Determining which type of paint is most suitable for your paint project’s needs is an important step in completing your project. Keep reading to learn the difference between water and oil-based paints and also how to determine what current coating is used in/on your house.
Oil-Based vs Water-Based
When referring to whether the paint is oil or water-based, we are talking about the type of solvent used in the paint, i.e. the liquid component of the paint that evaporates as the paint dries. Oil-based paints (sometimes incorrectly referred to as “enamel”) use an organic solvent in the makeup of the paint, typically mineral turpentine. As the name suggests, the solvent used in water-based paint (aka acrylic paints) is almost all water.
Volatile Organic Compounds
If you’re ever bored enough to read your paint can, you’ll often see “low-VOC” printed somewhere on it. What is a VOC and why do you want it to be low? A volatile organic compound (or VOC) is an organic solvent in vapor form. VOCs are the vapors and gasses that are released as the organic solvent evaporates into the air, aka the drying process of paint. An organic solvent is made up of petrochemicals and plants and expels vapors into the atmosphere as it evaporates. This vapor has a strong odor, the classic paint smell we all know (and some love…), is flammable, and can have a harmful effect on the environment and our health.
High exposure to these VOCs can cause headaches, skin irritation, and nausea for some, which is why it is important to ensure there is very good ventilation and airflow present when painting with oil-based paint.
As water-based paints feature solvents that are primarily made up of water, they
release much fewer VOCs into the air and are therefore considered better for the environment and likewise better for our health.
Characteristics of Oil-Based and Water-Based Paints
Sheen Levels and Duration
Oil-based paints can achieve a higher sheen level (glossier) when applied due to the makeup of the paint; however, the sheen can become duller over time. While water-based paints achieve a lower sheen finish, they can typically maintain this sheen level over a longer period of time.
Typically, oil-based paints dry harder which means excellent resistance to wear and tear. However, there is not a lot of flexibility within the paint, which means oil-based paints are more likely to become dry/brittle, crack, and chalky over time. Oil-based paints are also known to yellow over time due to its components. Nowadays there have been many developments that allow water-based paints to dry harder and be effective when resisting damage and wear. The flexibility afforded to water-based paints mean that they are able to expand and contract with weather conditions. This makes them less susceptible to cracking.
Water-based paints perform great on exterior surfaces. This is because they are much more resistant to UV rays, allowing them to retain sheen levels and color over long periods of time. The flexibility in the paint makeup means the paint can move with the substrate as it expands and contracts in different weather conditions, which is exactly what you want for exterior surfaces. Oil-based paints do not perform well in exterior conditions as it breaks down in UV light and develops a chalky surface. As there is little to no flexibility within the paint, it is not able to expand and contract in differing weather conditions, making it more susceptible to cracking.
Clean Up & Application
Water-based paints do not perform as well when applying paint in adverse weather conditions. Humidity and lower temperatures can extend drying times, whereas much higher temperatures can cause the paint to dry too quickly. Water-based paints drying too quickly or too slowly can have an impact on the finished result, as well as the long-term performance of the paint.
On the other hand, oil-based paints are much more tolerant of differing weather conditions, and therefore extreme temperatures and humidity do not have as much impact on the application, drying times and long-term paint performance.
Water-based paints can tolerate small amounts of moisture on a surface prior to application, since the paint is able to absorb the moisture. This will thin the paint out ever so slightly, but will not affect its ability to create an adhesion bond to the surface.
As oil-based paints repel water, the paint is unable to create a strong adhesion bond to the surface. As a result, any substrate that oil-based paint is applied to must be completely dry before application or it will not bond properly.
Oil-based paints are typically slower to apply than water-based paints, as the paint has a stickier and thicker feel to it. During the painting process, oil-based paints are responsible for the emission of high VOCs, which creates that strong “fresh paint smell”. As water-based paints contain substantially less VOCs, the smell is not as strong.
Oil-based vs water-based paint drying times are also very different:
Water-based paints are much easier to clean up due to the solvent being mainly water, and brushes and painting accessories can be typically cleaned with water. Oil-based paints require turps or other specialty thinners to be used in the clean-up process.
Which type of paint do I have in/on my house?
The test to determine whether your paint is oil-based or water-based is pretty simple. Put some methylated spirits (denatured alcohol) on a rag and wipe at a small section of your wall. If the cloth is stained with the wall color, it is water-based. If it is not stained with the wall color, it is oil-based. Ta-da! The more you know.
Note: If you wish to repaint your existing oil-based wall with water-based paint, sand back the wall with sandpaper to remove the sheen. Apply an undercoat to the substrate, allow it to dry, and coat with your new water-based paint.
Talk to the pros first!
We highly recommend you schedule a quick consultation with Brown’s Family Painting to have a chat with the experts before you start your next paint project. They will be able to answer any questions that you might have, and be able to give advice on choosing the right type of paint for your project!