Two of the most common varnish paints are polyurethane and acrylic. So, what’s the difference between both finishes?
The main difference between polyurethane and acrylic paint is that acrylic paint is water-based while polyurethane is usually oil-based. Acrylic varnish due to its water-based nature retains its clear film for years. Oil-based polyurethane however starts to develop a yellowish tint in the clear coat after a few months. This is due to the presence of oil deposits in the clear coat.
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, polyurethane is usually stronger and more resistant to moisture than acrylic paint.
What is Polyurethane?
Polyurethane, also known as polyurethane varnish, is a clear synthetic resin. Polyurethane 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.
Polyurethane when dry forms a thick plastic film that protects the surface underneath. The word “urethane” refers to a strong and flexible plastic-like material. Being plastic, the finish of polyurethane 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 polyurethane wasn’t mixed before application.
What is Polyurethane Used For?
- Polyurethane is used to protect wood.
- Polyurethane prevents moisture damage on wood and wood stains.
- You can put polyurethane over other sealants.
- You can use polyurethane to protect hardwood flooring.
- Polyurethane is common in high-traffic areas like tabletops and countertops.
What is Acrylic Paint?
Acrylic paint or acrylic varnish is a water-based clear coat used over indoor furniture. Being a water-based finish, acrylic paint dries within 24 hours. Acrylic paint is beginner-friendly as mistakes don’t affect the paint much. Plus, the paint is much easier to repair than other types of clear finishes.
During the first few hours after application, acrylic 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, acrylic paint can give color to wood, which most clear coats can’t. That’s because acrylic paint can be tinted with water-based colorants and other acrylic paints to give the finish color.
What is Acrylic Paint Used For?
- Acrylic paint is used to cover water-based stains.
- Acrylic paint is used over indoor wood.
- The finish gives color to wood grain.
- Acrylic paint protects wood from blemishes and scars.
So is polyurethane better than acrylic paint? Let’s find out by comparing both paints.
Polyurethane Varnish vs Acrylic Paint
To find out the superior paint, we’ll use the features of a standard wood finish and see how both finishes compare.
Here is a table that shows the major differences between polyurethane and acrylic paint:
|Polyurethane Varnish||Acrylic Paint|
|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 while acrylic paint is water-based or dissolved in water. Polyurethane also contains more chemical compounds than acrylic paint.
While most acrylic paints are made from urethane and water, polyurethane contains extra solvents and resins. Polyurethane also contains large amounts of urethane plastic.
Verdict: Polyurethane has a more complex formula than acrylic paint.
The Dry Time
Polyurethane takes longer to dry than acrylic paint. This is because of the formula and base of polyurethane. The solvent (oil) on polyurethane takes longer to evaporate than the solvent (water) on acrylic paint.
Also, polyurethane only forms 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.
Verdict: Acrylic paint dries faster than polyurethane.
Polyurethane offers better moisture resistance than acrylic paint. Since polyurethane dries harder than acrylic paint, it’s difficult for water to penetrate the polyurethane coating. Also, when dry, polyurethane 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 as polyurethane. Since acrylic paint is dissolved in water, it will start to show signs of damage if exposed to high moisture content for long periods.
Exterior polyurethane can withstand rainfall. But, if acrylic paint is exposed to rainfall, the finish will get damaged.
Polyurethane and acrylic finishes offer good protection to wood, but polyurethane protects wood better. This is because a polyurethane finish is harder than an acrylic finish.
Polyurethane finish can withstand dents, and wood damage, and offers heat and moisture resistant features. Exterior polyurethane also offers UV resistance to wood. While acrylic paint doesn’t.
The Type of Finish
Polyurethane offers a slick and smooth glossy sheen when dry. The sheen makes the wood reflective as the glossy top coat on the wood reflects light.
The acrylic finish is not glossy or reflective. Acrylic paint offers a dry, textured, and sometimes colorful finish. Since acrylic paint is water-based, the finish can be thinned with water-based colors to make the finish colorful and attractive.
So, acrylic paint offers more color and beauty, while polyurethane finish is glossy and hard. But, you can seal acrylic paint to make it more durable.
Verdict: Acrylic paint has a more attractive finish than polyurethane. Polyurethane offers a glossy finish.
Purpose and Usage
Because of the hard and moisture-resistant finish, polyurethane is used over high-traffic surfaces. Polyurethane can be used over floors and surfaces such as patios, walkways, tabletops, desks, stairs, etc. Exterior polyurethane can be used outdoors because of the UV resistance formula.
Acrylic paint is used for low-traffic indoor surfaces such as drawers, cabinets, chairs, indoor furniture, etc. Acrylic paint will make indoor furniture appear attractive. You shouldn’t use acrylic paint outdoors because the finish isn’t strong enough to last.
Verdict: Polyurethane can be used outdoors and on high-traffic areas like stairs. Acrylic should be used indoors and on moderately used surfaces like furniture.
Cleaning and Maintenance
It’s easier to clean and maintain polyurethane. That’s because polyurethane rarely attracts dust or filth since the finish is hard and glossy. Also, polyurethane can be wiped with water and solvents to remove stains and grease on the finish.
You’ll be doing more cleaning with acrylic paint. Acrylic paint is textured and dry so it attracts more dust than polyurethane. Asides from this, acrylic paint can’t be wiped with solvents. To clean acrylic paint 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 polyurethane varnish and acrylic paint:
The Price Tag
You should go for a finish that you can afford. Though there exist size variations between polyurethane and acrylic products, polyurethane tends to be costlier than acrylic paint. You can get acrylic varnish for $20 while polyurethane varnish will cost about $30.
No one wants an ugly finish. So you should remember that acrylic paint offers more beauty and color to wood. Polyurethane finish is clear and boring.
If you want to protect the wood, polyurethane is your pick. Polyurethane offers better overall wood protection than varnish. Also, polyurethane can withstand pencil marks, dents, and gouges so the wood will be well protected from any damage.
Indoor or Outdoor Use?
Polyurethane is better for outdoor use while acrylic paint will thrive indoors.
Cleaning and Maintenance
Since polyurethane doesn’t attract dust and oils, you wouldn’t be doing much cleaning or maintenance. So polyurethane is more user-friendly.
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. Acrylic paints will last about 5 years at best.
Overall, polyurethane varnish and acrylic paint are good finishes on wood. Ultimately, the choice you make depends on your taste and the type of wood. Remember, polyurethane is suited to outdoor use and offers superior wood protection.
Acrylic paint offers inferior wood protection but a better finish. Also, polyurethane can be used indoors and outdoors while acrylic paint is suited to indoor use.