Have you noticed that the color on your painted furniture is fading, flaking off, or becoming dirty and are seeking a potential fix to stop the damage from worsening and spreading? So, can one put polyurethane over paint? Yes, you can apply polyurethane over paint. This article will discuss several cases under which you can apply poly over paint and things to avoid during the process.
Let’s get started!
What Is Polyurethane?
Polyurethane is a petroleum-based liquid, the same compound used to make plastic items, that we utilize to coat and adhere to wood surfaces to add longevity. Polyurethanes are available in water- and oil-based varieties, each having a distinct function. Nevertheless, you can employ both to provide a surface with an additional layer of protection.
Oil-based polyurethane takes longer to dry and solidify, has a slight odor upon drying, and creates a yellow or amber hue when applied to paint. On the other hand, water-based poly does not produce any amber coloration and dries rapidly. Although polyurethane is not very delicate, it can still be cracked or chipped if exceptionally high temperatures or strong chemicals are employed.
Image credit: minwax.com
Oil-based polyurethane is more resilient and resistant to harsh environments than its water-based counterpart. Ethylene is the most popular substance used to make polyurethane; however, its high molecular weight can only be utilized in specific ratios. Other frequently used polyurethane components (BMA) are Propylene, Butyl Methacrylate, and Cement Si.
When Is It Okay to Apply Polyurethane Over Paint?
Applying a polyurethane finish over the paint is possible once it has dried. When putting polyurethane over paint, this is the only aspect to consider. But how long should the drying process take?
Although the curing process for paint typically takes 24 hours, the process can be sped up or slowed down by weather and other circumstances. Since there are procedures you must take before applying the polyurethane finish, you must wait until the paint has entirely dried.
Before applying the polyurethane, you must clean and rub it to eliminate impurities from the painted surface. Failure to do so will result in improper poly adhesion. The cleaning procedure will obliterate the painted surface if it is still wet and penetrate the wood, which might damage it.
Given that the surface dries more quickly, it is crucial to allow wood adequate time to cure—ideally 72 hours. The sanding will uncover the wet paint below if the painted surface is dry but the lower layers are not, resulting in the same issue. The wood would then need to be repainted, and you would need to wait a few more days before adding the polyurethane finish.
Image credit: nhancefranchise.com
When applying polyurethane to paint, there is also the possibility of discoloration. If the paint is thoroughly dried, this is less likely to occur. If not, you risk discoloration and it losing its clear coat status since the polyurethane can mix with the paint.
How to Put Polyurethane Over Paint
1. Get the Surface Ready
Make sure your painted surface is spotless before using any form of polyurethane.
2. Sand the Surface
After thoroughly cleaning every surface with a damp rag or tack cloth, lightly sand it down before sealing the paint finishes with polyurethane. This extra step will give your wall surfaces an even and glossy finish.
Read more on whether you can paint woodwork without sanding.
3. Add a Foundation Coat
On top of the paint, apply a single, thin first coat of pure polyurethane. Before applying a second coat, leave the first coat for an hour to dry and remove any excess paint. If you use too much product, the material may dry with cracks and bubbles. Instead, apply it thinly and evenly over painted surfaces with a natural-bristle brush instead of a foam brush.
4. Apply Finishing Coats
To completely cover all wall surfaces, the second coat should be thicker than the first. Depending on how many coats you apply, give each one at least an hour to thoroughly dry before applying another.
Image credit: thisoldhouse.com
5. Apply a Second Polyurethane Coat
As the last stage, add a second layer of finishing material for a more robust defense against moisture and grit. If you want to paint over the polyurethane-coated surfaces of your walls, this method can strengthen the bond between the paint and the surface.
How to Use Polyurethane to Achieve the Smoothest and Most Attractive Outcomes
Sanding between applications is excellent, even if it is only sometimes 100% essential for adherence. Between layers, carefully sanding the surface will eliminate runs and brush marks, remove small dust particles that could have adhered to the wet surface, and slightly roughen the surface so that the subsequent coating will adhere.
320-grit sandpaper is the best grit to use when sanding in between layers. It will give the surface a thorough sanding without leaving the finish with significant scratches that finer grits may readily go. Apply the last layer as smoothly as possible for a flat, durable finish.
How to Use Polyurethane to Get a Surface Look Like Glass
When the final coat has had time to cure, sand it with progressively finer grit paper. Be careful not to rub through the finish on the edges as you work your way up the grit scale, starting at 600. You might not be able to obtain high-quality sandpaper of this kind at a hardware store, but automotive stores have it.
Remember that you should regularly examine the sandpaper’s surface to ensure there is no sanding dust or buildup that might cause it to harm your finish. You should only sand a little if your piece has intricate work and isn’t flat, so you don’t remove the finish.
If you want a high-quality mirror finish and a smooth surface without dips or visible wood pores, continue by buffing with paste wax or auto polish using a non-abrasive foam pad or microfiber cloth.
Image credit: cnet.com
Can You Put Polyurethane Over Several Types of Paint?
Now that we have covered the fundamentals, we can move to the characteristics of how poly interacts with various types of paint. The careful application will result in the perfect shine, increased durability, and a longer interval between coats of paint.
1. Polyurethane Over Acrylic Paint
Acrylic paint and poly go over one other rather nicely. In most cases, we advise applying water-based polyurethane over dry (but fully cured) acrylic paint. It is highly received and has no adverse effects on how acrylic paints dry.
It is okay to apply oil-based poly if the acrylic paint coat is more than 30 days old, especially if it is necessary to warm up the hue a little and gently roughen the surface for adherence.
2. Polyurethane Over Latex Paint
In terms of composition, latex paint is water-based and identical to acrylic paint. Applying polyurethane over a dry coat of latex paint should go without issues, mainly since such products are often thinner and tend to dry faster.
Give the latex paint layer some time to dry, at least in its outer layer, if you only have or desire oil-based poly.
3. Polyurethane Over Chalk Paint
Since chalk paint coats are delicate by nature, they need some protective covering when you use them permanently. Although there are specific waxes for chalk paint, water-based polyurethane will work. Without a topcoat, the surface would develop deep scratches that need to be protected with a few thin coatings.
Oil-based polyurethane is also okay, but you must thin it with some paint thinner to give it the necessary viscosity to cover chalk paint smoothly.
4. Polyurethane Over Enamel Paint
The use of poly over enamel paint for protection usually serves little purpose because enamel paint is often long-lasting. To get the shine you want, you can go for it.
Image credit: homedepot.com
We advise sanding with 240 grit or higher for good adhesion if you apply polyurethane over enamel paint. Oil polyurethane and water-based poly will apply smoothly over a dry coat of high gloss paint when it comes to bonding when applied neatly and delicately.
5. Polyurethane Over Paint in Spray Form
In terms of its composition, spray paint is not a distinct form of paint. It is a suitable type of packing. You may use spray paint with acrylic paint and some oil-based paints. As long as you follow the methods’ basic instructions, applying polyurethane varnish over oil-based paint on various items should not present any issues.
It is a good idea to apply a couple of coats of polyurethane as protection if you are spray-painting indoor or outdoor furniture.
Frequently Asked Questions
a) Can you apply polyurethane over high gloss paint?
You can apply polyurethane to high gloss paints, but you should know that it adheres less effectively to glossy surfaces than flat, matte, or satin surfaces. Remember that flat, matte, satin, and chalky finishes are less resilient than semi-gloss and gloss. This may be taken into account while selecting paints and finishes.
b) Can you use polyurethane over white paint?
Yes, you may apply polyurethane over most paint types, including transparent and white paint.
However, it is crucial to remember that you should always use a single thin layer rather than a single thick coat when dealing with this material!
c) Can you apply polyurethane over shellac?
Since shellac covers everything, you should not apply poly over shellac. Shellac-finished woodworks occasionally buff out white markings when splashed with water, and the solution is to remove the shellac and refinish the wood with poly.
Image credit: youtube.com
d) Can you paint acrylic enamel over urethane primer?
Yes, however, you must first sand the priming before painting. Acrylic enamel is an elastic paint-like substance that can conform to uneven surfaces like primers.
e) Can you use polyurethane over the painted floor?
Yes, you can apply polyurethane over the painted floor. To ensure that it is protected in a high-traffic location, you should use at least three coats of polyurethane. Allow adequate time for drying between each layer.
Featured Image Credit: thisoldhouse.com