Yes, you can surely apply polyurethane over acrylic paint. Polyurethane will help you preserve your art for longer and apply a glossy finish to the surface.
But you should remember a few things before diving straight into it.
Avoid oil-based polyurethane and use water-based ones, and clean the surface well before applying the coating.
As long as you follow the steps we will discuss below and keep the precautions in mind, you are good to go.
Can You Use Polyurethane Over Any Kind of Paint?
Yes, you can use polyurethane over any kind of paint including acrylic, latex, enamel, chalk, and other types of paints. Sometimes polyurethane might cause yellowing or fading when applied to oil-based paints.
However, oil paintings tend to naturally develop a yellowish shade after some years. Therefore, using polyurethane shouldn’t be an issue.
Remember, the condition of the paint will decide whether the polyurethane coat will stick to the painted surface or it will ruin the paint. You must let the painted surface dry and cure for a week. This way, the paint won’t flake or mix with the polyurethane layer.
Also, sand the surface before applying polyurethane to smoothen it and remove any bubbles, dirt, or grease that might be sticking to the painted surface.
Which Types of Polyurethane Should I Put Over Acrylic Paint?
If you want to use polyurethane to seal acrylic paint, you have two main options: Oil-based polyurethane and Acrylic-based polyurethane. Although you can use both types, water-based ones are definitely preferable. Here’s why:
- Oil-Based Polyurethane
You can use oil-based polyurethane to achieve a rich, smooth, and golden glow. This type of polyurethane lasts longer and feels softer than water-based ones.
However, the main issue is that oil-based polyurethane is flammable and contains toxic chemicals.
Moreover, it takes a few hours longer to dry (drying time 3 to 6 hours) than water-based polyurethane. Over time, it will develop a yellowish hue which might change the shades of your acrylic painting.
- Water-Based Polyurethane
This is the most popular option for acrylic paintings as water-based polyurethane doesn’t have the issues as oil-based polyurethane. It provides the same high-quality protective coating as any oil-based polyurethane.
Although the coat is a bit too hard, it’s highly durable and not prone to yellowing over time. Also, water-based polyurethane contains 50% fewer VOCs than oil-based polyurethane. Which means it’s less toxic to your health and the environment.
Finally, water-based polyurethane is faster drying taking only 2 hours to dry. So, this is our final recommendation if you want to seal any acrylic-painted surface.
Benefits of Using Polyurethane Over Acrylic Paint
Coating art pieces with polyurethane is a common technique many pro artists use to preserve their art for longer. Moreover, there are many other benefits of using polyurethane on paint.
Durability
No matter how impressive your brushstrokes, color composition, and designs on the painting are, like all things, they will fade. It will go through scratching, chipping, and unspeakable wear and tear.
Unless you protect it with a coat of polyurethane, of course! Polyurethane will work like a shield against dirt, chemicals, moisture, abrasion, temperature, and fungi.
Water Resistance
Polyurethane is essentially liquid plastic which, when applied to paint, forms a protective layer against the surface after drying.
If you plan to hang your painting near somewhere where there is a risk of water damage (maybe a fountain), then applying polyurethane is definitely something you should consider.
UV Resistant
Ultraviolet rays can cause all types of damage to acrylics. It can change the artwork at a molecular level if not appropriately protected. UV light can cause the colors to fade after a certain period of time, which you definitely do not want.
Fortunately, water-based polyurethane can completely nullify the damaging effects of UV rays on acrylic paint.
So, if you plan to hang your masterpiece on the outside, applying water-based polyurethane over acrylic paint is a must-go!
Easy to Clean
Polyurethane coating gives your paint an extremely smooth finish. If you need to regularly wipe your painting off dirt and grime, polyurethane will make your job simple and easy.
Gives an Aesthetic Finish to Your Painting
Polyurethane gives your painting a glossy look, making it look more professional and polished. Sometimes, that glossy finish can be exactly the thing that is needed to make your work stand out.
To spruce up your aesthetic painting, you can wood burn over acrylic paint!
Summary
Polyurethane makes your acrylic art more resistant to damage, easier to clean, and more pleasing to look at.
Things You Will Need for Putting Polyurethane over Acrylic
It is good to keep all your tools nearby while applying polyurethane on acrylic paint so that you don’t have to interrupt your workflow in the middle of the process.
Here are all the tools you will need −
- Polyurethane
- Clean, dry clothes or rags
- Sandpaper
- Drop cloths
- Paintbrush or roller
- Masking tape
You’ll need the cloth to clean up the surface and the tools. If the surface is uneven and has bumps, then use sandpaper (preferably a fine-grit one) to make the surface smoother.
Depending on the type of polyurethane you are using and your preferred application method, you may need a paintbrush or roller to apply the polyurethane.
Use rollers to hold more paint and cover a large area. Otherwise, go with your paintbrush to apply polyurethane on smaller areas with more precision.
Drop cloths are to protect the floor from drips or spills.
If there are any particular areas you don’t want the polyurethane applied to, then use masking tape to cover them.
How to Use Polyurethane Over Acrylic Paint? − Step-by-Step Guide
If you ever plan on putting polyurethane coating over your artwork to make it more durable and glossier, you’ll need a detailed guide. So, here in this section, we’ll walk you through the process with every piece of information you might need.
Step 1 − If the paint is recent, then wait for it to dry. Acrylic is a water-based paint, so it dries pretty quickly. Wait for around 2 hours at least and ensure no part of the painting is wet before following the next step.
Step 2 − Use fine-grit sandpaper (100-120 grit) to sand the surface and fix any uneven bulges or lumps. Sanding helps create a smooth finish on the canvas, and paint sticks much easier to it.
Step 3 − Wipe the surface clean with a clean dried cloth after you have sanded. This will remove any dust particles or chunks that may remain after the sanding process from interfering with the polyurethane.
Step 4 − Read the instructions on your polyurethane package. See if it’s a roll-on polyurethane or a spray polyurethane. If you want to coat a specific area, use roll-on polyurethane. Spray polyurethane are a better choice for beginners as it’s easier to apply on a large area.
Depending on the polyurethane type, use a roller, paintbrush, or spray. Apply the polyurethane in medium-thin coatings.
Step 5 − Polyurethane can take 3 to 6 hours to dry fully. But you should still wait overnight to apply additional layers of polyurethane.
Step 6 − Sand lightly between coats of polyurethane to ensure a smoother finish. Only two layers of polyurethane are enough to protect the paint. However, you can apply 3 to 4 thin layers for longer-lasting protection.
Step 7 − Once the final coat has dried, use a clean, dried cloth to remove any dust or debris. And your job is done! Polyurethane can take about 1-2 days to dry off fully, so be careful handling the surface before that time has passed.
Summary
Sand the dried acrylic paint first to smooth it out. Make sure it’s clean of dust and debris. Use water-based polyurethane and sand between coats.
Make sure each layer dries up properly before applying the next one. Finally, use a clean and dry cloth to dust off any residue or debris left.
Once you’re done with the process, give the surface a day or two to dry properly. Otherwise, your artwork will get ruined.
How Soon Should You Apply Polyurethane over Acrylic Paint?
It depends on the type of acrylic paint and polyurethane you’re using. You must wait until the paint fully cures. Acrylic paint can take only a day or two to cure.
Artists’ grade acrylics are thicker than students’ grade ones and take longer to dry and cure.
Also, the number of layers in the painting will also alter the drying time. So, it’s best if you can let the paint cure for 72 hours. Now, if you’re using oil-based urethane, wait for 4 to 6 hours to let each layer of polyurethane dry.
For water-based ones, 2 hours should be enough.
Why Is the Polyurethane Not Drying?
If your polyurethane coat is taking too long to dry, something must have gone wrong. Below are the reasons why polyurethane might not dry and some easy fixes. Let’s take a look.
Not Giving Enough Time Between Layers
Polyurethane coats take a long time to dry, especially oil-based ones. If you apply a new layer of polyurethane while the previous one is still wet, the final coat will take a long time to dry.
The Fix
On average, you should wait at least four hours before you apply a new layer of polyurethane. This way, the previous layer will get enough time to dry and the final coat won’t take any longer.
Dirt and Grease on the Surface
As the painted surface is exposed to an open environment, dirt, grease, dust, and other filth can easily stick to the surface. The same thing can happen if you’re applying multiple polyurethane layers as each layer takes a long time to dry.
If the surface has dirt or grease, polyurethane won’t sit well or get lumpy. Either way, the polyurethane coat will remain sticky for a long time.
The Fix:
Before you apply the first coat of polyurethane, sand the painted surface first to remove all types of dirt and grease. Sand each of the polyurethane layers as well once it’s dried.
Low Temperature
Leaving the polyurethane coat to dry in a particularly cold area can be the reason why it’s not drying. Polyurethane dries by evaporation and low temperature makes the process extremely slow. Therefore, the coat doesn’t dry even after a day or two.
The Fix:
Store the coated painting in a hot area if you can. Turn on the room heater to facilitate the drying process. You can also use your hair dryer or a heat lamp to make polyurethane dry faster.
Insufficient Air
Sufficient air circulation is a must for drying and curing the polyurethane coat. Airflow can also remove excess moisture from the area. If you keep the paint in a closed room where the air is trapped, it will take forever for the polyurethane to dry.
Be aware of including acrylic paint with food-grade applications. Although polyurethane is food-safe, acrylic paint is not food-safe. So, take enough precautions while dealing with the paints.
The Fix:
Ensure proper air circulation in the area where you’re putting the paint for drying. Open the windows and turn on the exhaust fan if there’s any. You can keep the painted surface outdoors for faster results.
Thick Coats
As you can guess, thicker layers mean more polyurethane which takes more time to dry. So, applying thick coats of polyurethane will keep the surface sticky for longer.
The Fix:
Instead of applying one or two thick layers, use multiple thin layers to get the perfect coat without making the surface slow drying.
Alternatives to Polyurethane for Using Over Acrylic Paint
The purpose of using polyurethane is to protect acrylic paint from fading due to environmental damage. Apart from polyurethane, a few other products can be used for the same purpose.
Here are some common sealants used to protect acrylic paint-
Polycrylic Protective Finish
Minwax has developed a special poly-acrylic sealant that can be used to protect acrylic paint for a long time. It provides a clear coating that doesn’t develop a yellow hue over time.
Although this sealant is less toxic than polyurethane, it doesn’t last as long as polyurethane. However, it’s available in different finishes such as matte, gloss, semi-gloss, etc.
In case, you’re not a beginner-level painter but work with
Varnish
Using varnish is a traditional way of sealing acrylic paint. You can pick either resin varnish or polymer varnish.
Resin varnishes are glossy, strong, and long-lasting. They create a clear coat to protect the acrylic paint.
Polymer varnishes offer a matte or satin finish that is also highly durable. It’s less toxic than resin varnish and not prone to yellowing. You can choose resin varnish for a glossy coat and polymer varnish for a matte finish.
Clear Coat Aerosol Sealant
As it comes in a spray form, this sealant is easier to apply. It provides a clear, smudge-proof, and water-resistant finish to protect the acrylic paint.
You can use this clear coat aerosol sealant on all types of painted surfaces including canvas, ceramic, wood, metal, and plastic. The product is non-toxic, non-yellowing, and permanent on acrylic paint.
Frequently Asked Questions
It depends on which surface you’re using the paint on. For most hard surfaces such as wood, plastic, metal, and even canvas, you can use a sealer to protect the paint from damaging factors (UV rays, moisture, dirt, intense light, etc.).
To make acrylic paint permanent on fabrics, mix a fabric medium with the paint and apply high heat after the paint dries.
Yes, you can apply a coat of varnish or polyurethane to make acrylic paint waterproof. Both these products create a hard protective layer on the paint that prevents water from reaching the paint.
Adding a gloss medium to acrylic paint will make it look glossy. You can use a gloss or semi-gloss clear acrylic sealant as well to create a glazing protective coat on the painted surface.
Bottom Line
So, can you put polyurethane over acrylic paint?
Well, YES! As long as you abide by all the precautions. Polyurethane looks good on your art; it provides durability and protection from damage.
Choose the right polyurethane to fit your preference and apply sanding in between.
We hope this article provided you with a comprehensive understanding of how polyurethane works and how to apply it properly.