Brushing vs. spraying water-based polyurethane
Several ways of applying water-based polyurethane include brushing, spraying, and wiping. The most frequently used one is brushing.
Yet nowadays, more people prefer spraying water-based polyurethane because spraying is easier and creates a better factory-looking finish.
As brushing requires fewer tools, this method has several downs, like creating more bubbles, more sanding, and sticking polyurethane (not soaking).
For furniture or woods with a plain surface, spraying is more effective. For furniture with edges and curves, including table legs, brushing is more suggested as it can reach between cracks better.
Filling cracks by spraying water-based polyurethane makes uneven coating. So based on your projects, choose the one more suitable for you.
Why the water-based polyurethane for spraying
As polyurethane is available in oil, water, and combination-based type, the water-based one is more recommended for spraying.
The oil-based one is thicker in terms of consistency, making it difficult to be sprayed. In contrast, water-based polyurethane using water as the solvent has a thin flow.
For thinning, not all types of water-based polyurethane need thinning. The ones that come with the spray cans usually do not require thinning.
As a result, spraying water-based polyurethane will not make it turn yellow on white surfaces or paint.
You do not need certain techniques or dozens of tools during the spraying process. Further preparation is explained below.
Finally, it dries quickly, so you should spray it in a moderate amount. Too little will dry in an instant, and too much will need more drying time. Lastly, water-based polyurethane is the friendliest for the environment.
Things to prepare before spraying water-based polyurethane
Tools that you may need to prepare before the spraying process include a face mask, a pair of gloves, sandpaper, sanding sealer, paint thinner, paint sprayer, painter’s tape, and drop sheets.
You can use any sprayer, like compressed paint sprayers, spray guns, or an airless paint sprayer. You do not need to separate the sprayer for polyurethane or other water-based paints.
If you refill the sprayer with water-based polyurethane, thinning is necessary. Yet if you use water-based spray-on polyurethane, all you need to do is just shake the can.
There might need more tools for spraying water-based polyurethane based on the furniture/woodwork you create. For example, spraying wood for floors also needs knee pads, a roller tray, and a floor finish applicator.
Spraying water-based polyurethane step-by-step
Generally, spraying water-based polyurethane consists of four main sections. They are setting up the workplace, tools, and materials, preparing the wood surface and polyurethane, spraying, and drying and cleaning.
- Prepare all tools you need and check the environment of your workplace, including the ventilation, temperature, PPE, and sheet for preventing stains on the floor or other furniture.
- Using sandpaper, smooth the wood surface. After that, apply a sanding sealer to keep the surface smooth and even. Sand on the sanding sealer surface so the polyurethane will stick well
- Using the proper solvent and ratio, thin the polyurethane to the right consistency. Add into the sprayer. If you use the spray-on water-based polyurethane, there is no need to do this step
- On a different wood, test the sprayer first. Check whether the result dries well and has a smooth surface. The recommended pressure is between 26-29 PSI. Ideal coats are 2-3; for each coat, let it sit for 3 hours.
- For the last coat, let it dry for 24 hours. Then, you can clean it with water and gentle soap or check the brand’s guidelines. It will be best to clean it with a spray gun.
Tips on spraying water-based polyurethane
- Check the wood or furniture that you spray. Then decide on the right spray pattern and direction.
- While spraying water-based polyurethane, maintain a firm wrist for long, steady, and continuous movement. Hence the surface will be even with no less or denser coated areas, drips, and runs. Don’t stop in the middle of spraying. Finish a stroke first, then create a new one.
- After each spray, look at your result from different angles in the reflective direction to check its thickness and adhesion. So you can add or correct the area.
- Provide ventilation for clear air movement. Since spraying could create a strong odor, besides a face mask, the ventilation helps to save your lungs. Then make sure that the wind or air movement is dust-free, or the finish layer will have bumps from the floating dust.
- For the last coat, use synthetic abrasive. Then for each coat, choose coarse to medium synthetic wool. Do not use steel wool as its steel bits might stain the coat.
Warnings for spraying water-based polyurethane
Preparing a room with a hot temperature might be good for drying polyurethane. Yet if it’s too hot and dries too fast, the surface can get cracks and textured bumps, making it feel rough.
If you want to make it hotter, just raise the temperature to 1-3 degrees Celsius. Meanwhile, spraying water-based polyurethane at low temperatures creates orange peel effects, so spray it at the right temperature.
While preparing the polyurethane, do not shake or create many movements causing bubbles. Check its expiry date and the wood type that you’re working on. Oily wood will not work well with water-based polyurethane.
The proper thinning before spraying water-based polyurethane
The proper solvent to thin the water-based polyurethane includes water, water-based paint thinner, and denatured alcohol.
The added solvent should be 2-3% until reaching the ideal consistency. For more detailed measurements, check the brand since each has a different application measurement.
After pouring the solvent into polyurethane, gently stir the mixture without shaking. Then transfer some of the mixtures to test using the sprayer.
If the consistency is not similar to the desired, add 2-3% water. The cap for adding water/solvent is 10%.
Benefits of spraying water-based polyurethane
- The furniture’s surface has a better and even coverage.
- The process is easier and faster.
- Less chance of having strokes, bubbles, or bumps on the surface.
- The drying time is shorter than the oil-based or other finish.
- When spraying water-based polyurethane, the polyurethane doesn’t atomize, especially with an air-assisted or airless sprayer.
- The fumes of the spraying process can be reduced vastly, and safer for the environment and the human body.