Polyurethane is one of the strongest finishes in the painting world. But there are two types of it; water-based and oil-based. So what’s the difference between them?
Water-based polyurethane uses water as its solvent, while oil-based polyurethane uses oil (natural or synthetic). The solvent (oil or water) must evaporate for the finish to dry. Since they have drying times, both types have different features.
The difference in the solvent also means they have a different finish. Water-based has a dry textured finish, while oil-based has a glossy finish because of the high amount of oils it has.
Water-based is a fast-drying finish. Once the water evaporates from the coating, it dries to form a hard and moisture-resistant coating. On average, water-based polyurethane dries enough for a re-coat within 8 hours.
Water-based poly doesn’t yellow over time because it has fewer additives in its formula than oil-based poly. However, water-based poly is less durable and more prone to scratches than oil-based polyurethane. So, it’s not a good option for high-traffic foot floors.
Use water-based polyurethane if:
- Painting Indoor Surfaces – Water-based polyurethane is better for indoor surfaces because it dries faster and doesn’t yellow over time.
- Clean Up – If you are painting a surface that attracts dust and grime, use water-based polyurethane as it’s easier to clean.
- Thin Coats – If you need to touch up or fix a surface, use water-based polyurethane as it has a light flow.
Oil-based polyurethane uses natural or synthetic oil as its solvent. Once the oil evaporates, the finish becomes dry and forms a hard glossy moisture-resistant layer.
Since oil takes longer to evaporate, this sealant has a longer dry time. On average, it takes oil-based polyurethane 24 hours to dry enough for a re-coat and 48-72 hours to cure.
It has a thick flow, so you need fewer coats to cover a surface. However, its finish can turn yellow if you apply too many coats.
Use oil-based polyurethane if:
- Outdoor Surfaces – For outdoor surfaces, use oil-based polyurethane. because it’s more durable and has a stronger coating.
- Floors – Use it for floors exposed to moisture, high foot traffic, and extra weight.
- For Tabletops – Countertops and tabletops are exposed to scratches, spills, and moisture. So, you must use it for these surfaces.
Oil-Based vs Water-Based Polyurethane: Head to Head
Let’s see the differences between these two finishes by comparing them:
The Paint’s Base
Water-based uses water as its solvent, while oil-based polyurethane uses natural or synthetic oil, such as linseed oil. The paint base (or solvent) determines the features of these two sealants.
Water-based dries faster than oil-based polyurethane. On average, water-based polyurethane dries enough for a re-coat for 8 hours, while oil-based needs 24 hours.
Polyurethane dries through evaporation. Since water evaporates faster than oil, this means water-based dries faster.
When dry, oil-based polyurethane is harder than water-based. This is because oil-based polyurethane dries slower, so the coating has more time to harden. The longer the finish takes to dry, the more time the paint particles have to harder.
Oil-based polyurethane lasts longer than water-based polyurethane because it has a stronger, glossier, and more rigid coating. On average, it lasts 10 years, while water-based polyurethane lasts 5 years.
Indoor or Outdoor Use
You can use both types indoors and outdoors. However, water-based polyurethane is more suited for indoor use, while oil-based is more suited for outdoor surfaces because of its hard and rigid layer.
Clarity Of The Finish
Polyurethane is a clear coat, meaning it doesn’t have paint pigments, so the finish has no color. But, over time, the oil-based polyurethane tends to yellow, while water-based doesn’t.
So, the water-based will have a clear finish for years, while the oil-based will start to yellow over time due to the oily deposits on the coating.
Oil-based is thicker than water-based polyurethane. because it uses oils as a solvent and has more additives in the formula.
Oil-based polyurethane protects the wood better than water-based because it has a stronger and harder coating due to its slow dry time. So, oil-based is less likely to be affected by dents or scratches.
Water-based polyurethane is easier to apply because it has a lighter flow that you can control easier. Also, the fast dry time of water-based allows you to complete a painting project faster.
On the other hand, oil-based polyurethane has a thick flow and is more likely to reveal brush marks. Also, since the finish takes longer to dry, it attracts more dust while drying.
Oil-based polyurethane covers a surface better because it has a thick flow. A single coat of oil-based polyurethane covers more surface than 2 coats of water-based polyurethane (approximately).
So, you need more coats of water-based than you need for oil-based polyurethane.
Water-based and oil-based polyurethane are two durable topcoats used to protect surfaces from moisture, water, scratches, and other damages.
But, the main difference between these two types is the solvent. Oil-based poly uses oil as its solvent, while water-based poly uses water as its solvent. The difference in the solvent means these two polyurethanes have different drying times.