If you’ve been considering switching to oil-based paint, you may be wondering the best way to do it. Whether you’ve attempted to switch or are still thinking it over, it’s essential to know the rules of painting for both oil and latex paints.
Knowing the flexibility of these two paints and what can and cannot be done with them will help you get the best possible finish for whatever project you plan to take on next.
As a general rule, if you want to apply an oil-based paint over latex, you will have to do a lot of sanding and priming. While oil-based paint will not stick to latex directly, the switch can be done in as few as six steps.
Applying paint correctly and getting a good finish can be a challenge, and it can be incredibly stressful to understand the differences between your paint options and their benefits.
To figure out how you can apply an oil-based paint over latex, what happens when you do so, and how to get the best possible finish read on.
What Happens If You Put Oil-Based Paint Over Latex?
As a whole, latex-based paint is not excellent for adhesion, so the oil-based paint will crack and split unless you go through the process of sanding and priming the latex paint. We will provide a thorough explanation a little later in this article.
Latex paint has many qualities, including:
- Water solubility and resistance
- Great substrate adhesion
- Fading and chalking resistance
While latex is an excellent option for those who want an easy paint job from start to finish, you might opt for oil-based paint for more durability. Oil-based paint’s adhesion to the more challenging surfaces such as:
According to Glidden, a smoother finish and abrasion resistance is why it’s often chosen over latex.
In this case, the qualities of latex paint can make it difficult to paint over. Because of the latex paint’s flexibility and its fast drying time, the coats it creates will often shrink and tend not to adhere well.
This low adhesion and shrinking can lead to cracks and splits in the new oil-based coats.
How To Tell if Paint is Latex or Oil Based
The three ways to determine if your paint is oil or latex-based are:
- Looking at old paint can labels
- Using the adhesion test
- Using the acetone test
Before engaging in the process of preparing your surfaces for new oil-based paint, you will want to be sure that the paint already on your surface is latex.
You may mistake an oil-based paint for latex because it isn’t always as easy as simply eyeballing the surface. Luckily these tests will prevent that.
Look For Any Leftover Paint Cans
The first and most straightforward way to see what kind of paint is on your walls is by looking for any used or unused paint cans left behind. The labels of paint cans clearly state if your paint contained is oil or latex-based.
So, save yourself the trouble, and before doing any of these tests, take a good look around to be sure there are no leftover paint cans you can read as you may not have to do any of these tests.
If you don’t have any paint cans to check, you can start with an adhesion test. For this test, you will have to have a small amount of unused latex paint. The adhesion test, also known as a scratch test, is simple to determine if your paint is oil-based.
Pick an inconspicuous area like a closet door jam and apply a small amount of latex paint. Allow the freshly painted area to dry. It’s best to leave it overnight and check back in the morning.
After it’s dried, scratch the area where you applied the latex paint. Because of the poor adhesion latex has with oil paint, the latex paint will scratch right off if your paint is oil-based. If the paint does not scratch off its oil-based
The next test is the most reliable, and it’s the acetone test. For this test, you will need a cotton ball and a liquid containing acetone.
First, use a cotton ball to soak up the acetone. If you don’t have plain acetone, you can also use rubbing alcohol or nail polish remover as an acetone alternative. Just be sure the item you’re using does not say acetone-free.
Next, you will rub the cotton ball on the painted surface in question. If the paint remains intact and nothing happens after rubbing the cotton ball on it, the paint is oil-based. If the paint gets soft and rubs off, the paint is latex.
How to Apply Oil Paint Over Latex
To apply oil paint over latex.
- Sand surface to a matte
- Sand your surface to smooth
- Mask your edges
- Apply your topcoat
- Remove masking tape
As you know, oil-based paint cannot be directly applied over latex paint. Because latex paint does not have excellent adhesion, the oil-based paint will chip and crack.
But, oil-based can be applied over latex if you properly sand and prime your surface using the six-step process below.
- Sand Your Surface to A Matte
Your oil-based paint will not properly adhere because of the latexes’ flexibility. The stretchy nature of the latex will make it impossible to apply the paint directly.
The first and most crucial step is sanding down your surface. This step aims to remove as much latex as possible from the surface, so experts recommend using p80 grit sandpaper with a sanding block.
We are trying to achieve a matte look, and any shiny areas must be sanded down to avoid future problems with your oil-based coats. This first step will be time-consuming, but the result will be less desirable if it is not executed thoroughly and with attention to detail.
- Sand Your Surface Until It’s Smooth
You will now be sanding again, but this time you’ll be using 150 grit paper. Once you’ve sanded with this paper thoroughly, you’ll want to wipe away the left behind dust, and this will achieve a smooth surface.
Clean the surface with a wet cloth and let it completely dry before moving on to the next step. If your surface is not dry, then the next step of the process won’t work, so be sure you’ve given the surface enough time to dry.
- Mask Your Edges
Like in all other painting jobs, you want to protect areas not meant to be painted. The edges of things will need to be covered with masking tape, like:
- Light switches
This masking allows you to get clean lines and a professional look.
- Prime Your Surface
A primer is necessary for all painting jobs because it improves paint adhesion, and the primer seals your porous surfaces. A water-based or acrylic primer is best because both are compatible with latex.
With this step, you are trying to cover as much of the latex as possible so use two coats of primer. By completely covering the latex, you ensure your oil-based paint doesn’t react to the old latex paint.
- Apply Your Topcoat
Finally, you will apply your topcoat. After painting the initial coat and giving it time to dry, you may look at your surface and decide you need another coat.
A topcoat is not something you want to skip for the best possible coverage, a clear color, and no streaks.
- Remove The Masking Tape
The final step is, of course, removing your masking tape. You will want to do this step while your final paint coat is still a bit wet, and this is to avoid tearing off, breaking, or chipping any dry paint.
Things to Remember About Oil-Based Paint
While switching to an oil-based paint may be the best choice for you, there are some things you should remember about it before committing to the switch. The qualities of oil-based paint are different from those of latex, and there are added benefits and difficulties that come with the switch.
Oil-based paint is well known for its extremely long drying time. While oil-based paints generally take around eight hours to dry, latex paints take four hours.
This means that if you plan to recoat, you will have to have a lot of patience. While it makes for a slower process, it also has a much smoother finish and flow than latex paint.
Ventilation Is A Must
According to HGTV, oil-based paint fumes can be extremely overwhelming.
Open windows and fans are a must when painting with oil-based paint. You will need far more ventilation with oil-based paint than you will the latex.
The Volatile Organic Compounds (VOCs) are much higher in oil-based paints than latex, and to maintain proper safety, fresh air needs to be able to get rid of them.
Dark Areas Tend to Yellow
If you look at the baseboards in your closets, they are likely to be yellow if painted with oil-based paint. Oil-based paints that are light in color yellow in dark areas as the paint ages.
But, the more it’s exposed to sunlight, the less yellowing you will get. Similarly, exposure to sunlight can reverse the yellowing.
While today’s paints are much better about holding color, this yellowing can still be a problem with the look of your paint job over time.
When oil-based paint is used outside, it’s common for it to grow mildew. Mildew is particularly prevalent in warm and damp climates, and this is especially true for paints that contain large amounts of linseed oil because it is a food source for mildew organisms.
A Specific Brush is Required
Different brushes are required for different kinds of paint. While brushes are available that work well for both latex and oil, natural bristle brushes work a lot better than other multi-use brushes when painting with oil-based paints.
According to Purdy, white bristles are better for painting smoother surfaces because they are supple and soft.
Black bristles are best for textured surfaces because they have better abrasion wear and are stiffer. These brushes usually say they are for oil-based paints on the handle.
A Hard Finish
One of the drawbacks people have found with latex is that creating a hard and durable finish can be challenging. But, there is no better finish with oil-based paint, and the hard finish of oil-based paint makes it the best for windows and doors.
The sticking that results from using latex paint on these surfaces is eliminated. While a hard finish is excellent, it can lead to chipping and cracking because it does not have the flexibility of latex paint.
It’s essential to keep in mind that surface expansion and temperature swings can eventually break the film.
Clean Up is Difficult
The process of cleaning up an oil-based paint is more involved than that of other paints because of its durability. Because oil-based paint is not water-based, it can be cleaned and mixed with water, but water cannot break down the paint for removal.
Mineral spirits and paint thinners must be used to clean your brushes. Some tips for mineral spirits and paint thinners are:
- Use a well-ventilated area
- Be sure to vigorously mix your brush for at least a minute
- Portions that are not used go into a container that’s sealable and metal
- The brush cleaning process should be repeated until the mineral spirits are clear
- Mineral spirits and thinners should be disposed of at a landfill’s hazardous waste dropoff
In conclusion, latex and oil don’t mix. But, it’s entirely possible to go from latex-painted walls and surfaces to oil-based.
By taking your time to sand, prime, and prepare for new paint and understanding the qualities of both the latex and oil-based paints, you will achieve a great finish.