?
Oil-based primer is an undercoat that contains a high volume of oils. Oil-based primer is used for sealing glossy or oil-based paints, blocking stains, and stopping color from bleeding through.
Oil-based paint is good for blocking stains because it has compounds like shellac in the coating, plus naturally it’s a very thick primer.
Oil-based primers aren’t common on surfaces that require prep work like sanding. This is because the primer coating when dry is usually hard and rigid. As such, sanding or shaping it without damaging the primer coating will be very difficult.
However, oil-based primer has one flaw. The primer is known to host a high volume of paint chemicals and VOCs leading to the release of offensive odor when used.
Oil-Based vs Water-Based Paint Primer: Head to Head
Let’s check out how both paint primers compare to each other using their varying features and paint formulas.
The Paint Formula
Water-based primer is based on water. This means that the solvent in the primer coating is water while oil-based primers use oil-based solvents like linseed oil. The main reason both primers have different features is because of the base.
Asides from that, water-based primers have a low level of paint chemicals and VOCs. Most water-based primers are made from solvent, colorants (usually white or grey), and the binder.
On the other hand, the oil-based primer has other chemicals aimed to block stains and improve the adhesion of the primer coating.
Dry and Cure Time
Water-based primers are known to dry quickly because of the nature of the primer. For the primer to get dry, the solvent has to be evaporated.
Since water-based primers use water, the solvent will evaporate quickly. On average, water-based primers can be re-coated in 30 minutes and can be sealed with finishing paint in an hour.
Oil-based primers take longer to dry. This is because the primer uses oil as the solvent and oil takes longer to evaporate and dry than water. On average, oil-based paints will need at least 2 hours before being sealed with finish paint.
In terms of paint adhesion or bonding, oil-based primers are better. Water-based primers also bond but not as well.
However, in terms of material adhesion, water-based primers will bind to several types of materials better than oil-based primers.
The Type of Paint Used For
When it comes to the type of paint you can use the primer for, water-based primers are better. Water-based primer is more accommodating or absorbent since the primer is water-based.
This means that any type of paint can be used over the primer coat and there will be good adhesion. However, water-based primers don’t go well over oil-based paint. So you’ll need to sand before using it.
Oil-based primers are picky when it comes to paint types. Oil-based primers are more suited as an undercoat for enamel, epoxy, and other types of oil-based paint.
Oil-based primers last longer than water-based primers. The main reason for this is that oil-based primers have additives that preserve the primer coating.
Also, oil-based primers are moisture and UV-resistant meaning that the primer is less prone to damage.
Water-based primers also last long, especially when sealed with a tough top coat. But ordinarily, the primer is not as durable as oil-based primer given that water-based primer contains fewer additives.
Related Read: Does Primer Go Bad?
Indoor or Outdoor Use
Water-based primers are suitable for both indoor and outdoor surfaces. However, water-based primer is better used on indoor furniture and walls. This is because the paint primer isn’t very durable. Also, water-based primer has a low level of chemicals and VOCs so it’s safer and more ideal for indoor use.
You can use water-based primer on outdoor material too but the primer coating must be sealed with moisture and UV-resistant top coat. Oil-based polyurethane will be a good pick.
For oil-based primers, you are better off using them outdoors due to the high level of chemicals and VOCs. If you use oil-based primer indoors, ensure to do so in an open space if not, you’ll increase the chances of a build-up of paint fumes and VOCs. Oil-based primers are also more durable and weather-resistant and as such, more ideal for the harsh exterior environment.
Water-based primers are easier to clean than oil-based primers. In most cases, all you need to clean water-based primer is a clean rag and warm water.
For tough stains, a bit of dish soap will do the trick. For oil-based primers, you’ll need a solvent like turpentine or mineral spirit to clean.
Sealing and Blocking
If the material is damaged by water, stains, or oil, you need to prime first to seal the stains so they don’t bleed through the finish paint. Oil-based primers do a better job at this than water-based primers.
Oil-based primer due to the thicker nature of the coat and the chemicals in the formula is more suited to blocking stains and moisture from bleeding through the finish paint.
Water-based primers don’t seal stains very well because the primer coating is water-soluble and porous. As such, the primer coating will allow paint and stain to bleed through.
Oil-based primers have a harder texture when dry. The hard texture is gotten from chemicals and binders in the primer coating. As a result of the hard texture, sanding is more difficult. It’s also less likely to be able to shape the primer coating once it has dried.
Water-based primers have a flexible texture. The primer coating is not as hard given the absence of chemicals in the primer. As such, it’s easier to sand, distress, or shape the primer coating before putting paint over it.
Use on Wood
For wood, oil-based primer is better especially if it’s porous wood. Oil-based primers are better at sealing wood grain and preventing paint from being sucked into the wood.
Water-based primers are more suited to sealed or non-porous material. Since the primer coating can’t seal the wood grain, it will just penetrate leading to more coats of primer needed and a longer dry time.
Here is a table that highlights the differences between oil and water-based primers:
|Water-based primer||Oil-based primer|
|Clean-Up||Easy||You’ll need a solvent|
|Dry-Time||30 minutes to 1 hour||About 2 hours|
|Type of Paint Used For||All types of paint||Oil-based paints|
|Stain-blocking and Sealing||Poor||Great|
Now that you know the differences between both primers, which one do you need? Let’s find out.
When Should You Use Water-Based Primer?
You should use water-based primer when you are:
Painting an Indoor Object
If you want to paint an indoor wall, furniture, room, or toy, water-based primer is ideal. The primer is safer given the low level of VOCs.
Using a Water-Based or Latex Paint
When you plan on using latex, mineral, acrylic, chalk, or any other water-based paint, always use a water-based primer.
Doing a Lot of Prep Work
For construction areas or paint jobs where you are renovating, reshaping, or doing any task that will require lots of prep work, use a water-based primer.
The coating is easier to clean, sand, shape, and even paint over so it makes your workload easier. With an oil-based primer, you’ll spend a lot of time on prep work.
In Need of A Quick Drying Primer?
Use water-based primer since it dries quicker. You can successfully re-coat water-based primer with finish paint in an hour. Oil-based primers will take longer.
When Should You Use Oil-Based Primer?
You should use oil-based primer when:
You Want To Seal or Block Stain
If the surface to be painted is defected, stained, or damaged by moisture, you’ll need an oil-based stain-blocking primer to prevent the stain and moisture from bleeding through the finish paint. Water-based primers will just let the stain and moisture pass through after a while.
You Are Dealing With An Oil-Based Paint
If you are using an oil-based paint, you should use an oil-based primer. If you want to paint over oil-based paint, you should also use an oil-based primer too.
You Want Water-Resistance
Oil-based primers prevent water or oil from penetrating so for surfaces that will require water resistance, oil-based primers are ideal. Oil-based primer is also ideal for exterior use.
Can You Use Oil-Based Primer Over Water-Based Primer?
Yes, you can use oil-based primer on top of water-based primer. Oil-based primer can also be used as an undercoat for water-based primer or paint. You can also use water-based primer over oil-based primer or paint.
Why Should You Use Primer?
You should use primer for every painting project. Primer will help the paint adhere better to the surface. Primer will also block stains and bleed-through.
How Many Coats of Primer Do You Need?
The number of coats for primer depends on the material you are painting. However, as a rule of thumb, you need 2-3 coats of primer.
Overall, oil-based and water-based primers are both great choices but the best one for your task depends on the task and your taste.
Remember, use water-based primer for latex paint and indoor surfaces. Oil-based primer is more suited to enamel and exterior surfaces.