August 19, 2021

Can you put polyurethane over chalk paint? | How to get perfect results

Yes, you can put polyurethane over chalk paint since it is water-tight, but that comes with challenges. It is not easy to get a smooth finish, although it is possible. It tends to be yellow over time. Products come with a manual with instructions. You must follow that when applying polyurethane over chalk paint for positive results. 

Is it easy to put polyurethane over chalk paint?

Polyurethane protects items from scratches and some forms of impact. Putting polyurethane over chalk paint is challenging since you must master a smooth finish. Applying polyurethane over chalk paint is an exercise that is worth the time and hard work. 

To ease the process, use a water-based formula such as Minwax. Anything else will have your surface yellowing sooner. If you pay attention to the application method, you will not have a difficult time. 

How much does it cost?

Look at the complexity, surface size, and location of the project. The chances are high that you will need an extra cost. Polyurethane foam injection ranges from 2,400 to 3,600. For small projects, it is $10 to $25 per square foot. For commercial use, it ranges from $8 to $20 per square foot. 

However, it is not affordable due to the ever-changing prices of raw materials. Changes in the supply and demand of raw materials make polyurethane prices unstable. 

Do you need to sand?

Chalk paint adheres to any surface area, and sanding is not necessary. However, there are chances that your first layer has bubbles or is not smooth. You need to sand. Sanding between coats is a good rule of thumb for a smooth finish on any painted surface, but the chalky nature of chalk paint makes it easy. Sanding makes the process easier, faster, and flawless.

How to apply polyurethane over chalk paint

The chalk paint has to cure before a protective coat. Dry the item for seven days before applying polyurethane. That makes sure it adheres to the surface before a protective coat. Prepare your tools and materials. 

These include a brush, sandpaper, and polyurethane. A high-quality paintbrush performs better and applies a thin coat over the night on the surface. When dry, lightly sand the coat using 220 grit sandpaper. That is on areas that are rough to touch. 

Apply a second coat of polyurethane and let it dry over the night. Sand again, and if there is a need to add polyurethane coats, repeat the process. Thin coats are ideal, allowing the product to dry before you pile multiple layers. 

How long does it take to dry polyurethane? 

Water-based and oil-based polyurethane take different times to dry. Water-based polyurethane dries faster than oil-based polyurethane as it takes 4 to 6 hours so that you start walking on the surface. After 24 hours, the product is dry to place items. After 48 hours, you are allowed to move your furniture. 

It takes 30 days to cure water-based polyurethane, and it is ideal to start using mats and rags. Oil-based polyurethane takes 24 hours to dry, and you may start walking on top of the surface. That drying time does not accommodate pets and shoes. When the first coat dries, add another coat, and After 48 hours, you may start walking on the surface. 

Wait for four days if you intend to put furniture on the surface. Speeding up the process is possible by opening windows and doors. A good ventilation system is required during the drying process since it speeds up the ventilation process. Adding a fan to the room also improves the circulation of air. 

How long does polyurethane take to cure

There are two phases in which the oil-based polyurethane dries. The thinners evaporate, and as the oxygen in the air combines with the varnish, the curing process starts. Curing makes the finish hard and durable. 

There is adhesion to the floor. The curing process takes 30 days or more. There is a need to regulate the process rather than wait for 30 days. Environmental conditions control the pace at which the chemical dries. The thickness of the film affects the drying time, and the number of coats contributes to the time taken when drying polyurethane. The lack of order tells us that the chemical has not dried yet. 

Sand the chalk paint

Since chalk paint is applied in multiple layers, there is a need to sand the chalk paint between coats. That helps in adhesion, except for the final layer. Sanding exposes the natural look of the wood underneath. Lightly sand the paint so that the process does not damage the surface. 

Sanding methods are to be applied to expose each layer’s beauty. Smooth out the layers with fine 150-grit sandpaper. Sanding between coats is a rule of thumb that gives you a smooth and beautiful finish. A thin coat of wax finalizes the process as it seals the paint. 

Apply polyurethane

Polyurethane is a liquid-based topcoat that is applied using a brush or a spraying bottle. It is ideal for high-traffic surfaces. Depending on what you prefer, you have multiple finish options, from satin to glossy. 

It gives you water-tight protection, and that explains the multiple coats. You are allowed to roll polyurethane over chalk-painted surfaces, and it is quick to apply. Add paint color if you want, giving your item a different look. 

The ease of use of the product makes it ideal for DIY users. Stains appear in the chalk paint underneath the polyurethane, which is dealt with by adding more coats until satisfied. Brushstrokes give you impressive results as well. 

Apply another coat of polyurethane

The first coat is streaky, and there is a need for a second coat. Allow the first coat to dry and sand so the second coat has an excellent adhesive to the surface. Work on the surface if you feel thick in spots, or you can feel the ridges of dried paint left by your paintbrush. That covers the flaws. Please pay attention to the bubbles so that you sand them off and apply a smooth second coat. A second coat on top of poorly done skin ruins the final product. 

Apply a third coat of polyurethane 

After two coats of polyurethane, a third coat is necessary since it seals and protects the layers underneath. Testing a small patch first is ideal so that you know the procedure to follow when you start applying polyurethane. If you are running under a tight budget, two coats are enough but make sure you try to be flawless as you use the chemical. 

David D. Hughes

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