Polyurethane is a coating agent that is applied to wood to protect it from wear and tear. Whatever the base material, polyurethane is available in many varieties, from glossy to matte. The use of polyurethane is quite simple, starting from surface sanding, polyurethane application, and repetition. However, depending on the shape of the surface area being worked on, you'll need to determine whether the polyurethane should be rubbed with a brush or a cloth.
Step
Part 1 of 4: Preparing the Workplace
Step 1. Clean your work area
Remove as much dirt and dust from your workplace as possible. Vacuum, mop, and/or wipe each surface clean. Reduce as many particles as possible that can stick to the polyurethane.
If you remove dust and other particles while they are already on the polyurethane, the surface will be uneven
Step 2. Improve the airflow of the room
Make sure the air flows smoothly in the room to get rid of the polyurethane fumes while you work. Open the window and install the exhaust fan (hexos) pointing outward. If possible, open a window across the room.
- Never place the fan directly on the job site as dust can be blown onto the wood when you apply polyurethane.
- Purchase a respirator with an organic cartridge if you are unable to circulate the room air and/or are sensitive to vapors.
Step 3. Prepare the work surface
If the wood to be processed can be moved, lay out a protective layer so the wood can lie on top of it while you work. Use a tarp, cloth, cardboard, or other similar material. Regardless of the material used, make sure that the area exceeds at least 30 cm from each edge of the wood. Thus, the workplace will be easier to clean.
Also, make sure that there are no items that shouldn't be soiled in the area around your workplace, in case your work gets quite messy
Part 2 of 4: Preparing the Wood
Step 1. Scrape off all the old covering
Scrape off any residual lacquer, wax, varnish, or paint that is still on the wood. You may temporarily move your work outdoors. Work in a well-ventilated area while simplifying your wood cleaning process.
Step 2. Smooth the wood with sandpaper
Start the smoothing using a medium-rough (100 grit) sandpaper if your wood is rough enough. After that, sand it again with fine sandpaper (grit 150), and continue with extra fine sandpaper (grit 220). Inspect the wood for scratches on any sanding. If needed, use extra-fine sandpaper to smooth out the scratched area.
Step 3. Clean the wood
Use a vacuum cleaner to remove sanding powder from the wood and the area around it. Place a soft brush head on the vacuum cleaner before vacuuming the wood to prevent scratching on the surface. After that, dampen a lint-free cloth and wipe the remaining powder on the wood that hasn't been sucked in by the vacuum cleaner. Repeat wiping with a dry microfiber cloth.
- If the polyurethane is oil-based, use mineral spirit to moisten the lint-free fabric.
- For water-based polyurethane, wet your cloth with water.
- Some people use a tack cloth to dry the wood, but be careful because some tack fabrics contain chemicals that will interfere with the adhesion of the polyurethane.
Part 3 of 4: Determining the Technique to Use
Step 1. Wipe the flat surface of the wood with a brush
Apply a large portion of the wood surface at a time with a brush. Reduce the number of layers needed because the brush produces a thick layer. We recommend using a natural bristled brush for oil-based polyurethane, and synthetic bristles for water-based polyurethane. When using a brush:
- Dip the bristles 2.5 cm deep into the polyurethane.
- Apply the polyurethane to the wood in a long, even motion.
- After each application, run the brush over the dripping area so that the polyurethane spreads evenly over the wood.
- Overlap each half of the previous spread so that the polyurethane coating on the wood is smooth and even.
- After each coat, check again for drips that need fixing.
Step 2. Wipe the contoured surface
Avoid drips that can appear from the application area that is not completely flat. This technique usually results in a thin layer so double the amount of application you would normally apply with a brush. When using a washcloth:
- Fold a clean cloth into a square, about the size of your palm, to wipe the wood with polyurethane.
- Dip the edges of the fabric in the polyurethane.
- Rub the cloth on the wood following the groove.
- Overlap each half of the spread so that the results are even.
Step 3. Spray polyurethane on hard-to-reach areas
Purchase spray polyurethane if the area you want to coat the wood is difficult to reach with a brush or cloth. Be careful and spray the polyurethane in a small spray so it doesn't drip. Make sure you cover all surfaces around the work area to avoid spraying the polyurethane.
- Spray polyurethane produces an extremely thin layer.
- Test first in a small area to improve your technique.
Part 4 of 4: Using Polyurethane
Step 1. Stir the polyurethane
After opening the can, use a stirring stick to thoroughly mix the polyurethane components, which may have separated and settled over time. Always stir your polyurethane instead of shaking it. Whisk will produce bubbles in the polyurethane which can transfer to the wood so it doesn't spread evenly when applied.
Step 2. Seal the wood
Use a clean container to mix the polyurethane and mineral spirits. Combine 2/3 polyurethane with 1/3 mineral spirit in this new container. Apply or rub a layer of this mixture on the wood. Wait for it to dry before continuing.
Pure polyurethane takes 24 hours to dry, but polyurethane diluted with mineral spirit should dry faster
Step 3. Sand back your wood
From this point on, always sand the wood before applying a new coat. Remove any streaks, drips, bubbles, or brush marks that are still visible on the wood. Use extra fine sandpaper (220 grit) to reduce the chance of scratching the wood surface. When you're done, vacuum and wipe the wood again to get rid of all the particles.
Step 4. Apply the first coat
After sealing the wood, use pure polyurethane. However, continue to pour some of the polyurethane into a clean container, instead of dipping the brush or cloth directly into the polyurethane can. Do not allow any dust or particles that may get caught in the brush or cloth, which mixes with the main polyurethane in the can.
- When greasing, repeat the entire surface area of the wood with the brush without dipping it back into the polyurethane can, after the first coat is finished. Smooth out all drips and streams on the wood.
- After that, let stand for 24 hours so that the polyurethane can dry.
Step 5. Repeat
After the first coat has dried, sand back your wood. After that, add a second layer in the same way. Wait again for 24 hours. If you're using a brush, two layers should suffice. For all areas where the cloth or spray was applied, repeat two more times for a total of four layers.
