Oil-based or Water-based…that is the Question.
You’re gazing along the aisles of paint, oil and stain products at the local hardware megastore and feeling spoilt for choice.
And your first question is oil-based or water-based? Sounds simple enough, but the answer is not always straightforward.
It depends on what you’re coating and the finish you’re looking for.
It’s all about the solvent
The terms oil-based and water-based refer to the solvent that’s used in the product. The solvent is what evaporates during the drying process.
Solvents used in oil-based coatings are organic – often mineral turpentine.
The solvent used in acrylic or water-based coatings is virtually all water.
Organic solvents produce vapours known as volatile organic compounds, or VOCs. The characteristic strong odour of oil-based finishes as they are applied and dry is due to the release of vapours containing petrochemical compounds.
While acrylic paints are water-based, most release VOCs but at a much lower level than oil-based products.
Both have their place
Acrylic or water-based paints have become widely used in many applications over recent decades. The technology has come a long way.
Because of their ease of application and the convenience of cleaning up with water, they’re the preferred option for the majority of household applications.
There’s certainly a place for oil-based products. For enhancing timber, many people prefer the rich look and finish of oil, which penetrates deep and highlights the natural colour.
If you’re priming ferrous metals, such as steel, oil-based primers are essential.
But for most surfaces, acrylic finishes will last longer because of their greater elasticity and ability to withstand expansion and contraction of building materials with changing temperature.
Oil-based coatings dry harder and, initially, can produce a higher gloss look than acrylic coatings. For interior applications where you want to feature a stunning high-gloss look, such as on skirting boards or furniture like timber chairs and stools, an oil-based paint might be perfect. But particularly with exposure to the elements, the sheen gets duller with age.
Acrylics in the great outdoors
Acrylic finishes perform superbly on exterior surfaces. They retain their sheen over many years because of their superior resistance to UV radiation, and their ability to expand and contract with the substrate in different weather conditions.
Oil-based paints are not so resistant to UV radiation and will break down with constant UV exposure over time, causing the surface to become chalky.
Acrylic-based coatings can be applied to surfaces with a small amount of moisture present. This is not the case with oil-based coatings – they will not bond properly with the surface if there is moisture present.
The drying game
Acrylic paint is considerably quicker-drying than oil-based paint, but particularly when painting outside, you need to carefully pick your days when using acrylic products. In the heat they can dry too quickly, and in the cold or where the humidity is high, they might take an extended period to dry. Either of these scenarios can compromise the look and durability of acrylic paints.
For the most part, drying times of oil-based finishes aren’t impacted by different weather conditions. And while they might dry harder, their relative lack of flexibility means they typically crack, go brittle, flake and weather more readily.
The right products and advice
So while acrylic paint might be the solution for most of your needs around the home, think horses for courses – there are times when oil-based finishes are the preferred option.
And when you purchase from your local Paintright store, you know you’ll not only pick up quality products and accessories – there’s also a heap of friendly, well-qualified advice on hand to ensure you get the job done right.