Polyurethane is one of the strongest finishes in the painting world. But there are two types of polyurethane; water-based and oil-based polyurethane. So what’s the difference between both types of polyurethane?
Water-based polyurethane uses water as the paint’s vehicle. The polyurethane resin is dissolved in water. When the paint is applied and the water is evaporated, the polyurethane finish will appear.
On the other hand, oil-based polyurethane uses synthetic or natural oil as its solvent which means the polyurethane resin is dissolved in oils.
The differences in paint solvent mean that water-based polyurethane will dry faster than oil-based polyurethane but oil-based polyurethane will prove stronger (due to longer dry time).
But these are just some of the differences between both types of polyurethane. Let’s dive deeper. First, let’s check out water-based polyurethane.
What Is Water-Based Polyurethane Used For?
Water-based polyurethane is distinct because the paint uses water to carry the polyurethane compounds and prevent solidification inside the container. When the water inside the polyurethane paint coating is fully evaporated, it will dry to form a hard and moisture-resistant layer.
Since the polyurethane is water-based, it will dry quickly. On average, water-based polyurethane dries completely in 8 hours while curing can take a few more hours or days. Water-based polyurethane also has a lower level of toxicity.
Asides from being non-toxic, water-based polyurethane can be applied in multiple coats. Since the paint dries quickly, you can apply more coats in less time. Water-based polyurethane is also very easy to maintain and clean.
Most stains can be wiped off with a damp rag. Water-based polyurethane is also very common for retaining its clear finish for long periods. Unlike other sealants that turn yellow after a while, water-based polyurethane remains clear.
However, water-based polyurethane has a flaw. The paint is less durable and more prone to scratches and claw marks. So it’s not the perfect choice on floors in homes with pets.
What Is Oil-Based Polyurethane Used For?
Oil-based polyurethane uses either natural or synthetic oils as the paint’s solvent or vehicle. When the oils are fully evaporated, the paint will become dry and reveal a hard and moisture-resistant layer.
Since the polyurethane is oil-based, it takes longer to dry. Oil-based polyurethane will even take longer to cure and harden. The oil-based nature of the polyurethane also means that the paint has a higher volume of chemicals. These chemicals produce a strong odor when they react with the atmosphere.
Oil-based polyurethane has a thick flow which means you need fewer coats of the paint to cover a surface. This also means that oil-based polyurethane has great coverage.
However, oil-based polyurethane also has a flaw. The paint can be toxic in large amounts as the paint is formulated with chemicals.
So how good is water-based polyurethane when compared to oil-based polyurethane? To figure that out, we’ll have to compare both types of polyurethane using their features.
Oil-Based vs Water-Based Polyurethane: Head to Head
Here is a table indicating the differences between oil-based and water-based polyurethane.
|Water-based Polyurethane||Oil-based Polyurethane|
|Paint base or solvent||Water||Natural or synthetic oil|
|Dry-time||2 - 4 hours||3 - 8 hours|
|Paint hardness||Moderate||Very hard|
|Indoor or outdoor use||Indoor use||More suited to outdoor use|
|Paint thickness||Light flow||Thick flow|
|Cure time||24 - 48 hours||72 hours and above|
Let’s go into detail.
The Paint’s Base
The paint’s base refers to the solvent or thinner used in the paint. In water-based polyurethane, the paint base is water. In oil-based polyurethane, the paint base is a synthetic or natural oil.
Many brands use linseed oil as the solvent in oil-based polyurethane. The paint’s base is what affects other features of both paints.
How long does it take for the polyurethane to dry?
Water-based polyurethane dries faster than oil-based polyurethane. On average, water-based polyurethane will get dry enough to touch in less than 2 hours. The paint can be re-coated in less than 4 hours and it cures in about 24 hours.
Oil-based polyurethane on the other hand will take at least 4 hours to dry. For a re-coat, you’ll have to wait about 6 hours. It can take up to a week for oil-based polyurethane to fully cure.
How hard is the paint coating when it dries?
When dry, oil-based polyurethane is usually harder than water-based polyurethane. The reason for this is that oil-based polyurethane dries slowly.
Since the paint takes longer to dry, the paint particles have more than enough time to bind and harden or cure. Oil-based polyurethane can deal with weight and foot traffic.
How long does the polyurethane finish last?
Oil-based polyurethane tends to last longer than water-based polyurethane. On average, oil-based polyurethane lasts up to 10 years.
Water-based polyurethane doesn’t usually last that long. The main reason oil-based polyurethane lasts longer is that the paint is harder and less likely to be affected by the elements.
Indoor or Outdoor Use
Should the polyurethane be used indoors or outdoors?
Though both types of polyurethane can be used indoors and outdoors, water-based polyurethane is more suited for indoor use. This is because the paint has a low volume of paint chemicals so it’s less likely to produce a strong odor indoors. Oil-based poly can cause a toxic odor if used in large amounts indoors.
However, oil-based polyurethane can be used outdoors. The high volume of paint chemicals and additives in the polyurethane means it can withstand the harsh exterior environment. You should know that you can also use water-based polyurethane outside but ensure to use exterior water-based polyurethane.
Clarity Of The Finish
Polyurethane is a clear finish but which type is clearer?
Both oil-based and water-based polyurethane produce clear finishes initially. But, over time, oil-based polyurethane will begin to yellow. This is because there were oily deposits left in the polyurethane coating after the oil was evaporated.
These deposits produce yellow tints in the clear finish after a few years. Also, the chemicals in the oil-based polyurethane can react causing yellow stains in the paint.
Water-based polyurethane remains clear because there are no oily deposits in the paint. You should know that water-based polyurethane can also yellow after a while. But, this is usually due to external factors and not the paint itself.
Oil-based polyurethane is thicker than water-based polyurethane. This is because of the oils present in the paint.
How well does the polyurethane protect the wood?
Oil-based polyurethane is more protective than water-based polyurethane. This is because oil-based polyurethane dries slowly and hard. So the paint is less likely to be affected by dents and scratches.
Since the paint is hardly affected by scratches, the material underneath will be protected. Water-based polyurethane will also protect your surface brilliantly. It just doesn’t offer as much protection as oil-based polyurethane.
How toxic is the polyurethane?
Oil-based polyurethane is more toxic than water-based polyurethane. This is because oil-based polyurethane contains chemicals and resins.
When the paint is laid, these chemicals react with the atmosphere and produce a strong odor that can turn toxic in large amounts. Water-based polyurethane has a very low level of chemicals which means the paint is less likely to turn toxic.
Water-based polyurethane is easier to apply than oil-based polyurethane. This is because water-based poly dries quickly so you can easily shape the finish and apply multiple coats. Water-based polyurethane can also be sprayed, rolled on, or applied with a synthetic-bristled paintbrush.
Oil-based polyurethane on the other hand isn’t that easy to apply. The thick nature of the finish means that it’s likely to reveal brush marks. Also, since the paint takes long to dry, it’s more likely for dust to settle on the finish.
Also, using a roller to apply oil-based polyurethane isn’t the best idea because the paint will be too thick. You should use a natural bristled paintbrush to apply oil-based polyurethane.
How well does the polyurethane cover the surface?
Oil-based polyurethane has more coverage than water-based polyurethane. This is because oil-based polyurethane is thicker.
A single coat of oil-based polyurethane is equal to at least 2 coats of water-based polyurethane. So you’ll need more coats of water-based polyurethane to cover a surface.
So when should you use water-based polyurethane? Let’s find out.
When To Use Water-Based Polyurethane?
You should use water-based polyurethane instead of oil-based polyurethane in the following cases:
When Painting Indoor Furniture
Water-based polyurethane is great for indoor furniture due to its low level of toxicity and clarity of the finish. Water-based polyurethane will protect the wood while also showing the texture of the wood grain.
You can even tint water-based polyurethane by adding colorants or acrylic paint to the polyurethane. This will create a perfectly colorful and durable finish.
When Paint Clean Up Matters
If you are painting over an area that you know will attract dust and grime, it’s better to use multiple coats of water-based polyurethane.
This is because water-based polyurethane is easier to clean and you can easily wipe off stains on the surface with a damp rag.
You’ll need a solvent to clean stains off oil-based polyurethane. And, if you keep cleaning the paint with a solvent, it’s only a matter of time before the finish wears off.
When You Want Thin Coats
Since water-based polyurethane is thinner than oil-based polyurethane, it’s ideal for tasks where thin coats are needed such as touch-ups and quick fixes.
So when do you use oil-based polyurethane? Let’s find out.
When To Use Oil-Based Polyurethane?
You should use oil-based polyurethane instead of water-based polyurethane:
When Painting Outdoor Furniture
When finishing outdoor furniture, it’s best to use oil-based poly as it is more equipped to handle the harsh exterior environment.
When Painting Floors
The harder finish of oil-based polyurethane means it’s more suited to finishing floors. Since the paint is hard, it can cope with extra weight and traffic.
When Finishing Countertops and Tabletops
Countertops and tabletops see a lot of action, scratches, spills, and the likes. Oil-based polyurethane’s hard texture makes it thrive on such surfaces.
When Painting Outdoors
Any outdoor finish that you want to put polyurethane on should be coated with oil-based polyurethane. Asides from the strength of the polyurethane that makes it thrive outdoors, it’s also safer to apply oil-based poly outdoors where the paint odor can be dispersed easily.
When There is Time
Since oil-based poly dries slowly, it should only be used when there is time to wait hours for the paint to dry.
Overall, both types of polyurethane are great to use so I know how difficult it is to pick one. But I hope the guide above has made your decision easier.
Remember, water-based polyurethane is more ideal for indoor use since it’s less toxic. Oil-based polyurethane is more suited to exterior use and on surfaces that require protection.