Let me get this straight – you want to apply a finish on another finish? I’m just messing with you! Every now and then, you find that after you have painted a wooden surface, you’re not pleased with the result.
It looks great, but it just feels like something is missing. If your solution is to apply polyurethane over paint, then I salute your ingenuity.
Poly can create a unique look on any type of paint. The only thing that can go wrong is not knowing how long for paint to dry before polyurethane.
Can You Put Polyurethane Over Paint?
Yes, you can put polyurethane over paint. As long as the paint is fully cured and clean, you can apply both water-based and oil-based polyurethane over any type of paint. However, you must be cautious of discoloration, especially from oil-based polyurethane.
Now that you know it’s possible to apply poly over painted surfaces, let’s find out how long you should wait for the paint to dry before applying polyurethane finish.
How Long for Paint to Dry Before Polyurethane?
Allow the paint at least 24 to 72 hours to dry before polyurethane, depending on the type of paint you are using. If you are unsure if the paint has fully cured, wait an extra day or two to be safe.
When Can I Apply Polyurethane Over Paint?
Once the paint has cured, you can apply polyurethane finish over the paint. This is the only factor you need to consider before you apply polyurethane over paint.
How long should you wait to put polyurethane over paint?
On average, it takes paint 24 hours to cure, but different weather conditions and other factors can slow down this process.
You must wait until the paint is fully cured because of the steps you need to take before applying the polyurethane finish.
Before applying the polyurethane, you must clean and abrade the painted surface to remove impurities. If you don’t, the poly won’t adhere properly.
If the painted surface is still wet, the cleaning process will obliterate it and get into the wood, which can spoil it. It is important to give the wood enough time to cure – ideally 72 hours – because the surface dries quicker.
If the painted surface is dry, but the lower layers aren’t, the sanding process will reveal the wet paint underneath, and we’ll have the same problem.
You would then need to repaint the wood and wait for another few days before applying the polyurethane finish.
There is also the risk of discoloring when you apply polyurethane to paint. This is less likely to happen if the paint has fully cured. Otherwise, you risk discoloration, and the polyurethane could mix with the paint, and it will no longer be a clear coat.
Can You Put Polyurethane Over High Gloss Paint?
Yes, you can put polyurethane over high gloss paint once the surface is dry and fully cured. As earlier mentioned, you can polyurethane over any paints, including semi-gloss paints, high gloss, chalk paint, latex paint, water and oil-based paint, or even acrylic paint to attain a durable finish. Ensure you prepare the painted surface and apply the polyurethane finish correctly.
What Type of Polyurethane Can you Apply Over Paint and Their Drying Time?
You can apply any type of polyurethane over paint. Polyurethane is a clear coat finish, so it will still show the beauty of the paint beneath the scratch-resistant and waterproof covering.
Oil or Water Based: Types of Polyurethane & Drying Times
Both oil and water-based poly do the same thing. The only difference is how they look and how long the polyurethane will take to dry.
As mentioned previously, oil polyurethane has an amber tint, making it perfect for applying on raw or stained wood. It gives it a distinct, darker look that will preserve the original color of the wood.
Oil-based polyurethane dries to the touch in 6 to 24 hours, depending on the type of product you use. Fast-drying polyurethane takes 6 hours, while regular poly takes at least 12 hours.
After one week of application, your woodwork is ready for light use. It then takes another three weeks before the wood fully cures.
Water-based polyurethane over paint
Water-based polyurethane is best for applying over wood because it remains clear and dries quickly. In just two hours, the average fast-drying water-based finish is ready for a second coat.
In 24 hours, it is ready for light use and can cure in as little as 3 days. However, like with paint, many factors can slow the drying time. Therefore, you must wait at least 21 days for the water-based to cure fully.
How to Apply Polyurethane Over Paint
Given you have already done the hard work of making the wood usable, you won’t need to spend as much time applying polyurethane finish.
Tools You’ll Need
- Detergent or trisodium phosphate (TSP)
- Water-based or oil-based polyurethane
- Tack cloth
- Vacuum cleaner
- Lint-free cloth
- 120-grit sandpaper for deep scratches
- 220-grit sandpaper
- Applicator – paint brush, spray, pad, or roller
- Rubber gloves
Steps to Applying Polyurethane Over Paint
Step 1: Clean the Surface
Polyurethane does not adhere properly to greasy surfaces, so you must clean the painted surface thoroughly with detergent or trisodium phosphate (TSP). While TSP is better known as a food additive, the concentrated dose is a powerful cleaning product.
Use TSP for old paint and detergent for a recent application. Wear goggles and rubber gloves when using TSP to protect yourself.
Step 2: Sand the Surface
Use 120-grit sandpaper to remove any deep scratches on the surface of the wood. Sand to flatten the sheen in the paint.
Use a palm sander if you can’t get a flat smooth surface manually with 120-grit sandpaper.
Step 3: Tack the Wood
Clean the sanding residue using a vacuum cleaner or a tack cloth. Make sure there is no trace of dust left, or it will ruin your polyurethane application.
You can dip a lint-free cloth in water and use it to clean the surface. This method gets rid of dust better, but you must let it dry afterward before the next step.
Step 4: Apply the First Coat of Polyurethane
Apply a thin coat of any polyurethane you want, whether oil-based or water-based, making sure to follow the grain. You can use any tool to apply the first coat – a brush, roller, pad, or spray.
Once you are done, leave the polyurethane finish to dry.
Step 5: Sand After Drying
Once the polyurethane varnish is dry, use 220 grit sandpaper to smoothen the surface. Sanding between polyurethane coats will help eliminate dust nibs, brush marks, or other imperfections such as deep scratches.
Step 6: Clean the Painted Surface Again
Follow the same routine as in step 3 to eradicate the sanding residue and small dust particles.
Step 7: Apply a Second Coat of Polyurethane
Generally, the first coat isn’t always enough. Apply another thin coat of polyurethane, using the same process as before. Wait for it to dry, then repeat steps 5 to 7 until you achieve the desired level of smoothness. Applying two coats or more is advisable, especially for water-based poly.
Can You Put Polyurethane Over Acrylic Paint?
Yes, you can apply both oil-based and water-based polyurethane over the paint. The polyurethane will protect the surface of the paint while also making it look more appealing and durable. As long as you have properly prepared the surface of the acrylic paint, the polyurethane won’t ruin it.
What Is Polyurethane?
Polyurethane is a petroleum-based liquid from plastic products used for coating and adhesion to add durability to your woodworks. They come in two forms; water-based and oil-based.
Each one of these forms has its particular purpose. However, they are used for the same purpose: to provide an extra layer of protection to a surface.
Oil-based polyurethane leaves off amber coloring when applied on paint, takes a longer time to dry and harden, and gives a slight odor when dry. On the other hand, water-based poly dries quickly and doesn’t give any amber coloring.
The layer of polyurethane provides additional toughness against abrasion and scratches and doesn’t absorb water. It dries clear and helps to prevent heat damage to your surface.
While polyurethane isn’t particularly fragile, it can still break or chip if extreme temperatures or harsh chemicals are used.
The most common material used to create polyurethanes is Ethylene, but because of its molecular weight, it can only be used in certain mixtures. Other commonly used polyurethane ingredients are Cement Si, Propylene, and Butyl Methacrylate (BMA).
Oil-based polyurethane is more durable than water-based polyurethane and can withstand extreme conditions. For other comparisons of the two, read this article.
What Is Acrylic Paint?
It’s a fast-drying paint made of pigment suspended in acrylic polymer emulsion and silicon oils, metal soaps, plasticizers, stabilizers, or defoamers. Unlike most materials, acrylic paint dries quickly and doesn’t require a long drying time.
This paint’s physical and optical properties make it ideal for use on a wide range of painted surfaces.
However, if you want to use this type of paint on your painted surfaces, you must use high-quality oil-based paint and latex primer. If you don’t use a good quality oil-based or latex primer while painting your surface with acrylics, the paint will flake off and look terrible.
Acrylic paints give a softer exterior when dry. As a result, they easily attract dust and dirt. Here is when polyurethane comes in handy, as it will give added protection and a prolonged lifespan.
Why Should You Add Polyurethane to Acrylic Paints?
It’s no secret some paints are better than others. So when choosing paint for a new project, there are many things to consider.
If you have an acrylic paint project sitting around and want to give it a little something extra, or if you’re looking to change the style of your current project, you might be interested in adding polyurethane to your paints. So why should you add polyurethane to acrylic paints?
- Use polyurethane over acrylic paints because it provides a smooth finish. However, polyurethane isn’t completely smooth. But it will provide a smoother finish than acrylic paint.
- Acrylic paints are dry, dark, and dull. To add some brightness to the surface, add a polyurethane finish. Additionally, the clear poly coat protects acrylic paint from dirt and dust.
- Another reason is that polyurethane will maintain the Acrylic Paint color and shine. As I stated, acrylic paints dry dull, giving an undesirable look unlike when wet. However, adding a clear coat restores the color and remains shiny for an extended period.
How Soon Can You Polyurethane over Acrylic Paint?
This can depend on a few things, some being the type of surface you are painting and where you are painting it.
Generally, upon applying acrylic paint to your surface, you should wait between 24 and 72 hours before applying your polyurethane. During this time, you can make any necessary repairs that may be needed.
Waiting for a longer time gives outstanding results as the surface shall have completely dried and hardened, giving no room for complications.
The good news about this water-resistant finish is that it usually retains color when sitting out to dry and can be applied to any surface.
If the paint doesn’t dry well, the polyurethane will meddle with the acrylic paint creating a rough finish and making the surface prone to damage and wear.
In addition, wet acrylic paint could mix with polyurethane components, resulting in its resistance ability.
How to Apply Polyurethane over Acrylic Paint
One way to protect your acrylic paint is by applying a topcoat. In this case, polyurethane.
And If you are concerned about your paint color, use a water-based polyurethane. Oil-based one creates a yellow or amber hue or amber tint to light colors and white background.
Besides, an oil-based clear coat leaves a good finish but takes longer to dry. For a high gloss finish, use acrylic resin varnish.
To apply poly on your surface, follow the following steps:
Step 1: Wash the painted surface with warm water
First, clean the painted surface. The most commonly used cleaning agents are soaps, which are mostly available at home.
However, avoid the soap. They are usually harsh and would ruin the surface texture of the polyurethane, causing it to lose its gloss and give an unprofessional appearance.
Also, avoiding the latex remover on an affected color. They will most likely damage the surface texture of acrylic paint.
If you have any paint drips, use sandpaper or paint stripper to get rid of them, it will feel softer.
If the surface has wax, remove it using mineral spirits.
Step 2: Scuff the surface
Using 120-grit sandpaper, scuff the surface. Your goal is to flatten the sheen without producing deep scratches that might be visible after applying your polyurethane. Use palm sander.
If you are dealing with a painted floor, scuff the floor with a floor buffer and a 120-grit sanding screen. Wipe off the sanding dust using a tack cloth or a damp rag.
Step 3: Choose your applicator
To apply your polyurethane, be it water-based or oil-based, use a brush or a spray gun. You must not use a roller as it is bound to leave behind bubbles that may harden into the finish.
Polyurethane is thin enough for direct application, so don’t thin it. Adding more thinner may cause it to run.
Pour a small puddle of poly clear coat on an abandoned piece to see if it’s thick enough, then move to the next step.
Step 4: Apply one coat, then scuff before the next coat.
Upon application of the first coat, allow it to dry. The time required depends on the recommendations on the container.
Now scuff it lightly with 120-grit sandpaper to flatten any bubbles that hardened into the finish and remove dust particles and brush strokes on the surface.
Step 5: Apply a second coat
For outstanding results, do the same thing as in step 4. You shouldn’t apply more than two layers of polyurethane. Two is enough to get a glossy finish. Allow it the recommended time to dry before handing over the project.
How to Seal Acrylic Paint with Minwax Polycrylic Finish
When learning how to seal acrylic paint with Minwax polycrylic finish on raw wood, the process begins with essential preparation. The acrylic paint is applied with a brush or sponge and allowed to dry completely.
To seal your acrylic paint over Minwax clear coat, follow the steps below
- Pour the polyurethane in the corner of your painting surface and work it outwards from the corner using a foam brush. As you apply, try as much as possible not to break the surface tension.
- Do these till the whole painting is covered evenly.
- To apply the second coat, clean the brush thoroughly.
- Wait for 2 hours in between coats and apply 2 to 3 coats of polycrylic clear coat (as final varnish)to finish sealing your painting.
How Can You Determine If the Paint Is Dry or Cured?
To determine if the paint is dry, firmly touch the paint’s surface in a discrete area. If the paint is not sticky or tacky, then it is dry.
To determine if the paint is cured, poke the paint with your fingernail. If your nail leaves an indentation, then the paint is not cured. However, if there is no mark, then the paint has fully cured.
It is vital that you don’t apply a coat of polyurethane varnish until the paint has fully cured. Otherwise, the cleaning and sanding process will ruin the paint and could also damage the wood.
Will polyurethane Finish stick to all surfaces?
Yes, polyurethane will stick to most surfaces. But you must prepare the surface by cleaning to remove small dust particles, wax, or grease and let the surface dry before applying polyurethane.
Factors Affecting the Paint Drying and Curing Time
The first thing that will determine how quickly paint dries is heat. Just as liquids evaporate quicker when it is hot, so do wood finishes. The optimal temperature for drying is between 70 to 77 degrees Fahrenheit.
When the temperature drops below 50°F, the structure of the paint may begin to fail. Use a heat fan or HVAC to boost the ambient temperature where you are. If you have a thermostat, set the temperature at 70°F and leave the room while the paint dries.
Just as heat helps liquids dry faster, so does air. Proper ventilation will boost the drying time, just as a lack of ventilation will slow it down.
If you don’t have enough of a cross-breeze or you’re painting in a confined space, use a fan to speed up the drying process and get rid of the fumes.
High humidity is a problem before you paint and after. The excess moisture can be absorbed into the wood, which will then release bubbles when you paint over it.
You would find that even after a few coats, the paint will still be bubbling and eventually peel off. Humidity also slows down the drying process because it essentially adds more water to the liquid that’s trying to evaporate.
Use a hygrometer to measure the level of humidity. A good range is between 50% – 70%. To control excess humidity, use a dehumidifier. If the problem is too little moisture, use a humidifier.
4. Type of Paint
Some paints dry quicker than others, depending on the type, shade, and brand. In general, darker colors dry slower than lighter shades.
Different types of paint and vanish dry and cure at different rates:
- For example, chalk paint – dries in as little as 30 minutes, but you should wait at least a day before applying a second coat. It takes 30 days to cure. And you can put polyurethane over chalk paint.
- Milk paint also dries in 30 minutes and needs 30 days to cure.
- Latex/water-based paint – this dries in 4 hours and can be fully cured in 21 days.
- Oil-based paint – this takes between 6 to 8 hours to dry and at least 30 days to cure
- Velvet finishes – this furniture-friendly product dries in about 8 hours.
5. Type of Wood
Some woods have high concentrations of chemicals that prevent the paint from sticking properly and evaporating. Rosewood, in particular, can be troublesome, as can some aromatic cedarwood. If possible, avoid painting over this type of wood.
How to Clean up After You are Done Applying Polyurethane
You can wipe any messes on the floor with just soap and water if you are using water-based polyurethane.
Brushes can also be cleaned with soap and warm water if you are using water-based poly. However, if you’re using oil poly, soak the brush in mineral spirit to clean it and keep it for use next time.
What polyurethane is best over paint?
There isn’t a universal “best” polyurethane because each painting has unique properties and requires a different formulation of chemicals. However, if you need an oil urethane coating, the “highest quality” product is DuraKlear Plus from 3M Manufacturing.
How Many Coats of Polyurethane on Painted Wood and Floor?
You should use at least 3 coats of polyurethane over the painted surface. You might get away with one or two coats when using oil polyurethane.
However, you might need 4 or 5 coats before you get a smooth finish when using water-based polyurethane.
Follow the manufacturer’s suggestions, as some may require more or less, or read our in-depth guide on applying the right number of polyurethane coats for various situations, i.e., stairs and hardwood floors.
Can You Put Polyurethane Over White paint?
Yes, you can put polyurethane over white paint, but it is highly likely to be yellow.
This is the one scenario in which even water-based poly will yellow. As a result, many manufacturers tell you not to put it on white paint for fear you won’t like the outcome.
Learn how to spray polyurethane finish today.
Can You Put Water-based Polyurethane Over Latex Paint?
Yes, you can use polyurethane over latex and oil paints. You can use oil- or water based poly over latex paint to protect the wood. Wait for the paint to cure before applying poly fully.
However, as discoloration may occur with either type of polyurethane, test it out on an inconspicuous area first.
Can You Polyurethane Over Spray Paint?
Yes, you can put polyurethane over spray paint if you have given it time to cure. A good spray paint for wood needs at least 24 hours to dry. You should never rush the application of polyurethane on other finishes.
Can You Polyurethane Over Shellac?
You shouldn’t apply poly over shellac because shellac covers all. However, there’re cases where shellac-finished woodworks buff out white marks when a splatter of water gets on it and the fix is to strip off the shellac and refinish it with poly.
Recommended Reading: Can you shellac over paint?
Can you paint acrylic enamel over urethane primer?
Yes, but you need to sand the primer before painting. Acrylic enamel is an elastomeric paint-like material that can stretch and bend on surface irregularities like a primer.
Should I seal my acrylic painting?
Yes. Even if you intend to cover your painting with another coat of acrylic fully, it’s best to seal the initial painting with an isolation coat before putting another layer of fresh paint over it.
Does Mod Podge seal acrylic paint?
Yes, mod Podge glue seals acrylic paint because it can act as a sealant for various surfaces painted on, such as paper or wood. Mod Podge is a water-based sealant and adhesive, which will adhere to the fabric and other porous materials. However, it does not contain ultraviolet (UV) blockers which can cause yellowing or darkening of the surface over time, so it won’t provide long-term protection.
Cured Paint is Poly-Friendly Paint
As you have seen in this article, you can apply polyurethane over paint as long as it has cured. We have also made the important distinction between drying and curing so you don’t end up ruining your painting job.
If the paint takes too long to dry, you now know how to speed up the process.
With all of this knowledge at your fingertips, it is time to put it to the test. But first, you need to decide – will you be using water-based poly or oil-based polyurethane? I know what I’d choose.
Further, Read on: Can You Paint Over Polyurethane