A mirror-smooth finish is what every woodworker dreams of when finishing their wooden creations with polyurethane. Nonetheless, many beginners and the not so experienced handyman never realize this dream.
After all the hard work the results in most cases turn out a little less than impressive. You might find a brushstroke mark here, some bubbles there, and dust nibs everywhere, an outcome you can’t really be proud of.
In an attempt to achieve a perfect smooth polyurethane finish, a common miscalculated move is to apply a fresh coat in the hopes that with extra care, it will be better than the last.
Considering the amount of time it takes polyurethane to dry, there’s always going to be a bug lurking in the air somewhere waiting to mar it once again. It could be lint, hair, dust, etc.
The secret to a flawless polyurethane finish is buffing. It is that simple. Buffing works magic not just for polyurethane but for a variety of other finishes including metal.
So how do you buff polyurethane? To buff polyurethane, use sandpaper to smooth down the surface, clean it off, and then using a buffing pad (by hand or with a sanding tool) in even, circular motions to slowly work the whole surface. You can also apply a wax or polish for a finish with greater shine.
In this article, we will guide you on how to buff polyurethane on wood projects with easy step by step directions. You will also find tons of helpful pre-buffing tips you can use when applying polyurethane for the best results.
Tools and Materials Needed to Buff Polyurethane
First things first. You’ll need to gather the right materials before you can do anything with that polyurethane finish!
Fine Grade Finishing Papers
Fine grade finishing paper such as micro-mesh with very little abrasion power is ideal for buffing and polishing jobs.
Anything between 1500-2000 grit is ok. You just want to get rid of tiny protrusions, not scratch out the entire film of polyurethane.
Don’t have one? Try the back of a brown paper or fine steel wool (#0000). They work just fine. Leftover medium grit sandpaper is another alternative. It is less coarse having previously sanded a couple of times already.
A hand-sized block of styrofoam, a foam pad, felt or anything with the same density – in between hard and squishy – will do. It offers your hand some resistance when you press too hard. Don’t worry, you won’t need this when you get the hang of things through experience.
There’s an assortment of fancy rubbing and buffing pads in many hardware or home improvement stores. Choose one with a super fine abrasion level.
An orbit sander will be effective and faster for big projects and your arms will thank you later. If you don’t already own one, you could still just do things manually using your hands. Besides, the tool won’t access contours.
Rubbing Compound (Optional)
Rubbing compounds are chemical abrasive formulas that deal with tiny scratches by flattening them out or sealing them in.
Automotive Polish or Paste Wax (Optional)
Are you after a piano-like reflective glow, a low profile sheen like satin?
Automotive polish will give your surface excellent glossy shine while paste wax will give it just a hint of sheen. However, you do not need these if a flat or “matte” look is what you are after.
A Bit of Patience
Knowing how to buff polyurethane alone is not enough. You need a little patience to finally see desirable results, especially if you’re new to working with polyurethane!
How to Buff Polyurethane – Step By Step
Buffing polyurethane is pretty simple. But if you’re new to the process, here’s how to do it:
Step 1: Sand the Surface
Take the fine-grit sandpaper and wrap it around the block of styrofoam. (This helps you hold the paper better.)
Begin sanding the surface. Use back and forth motions following the direction of the grain until you cover every inch and level the entire surface.
Work very lightly, exerting just the right amount of pressure to kick out the imperfections without getting through to the wood. Be extra cautious at the edges. The film there is very delicate.
Look at the surface from an angle and feel it with your hands. It should feel very smooth but appear dull. Any rough to touch shiny spots still need a couple more passes.
Step 2: Clean Off the Surface
When satisfied, use a lint-free cloth to wipe away any powder from scraping the surface.
You may apply a fine cut cleaner or a swirl remover at this point for extra smoothness.
Step 3: Begin Buffing
Next, place the buffing pad on the surface and bring the sanding power tool above it such that the pad is sandwiched. Switch on the tool and set it on low speed.
The orbit sander will cause the pad to spin buffing the wood even, clean and shiny. But you can use circular motions if doing this by hand.
Move gradually in a defined pattern until you cover the entire area. The more you buff the shinier it gets.
For areas where the power tool can’t maneuver (such as curves, panel joints, trims, and gorges), you may have to buff by hand.
Step 4: Polish it Off (Optional)
When done, squirt a small amount of automotive polish or wax on a soft cloth, rub it all over then power buff the entire wood again. You can skip this step if you want a flat-matte finish.
But if you’re a visual learner, here’s a great tutorial from Home Built Workshop:
A Quick Note About Wet Sanding
If you prefer to wet sand, follow the same steps above on how to buff polyurethane. Just make sure you are using a wet/dry fine-grit sanding paper instead.
You will also want to soak it in water for a few minutes before beginning.
You should also start on a wet surface by spritzing it with water first. You can wipe away any excess slurry using a clean damp cotton cloth.
Afterward, wait for the surface to dry and then continue with the remaining steps after sanding (as above).
Tips For Buffing a Polyurethane Finish
You probably already know how to apply polyurethane on wood, and hopefully like a pro. How you apply it determines the ease and outcome of buffing the final coat.
While buffing will really smooth out and shine your finish, you want to deal with as few flaws as possible. Buffing will not turn around a shoddy application.
Also, buffing a coat that is not ready will ruin everything and you might have to start again from scratch. It is therefore imperative that you observe the following nitty-gritty details when applying polyurethane finish on the wood.
Here are some other tips to help you get the job done perfectly.
1. Only Buff Thick Coating
Buffing involves light sanding. With a thin layer, you can’t trust yourself as a beginner not to get through to the wood. This doesn’t mean going overboard with several thick layers, however. Apply 3-5 regular films with thorough sanding in between.
2. Never Buff Uncured Polyurethane
Dry the coat of polyurethane entirely before buffing it.
Solid hard dryness may take 48 hours for water-based polyurethane and a few more days, sometimes even weeks after application for oil-based ones. It depends on temperature and humidity. You will know it is ready when it becomes odorless.
3. Minimize Imperfections
A dust bump here and pesky bug prints there is almost inevitable even for world-class woodworkers. Still, you can make a few adjustments to how you apply polyurethane to minimize them.
Here’s a collection of ingenious ideas gathered from experts:
- Working from a low traffic area
- Creating a makeshift drying booth using shower curtains or poly sheets as walls and a roof
- Vacuuming your floor and the project before commencing the application
- Doing finishing a few hours or a day after sanding when the dust has settled from the air
- Eliminate brush streaks and uneven coating by changing tools. For vast surfaces, use a sponge roller as opposed to a paintbrush. A wipe-on polyurethane does wonders for smaller parts.
- Spraying the final coat yields the least flawed finish than brushing or rolling. If you must use a brush, thin the polyurethane a little extra and avoid going over the surface many times.
4. Choose Gloss Appropriately
No amount of buffing will transform a matte gloss polyurethane to a high glossy shine. Therefore, ensure you are getting a product with the right gloss for your expectations.
Check the labels for high gloss, semi-gloss, matte, and flat.
Should You Sand the Final Coat of Polyurethane?
No, you do not. Only the first coat and any other coat after except for the top one. You will only sand very lightly when buffing the topcoat and this is done once completely dry.
How Long Should You Wait to Buff Polyurethane?
Ideally, you should wait 24-48 hours for water-based sealants and 7-14 days for oil-based ones. However, it may take much longer to cure depending on surrounding conditions.
Should You Sand Wet or Dry When Buffing Polyurethane?
Both methods are okay, though we would not recommend wet sanding for beginners. If you make a slight mistake and sand through the polyurethane, water will seep into the wood. Consequently, the grains will be raised creating more problems.
Can You Use a Rubbing Compound on Polyurethane?
Yes, a rubbing compound may be used on polyurethane if compatible. Being a mild abrasive it will tackle small scratches and marks by smoothing them out.
Can You Wax Over Polyurethane?
Yes, you can wax over polyurethane to cover small blemishes and give the top coat a nice luster making the wood pop. Just be sure to buff away any excess.
Can I Restore an Old Coat of Polyurethane by Buffing?
Yes, an old coat of polyurethane can be restored by buffing. It doesn’t have to be something freshly built. Even an old surface with dings and scratches can be buffed back to its days of shining glory.
Learning how to buff polyurethane is the secret to an incredibly sleek shiny blemish-free finish. Timing is key. Doing it too early is what messes things up. The longer it is cured the better the results.
Laying a good foundation is equally important. The correct application always makes all the difference. Remember, buffing will help you attain that high-end finish you’ve always yearned for only if you started right.
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