Two of the most common wood finishes are polyurethane and acrylic. So, what’s the difference between them?
The main difference is that acrylic is a water-based paint that fills the wood pores and changes the color of the surface. While polyurethane is a sealant that is used as a final coating and protects the surface from different elements.
Since acrylic paint is water-based, it dries in less than 24 hours. While oil-based polyurethane can take up to 3 days to cure. However, the sealant is stronger and more resistant to moisture.
Polyurethane is a clear synthetic topcoat. It is formulated from the chemical reaction between polyols and (di- or tri-) isocyanates compounds. The chemical reaction between these compounds produces a hard and clear coat known as polyurethane.
When dry, it forms a thick plastic film that protects the surface underneath. The word “urethane” refers to a strong and flexible plastic-like material. Being plastic, its finish is clear and transparent.
However, oil-based polyurethane can develop a yellowish or amber-like tint after a few months, while water-based polyurethane doesn’t. Also, the clear coat can also turn cloudy if the sealant isn’t mixed before application.
You can use polyurethane:
- To protect the wood.
- To prevent moisture damage on wood and wood stains.
- Over other sealants.
- To protect hardwood flooring.
- Over high-traffic areas like tabletops and countertops.
Acrylic is a water-based clear coat used over indoor furniture. Being a water-based finish, it dries within 24 hours. Acrylic paint is beginner-friendly as mistakes don’t affect its finish much. Plus, the paint is much easier to repair than other types of clear finishes.
During the first few hours after application, the paint doesn’t appear clear, instead, it appears cloudy and whitish. But the whitish film becomes a clear coat after it has cured.
Acrylic paint is lighter than other types of clear coats because of its water-based nature. The paint can also be thinned using water. Also, it can give color to wood, which most clear coats can’t. That’s because it can be tinted with water-based colorants and other acrylic paints to give the finish color.
You can use acrylic paint:
- To cover water-based stains.
- Over indoor wood.
- To give color to wood grain.
- To protect wood from blemishes and scars.
Polyurethane vs Acrylic Paint
To find out the superior finish, we’ll use the features of a standard wood finish and see which one is better.
Here is a table that shows the major differences between them:
|The Base||Water and oil-based||Water-based|
|Dry Time||Takes over 24 hours to fully dry||Dries fully in less than 24 hours|
|Clarity of the finish||Oil-based polyurethane develops yellow tint||Acrylic paint remains clear for several months|
|Indoor or Outdoor Use?||Suitable for indoor and outdoor wood||Suitable for indoor wood and furniture|
Now, let’s examine these differences in detail.
The Base and Formula
Polyurethane is usually an oil-based finish made from a large amount of urethane plastic and extra solvents and resins. On the other hand, acrylic is a paint made from pigments and water and is usually water-based.
The Dry Time
Polyurethane takes longer to dry than acrylic paint because its solvent (oil) takes longer to evaporate and its finish forms only after a chemical reaction between polyols and – isocyanates compounds. Since acrylic paint has a simple formula, it will dry quicker.
Acrylic paint dries within 24 hours, while polyurethane takes 3 days to fully dry.
Polyurethane offers better moisture resistance than acrylic paint because it dries harder and it’s difficult for water to penetrate its coating. Also, when dry, it produces a glossy sheen that repels moisture, so it’s even more difficult for water to pass through.
Acrylic paint isn’t as moisture-resistant. Since it is dissolved in water, the paint will start to show signs of damage if exposed to high moisture content for long periods.
Both finishes offer good protection to wood, but polyurethane protects wood better. This is because its finish is harder and can withstand dents, and wood damage, and is moisture resistant. Exterior polyurethane also offers UV resistance to wood.
The Type of Finish
Polyurethane offers a slick glossy finish when dry. The finish makes the wood reflective as the glossy top coat reflects light.
The acrylic finish is not glossy or reflective. The paint offers a dry, textured, and sometimes colorful finish. Since it is water-based, its finish can be thinned with water-based colors to make it colorful and attractive.
So, acrylic paint offers more color and beauty, while polyurethane finish is glossy and hard. But, you can seal the paint to make it more durable.
Purpose and Usage
Because of the hard and moisture-resistant finish, polyurethane is used over high-traffic surfaces. It can be used over floors and surfaces such as patios, walkways, tabletops, desks, stairs, etc. Its exterior type can also be used outdoors.
Acrylic paint is used for low-traffic indoor surfaces such as drawers, cabinets, chairs, indoor furniture, etc. The paint will make indoor furniture appear attractive. You shouldn’t use it outdoors because its finish isn’t strong enough to last.
Cleaning and Maintenance
It’s easier to clean and maintain polyurethane because its finish rarely attracts dust or filth since it is hard and glossy. Also, its finish can be wiped with water and solvents to remove stains and grease.
You’ll be doing more cleaning with acrylic paint because its finish is textured and dry so it attracts more dust. Asides from this, acrylic paint can’t be wiped with solvents. To clean it with a solvent, you’ll need to thin the solvent first. Also, the solvent must be water-based.
Which Finish Do You Need?
Here are a few factors to consider when choosing between these two finishes:
- Budget – If you have a limited budget, use acrylic varnish as it costs less.
- Finish – if you want a colorful finish, use acrylic. If you have a clear glossy and durable finish, use polyurethane.
- Protection – If you want surface protection, use polyurethane as it is moisture-resistant.
- Surface – For outdoor surfaces, use oil-based or exterior polyurethane. For low-traffic indoor surfaces, use acrylic paint.
- Cleaning – Polyurethane doesn’t attach much dust or stains and is easier to clean its glossy finish.
- Durability – If you need a finish that will last long, polyurethane is your pick. Since the finish is stronger, it can last about 10 years if properly applied and maintained.
In summary, acrylic is a water-based paint used to give color to porous surfaces, while polyurethane is a transparent sealant used to protect high-traffic surfaces.
To get the best of two worlds, you can apply the paint and then seal it. Or, mix water-based poly with acrylic to get a durable and colorful finish.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,