Buffing Water-Based Polyurethane: Worth The Effort?

Buffing is a great way to achieve a glass-smooth finish on wood. It is a simple process that can be done by hand or with a power tool, and it works for both oil-based and water-based polyurethane. Here's a step-by-step guide on how to buff a water-based polyurethane top coat:

Step 1: Apply a Thick Coating

First, apply at least three coats of polyurethane, preferably four. This will ensure that you don't buff through to the bare wood. Sand lightly with 220-240 grit sandpaper between coats, and let the last coat dry for at least 24 hours.

Step 2: Level the Surface

Use a piece of old 240-grit sandpaper wrapped around a block of styrofoam to lightly sand the surface in the direction of the grain. This will remove any dust bumps and create a smooth, level surface. Be careful not to over-sand, as you don't want to go through to the bare wood.

Step 3: Power Buffing

For large, flat surfaces, use a random orbit sander with a superfine 3M rubbing pad. This will buff out any tiny imperfections and create a smooth, even sheen. Work slowly in a grid pattern, and use a bright light to highlight areas that need more work.

For curved surfaces and tight spaces, you can use #0000 steel wool or a rubbing pad by hand to buff hard-to-reach areas.

Step 4: Apply a Wax or Polish (Optional)

If you want a shinier finish, you can apply a coat of automotive polish or paste wax and buff it out with a soft cloth. Skip this step if you want a flat, matte finish.

Tips:

- It's important to minimize imperfections when applying the polyurethane. Work in a low-traffic area with minimal dust, and vacuum the project and the floor before starting.

- Use a sponge roller for large surfaces instead of a paintbrush to avoid brush marks.

- Thin the polyurethane slightly when using a brush, and avoid going over the surface multiple times.

- Choose the right gloss for your expectations. You can't buff a matte gloss polyurethane to a high shine, so check the labels for high gloss, semi-gloss, matte, or flat.

- Only sand and buff the first coat and any coats in between. Do not sand the final top coat until it is completely dry.

- Wait 24-48 hours before buffing water-based polyurethane, and 7-14 days for oil-based polyurethane.

- Do not wet sand if you are a beginner, as it is easier to accidentally sand through to the wood.

How to buff a water-based polyurethane top coat

Buffing a water-based polyurethane top coat can be done in several ways, depending on the tools available and the desired finish. Here is a step-by-step guide on how to achieve a smooth, polished finish:

Step 1: Prepare the Surface

Before buffing, ensure the polyurethane finish is thick enough to work with. Apply at least three to four coats of polyurethane, with light sanding (220 to 240 grit) between coats. The final coat should be allowed to dry for at least 24 hours.

Step 2: Level the Surface

Use a piece of 240-grit sandpaper wrapped around a block of styrofoam to level the surface and remove any tiny bumps caused by dust. Sand lightly and in the direction of the grain until the surface feels smooth.

Step 3: Buffing Techniques

There are several techniques for buffing a water-based polyurethane top coat:

• Dry Buffing with Sandpaper: Use Mirka Royal Micro sandpaper, starting with 1500-grit. Make 2-3 passes on a small area and evaluate the results. If necessary, switch to a heavier grit to remove surface irregularities, then finish with 1500-grit.
• Dry/Wet Buffing with Abrasive Pads: Start by dry sanding with Abralon 2000-grit, then 4000-grit. If needed, lubricate with General Finishes Satin Finishing Wax, mineral spirits, or naphtha (never use water). One sheet of 1000-grit or 1500-grit should be enough for the entire surface when lubricated.
• Buffing with Polishing Kits: Spray Presta polish on a buffing pad and apply a small amount to each section of the surface. Continue section by section, misting the pad when it gets dry. Buff the entire surface with a microfibre cloth to remove any splatter.
• Power Buffing: Use a random orbit sander with a superfine 3M rubbing pad. This will buff out any tiny imperfections and create a smooth, level finish. Work slowly and evenly in a grid pattern, using a bright light to highlight areas that need more attention.

Step 4: Final Touches

Depending on the desired finish, there are a few final steps to enhance the shine:

• For a glossy finish, use car polish and a foam buffing pad in an orbital sander. Spread a small amount of polish on the pad and work it into the surface with light pressure. Finish by wiping down with a polishing cloth to remove any excess.
• For a satin finish, use paste wax and a polishing pad or cloth. Apply a small amount of wax and work it into the surface with smooth, horizontal motions, following the direction of the grain. Remove any excess wax with a paper shop towel before it dries.

The best tools for buffing

Buffing a water-based polyurethane finish can be done using a variety of tools and techniques. Here are some of the best tools and methods for achieving a smooth, glossy, or satin finish:

Sanding Tools

• Sandpaper: Use fine-grit sandpaper, such as 1500-grit or 2000-grit, to buff the finish. Start with a higher grit and work your way down to a finer grit for a smoother finish. You can also use a lower grit, such as 320-grit, if that's all you have available.
• Orbital sander: An orbital sander can be used with the sandpaper to speed up the buffing process. Set the sander to a low power setting and work in slow, horizontal motions. You can also use a random orbit sander, which vibrates and rotates to buff the surface.
• Scrubbing pad: If you don't want to use sandpaper, you can attach a scrubbing pad to your orbital sander. This will buff the finish without the need for sandpaper.
• Brown paper bag: In the absence of sandpaper, a brown paper bag can be used to buff the finish by hand.
• Styrofoam block: Wrapping the sandpaper around a block of styrofoam can help to apply even pressure when buffing by hand.

Polishing Tools

• Car polish: Apply a clear car polish to the finish using a foam buffing pad attached to your orbital sander. Spread a grape-sized amount of polish and work it into the finish using slow, horizontal motions.
• Polishing cloth: Use a soft, clean cloth to wipe down the finish and remove any excess polish. You can also use a polishing cloth to apply automotive swirl mark remover, which will help to create a glossy finish.
• Paste wax: For a satin finish, use car paste wax and a polishing pad or cloth to buff the surface. Apply the wax in the direction of the wood grain using short, smooth motions. Remove any excess wax with a paper shop towel before it dries.
• Steel wool: #0000 steel wool can be used to buff the finish, especially in curved or detailed areas. Be careful, as steel wool can catch fire easily. Store it in a tightly sealed metal container when not in use.

The best grit for buffing

Buffing is an effective way to achieve a glass-smooth finish on wood. It can be used to deal with brush strokes, bubbles, and uneven results. The best grit for buffing depends on the stage of the buffing process:

Sanding between coats

When applying multiple coats of polyurethane, it is recommended to sand lightly between coats with 220-320-grit sandpaper. This will help create a smooth foundation for the next coat.

Sanding after the final coat

After the final coat, start with 320-grit sandpaper, then move to 400-grit, and finish with 600-grit sandpaper. Sand in alternating directions with each abrasive to make it easier to identify any remaining scratches from the previous grit.

Removing dust nibs

To remove any remaining dust nibs after sanding, use 1500-grit sandpaper or a piece of brown paper bag.

Power buffing

For power buffing, use a superfine 3M rubbing pad, which is a thick, non-woven, synthetic abrasive material. Cut it into a 6-inch by 6-inch piece and place it on your workpiece before putting your random orbit sander on top.

Wet sanding

Wet sanding is an effective way to ensure a smooth finish on polyurethane. Use an orbital sander with 2000-grit sandpaper and work in slow, horizontal motions across the surface. If you don't have a handheld tool, you can also sand by hand with 1500-grit sandpaper or a brown paper bag.

How to buff without an electric sander

Buffing a water-based polyurethane top coat can be done in several ways, and one of them is by using an orbital sander. However, it is important to note that orbital sanders are not ideal for large surface areas and work better for smaller projects. Additionally, they require different pads for buffing than for sanding, so it is crucial to have the right pad type.

• Choose the Right Sandpaper: Select sandpaper with a grit of 320 or higher. This ensures that the sandpaper is fine enough to buff effectively without causing damage to the surface.
• Install the Sandpaper: Securely attach the sandpaper to the orbital sander, ensuring it is centred on the pad.
• Attach a Polishing Pad: Attach a polishing pad to the orbital sander's hook-and-loop pad. This helps distribute the polishing compound evenly.
• Apply Polishing Compound: Spread the polishing compound evenly on the surface you want to buff.
• Buff the Surface: Turn on the orbital sander and slowly buff the surface in a circular motion. Apply even pressure and avoid staying in one spot for too long to prevent damage.
• Clean the Surface: After buffing, use a clean cloth to remove any residue from the surface. You may need to repeat the process if the desired level of polish is not achieved.

It is important to note that orbital sanders have limitations when used as buffers. They are not designed for polishing and may not achieve the same level of shine as dedicated buffers. Additionally, using the wrong pad or polishing compound can lead to damage to the surface.

If you are looking for a high-gloss finish, the following techniques can be used:

• Dry Buff with Mirka Royal Micro Paper: Start with 1500-grit sandpaper and gradually increase the grit if surface irregularities are not fully removed. Finish with 1500-grit paper.
• Dry/Wet Buff with Abralon Polishing Discs: Begin with dry sanding using 2000-grit, then 4000-grit Abralon discs. If needed, lubricate with General Finishes Satin Finishing Wax, mineral spirits, or naphtha (but not water).
• Buffing/Polishing with Presta Polishing Kits: Spray Presta polish on the buffing pad and apply a small amount of polish to one section at a time. Spread it with the pad and mist the pad with Presta lubricating material when needed.

These techniques, suggested by Jeff Jewitt of Homestead Finishing Products, can help you achieve a high-gloss finish on your water-based polyurethane top coat without using an electric sander.

How to buff a previously finished surface

Buffing is a surface treatment process that smooths and polishes a surface to achieve a glossy and refined appearance. It is commonly used in the automotive, woodworking, and metalworking industries, and can be applied to materials like metals, plastics, and wood.

• Surface Preparation: Ensure the surface is clean and free from dirt, dust, or debris. If the previous finish is still intact, you may need to strip it completely. For waxed surfaces, use water and ammonia to strip the wax. For other finishes, you may need to sand down to bare wood.
• Selection of Buffing Compound: Choose a buffing compound suitable for the material and the level of imperfections. Coarser compounds are used for removing deeper scratches, while finer compounds are used for achieving a high-gloss shine.
• Selection of Buffing Equipment: Pick the right buffing equipment for the task. This includes buffing wheels or pads made of materials like cotton, sisal, or foam, used in combination with buffing machines.
• Executing the Buffing Technique: Apply consistent pressure and maintain a steady speed during the buffing process. Move the buffing wheel or pad in a controlled manner, following a specific pattern to ensure even coverage. Start with a lower speed and gradually increase it.
• Inspect Your Progress: Regularly check the buffed surface during the process to evaluate the results. Make adjustments or repeat buffing steps if necessary.
• Finish with a Top Coat: Once you have achieved the desired level of shine, you may want to apply a final top coat to protect and enhance the finish. This could be a clear coat, wax, or another type of sealant.

Some additional tips for buffing a previously finished surface:

• Always wear appropriate protective gear, such as safety goggles and gloves, when performing buffing.
• If you are new to buffing or working with a new material, practice on a small test area first.
• Different types of buffing include dry buffing, wet buffing, color buffing, and high-speed buffing. Choose the technique that best suits your material and desired outcome.
• If you are buffing a water-based finish, never wet sand the surface.
• For best results, follow the grain of the wood or material when buffing.

By following these steps and tips, you can effectively buff a previously finished surface to achieve a smooth, glossy, and refined appearance.

Frequently asked questions