Two of the most common varnish paints are polyurethane varnish and acrylic varnish. But what’s the difference between both finishes?
The main difference between polyurethane and acrylic paint is 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 quickly. On average, acrylic paint dries fully 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.
When polyurethane is used on wood, the polyurethane bites into the wood giving the paint good adhesion. But adhesion is not what polyurethane is known for.
Polyurethane is popular because of the thick plastic-like film that the finish gives. The word “urethane” refers to a strong and flexible plastic-like material. Being plastic, the finish of polyurethane is clear and transparent.
However, polyurethane is known to develop a yellowish or amber-like tint after a few months. This is common with oil-based polyurethane. Water-based polyurethane rarely develops any yellow tint. But, the clear coat can also turn cloudy especially if the polyurethane wasn’t mixed before application. Next, let’s figure out what polyurethane is used for.
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 on high-traffic areas like tabletops and countertops.
What is Acrylic Paint?
Acrylic paint or acrylic varnish is a water-based clear coat commonly used over indoor furniture. Being a water-based finish, acrylic paint is known to dry quickly and completely in less than 24 hours. This finish is okay for beginners as mistakes don’t affect the paint much. Also, acrylic paint is much easier to repair than other types of clear finishes.
Acrylic clear coat when applied doesn’t appear clear. During the first few hours after application, acrylic paint appears cloudy and whitish. But this whitish film becomes a clear coat after it has cured. The water-based nature of acrylic paint means the paint is lighter than most clear coats. This also means it can be thinned easily with water.
The best perk to acrylic paint is that it’s one of the few coats that can give color to wood. Being a water-based coat, acrylic paint can be tinted with water-based colorants and even 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 complex paint formula means that it will take longer for polyurethane to dry.
You should know that polyurethane only forms after a chemical reaction between polyols and – isocyanates compounds. Since acrylic paint has a simple formula, it will dry quicker.
Also, acrylic paint is water-based and water-based finishes generally dry fully in less than 24 hours. Polyurethane can take up to 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 to the wood underneath. Also, polyurethane produces a glossy sheen when dry. This sheen repels moisture so it’s even more difficult for water to pass through.
Acrylic paint on the other hand 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 even withstand rainfall. 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.
As such, the polyurethane finish will withstand dents and potential wood damage better than acrylic paint. Also, polyurethane offers heat resistance and superior moisture. This also protects the wood from heat and water damage. Some types of polyurethane like exterior polyurethane offer UV resistance to wood.
The Type of Finish
Polyurethane offers a glossy sheen when dry. This sheen is usually slick and smooth. The sheen also makes the wood reflective as the glossy top coat on the wood reflects light. Acrylic finish on the other hand 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.
Mixing water-based color with polyurethane is harder and can only be done with water-based polyurethane. So acrylic paint offers more color and beauty while polyurethane finish is glossy and hard. You can even seal acrylic paint with another coat.
Verdict: Acrylic paint has a more attractive finish than polyurethane. Polyurethane offers a glossy finish.
Purpose and Usage
The hard and moisture-resistant finish of polyurethane means that polyurethane can be used over high-traffic areas. Also, polyurethane can be used on floors and heavily used surfaces like patios, walkways, tabletops, desks, stairs, and the likes. Exterior polyurethane can also be used outdoor because it offers UV resistance.
Acrylic paint on the other hand is suited to indoor use. Acrylic paint shouldn’t be used on exterior wood because the finish is not strong enough to last on such wood. Acrylic paint is suited to drawers, cabinets, chairs, and indoor furniture. Since these surfaces wouldn’t see much friction, the acrylic paint will last. Also, the acrylic finish is fine enough to make furniture and indoor wood appear attractive.
Verdict: Polyurethane can be used outdoors and on high-traffic areas like stairs. Varnish should be used indoors and on moderately used surfaces like furniture.
Polyurethane offers better heat resistance than acrylic paint. This is because polyurethane has flexible qualities. The presence of urethane plastic in the paint means that polyurethane can contract and expand based on temperature changes. When it gets too hot, polyurethane will expand so the coat can cope better without coming off.
Acrylic paint is not heat resistant. Since the finish has no oils, it is less resistant to heat. If you use acrylic paint close to a heat source like the fireplace, the paint will turn brown.
Cleaning and Maintenance
It’s easier to clean and maintain polyurethane. The reason for this is that 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.
Acrylic paint since the paint is textured and dry attracts more dust than polyurethane. So you’ll be doing more cleaning with acrylic paint. 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.
Do You Need Polyurethane or Acrylic Paint?
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.