Can you apply a second coat of polyurethane without sanding?
Respected finishing expert Bob Flexner suggests that sanding between coats isn't necessary for proper adhesion between coats. He (and pretty much everyone else) recommends doing it anyway, mostly in order to get rid of the dust nibs.
Polyurethane doesn't do that so it needs a mechanical method to stick to the previous coat. If you don't sand, the varnish will flake over time particularly if it is a high wear surface. It will also make the surface much smoother.
You must sand in order to remove all traces of previous coatings. This is to open the pores of the wood so that it can absorb the new finish. If you just applied without sanding the result would be terrible. Polyurethane will not stick.
Water-based polyurethane requires at least two hours of dry time between coats, and you should only apply two coats in a day.
I've been using polyurethane for 40 years or more. I prefer the 320 grit between coats. Try to get the "non-filling" type, like the waterproof or aluminium oxide. After the first coat, all you are trying to do is remove the bumps and scuff the surface for the next coat, so 220 is just too rough.
A wet sander can be used after sealant, varnish, or polyurethane has been applied to smooth out bumps, scratches, or imperfections on the surface. In addition to making scratches less visible, the water gives better control over the thickness of the finish.
- A 6-in. rollers lets you apply the poly fast and evenly. ...
- Don't freak out when you see the finish right after you lay it down. ...
- After each coat, re-dip the roller in mineral spirits and put it into a zippered plastic bag for the next coat and leave the wet tray to dry.
Allow each coat to dry fully. To give the subsequent poly layers something to bond to, sand lightly between coats with 320-grit sandpaper wrapped around a hard block. Note: The first coat needs the most sanding to appear smooth; don't worry if it doesn't look as flawless as you'd like at first.
Do I need to sand off old finish completely before applying polyurethane? Generally speaking no, you don't need to completely remove previous finish to apply more of the same finish or a different (compatible) finish1.
It requires around 2 to 4 hours for a water-based polyurethane and 6 to 10 hours for an oil-based to cure and eventually be subject to a second coating. Figures as these still vary depending on the type of base, humidity ratio, air pressure, and even the state of the woodwork.
How do you apply a second coat of polyurethane?
If you want the smoothest finish possible, then wait until it is dry, very lightly sand with very fine paper (220 or finer) to remove any dust bumps, wipe it clean with a slightly damp cloth or tact rag, let it dry or buff it dry with a dry cloth, then apply the next coat.
Thus, it's best to wait until all coats have been applied and dried before walking through the room. After that final coat, your floors should be off-limits for 24 hours. This is the only way to avoid any damage.
After applying the first coat, make sure the surface is completely dry before using the tack cloth in between coats. We recommend using the tack cloth in between all coats for the smoothest results. Once finished, if the tack cloth is full of particles, safely dispose.
Factors Influencing Polyurethane Drying and Curing Times
For a faster-drying wood floor finish, use water-based polyurethane, which takes six hours to dry before being ready for sanding and a second finish. An oil-based Polyurethane is going to take 24 hours before being ready for sanding or touching.
How do I actually sand a nib out of polyurethane? You can use the abrasives you're already using, but another tip you might like to try is to use the rough side of brown paper. This is just abrasive enough to take most nibs off without the risk of rubbing through the finish.
Sounds like the poly might have picked up some dust. Try "sanding" its surface with a piece of kraft paper (for example, a piece of a brown paper bag), which is just abrasive enough to polish the surface.
How to Apply Polyurethane: When working with any finish. Use natural bristle for oil-based finishes and synthetic filament (polyester, nylon, or a blend of the two) for water-based and water-based oil-modified finishes. Don't use rollers or foam brushes—they create bubbles.
One coat generally won't be thick enough to provide lasting protection, nor smooth enough. Many thinner coats result in a better finish that will generally dry better than fewer thicker coats. You can go more than three coats but the results may worsen if you go too many as it'll have that real plastic-y feel to it.
The dull and shiny spots in your hardwood floor indicate that your installers did not apply the finish correctly. Dull spots in polyurethane floors usually indicate that the finish was not applied carefully, the applicator had a dry spot on it, or the finish was thinned out with a solvent such as mineral spirits.
Water or Mineral Spirits - Removing Poly Dust from sanding between coats.
Can I use an orbital sander on polyurethane?
I have used an air-powered random orbit sander on a floor that I was pre-finishing with poly. Since I used no sealer, making the first coat of poly the sealer, it was fairly rough. I sanded with 150 grit, just making a couple of quick passes so it wouldn't sand through. It smoothed right out with no problems.
Thin your polyurethane with paint thinner, mixing it with a paint stir stick. When polyurethane is too thick, the brush marks hold their shape and don't settle out. Thinning the product provides a smoother finished surface. Experiment with different amounts of paint thinner to see what works best for you.
Can I Use Polyurethane on Bare Wood? Yes. If you prefer the look of bare wood, you do not need to use stain before applying polyurethane.
Is Polyurethane Waterproof? This finish protects your floors, but polyurethane is not waterproof. It will make your floors water-resistant, though — the coating repels water and helps prevent water absorption.
Get the highest-possible finish clarity— in a water base—with Rust-Oleum® Varathane® Crystal Clear Water-Based Polyurethane. Designed to let wood's natural beauty shine through, this formula provides maximum scratch and stain resistance on indoor furniture, doors, etc.
Apply 4 coats of oil based polyurethane on wood and wait 8 hours in between. Don't apply too many coat and you should be just fine.
Yes, Feed-N-Wax is compatible with all cured (fully dry) clear coat finishes including; tung oil finish, polyurethane finish, varnish, and lacquer wood finishes. Feed-N-Wax adds a protective coating of beeswax and carnauba wax that helps prolong the life of the finish.
If your stain is not fully dry, you run the risk of your first coat of finish not drying for days. Wait at least the amount of time recommended or more if the temp is low or the humidity is high. The first coat of finish does not bond to stained wood well if it's applied to soon after the wood is stained.
The polyurethane layer on top of the backing material can begin to break down, which can cause the material to become brittle and start peeling.
Open windows and doors. Use a fan to direct fresh air over the area. It can take up to seven days for the urethane to be 90 percent cured and 30 days to be cured completely. However, you should need the fan only for the first day, with periodic use after to remove buildup of fumes.
Do you have to sand floors between coats of polyurethane?
Polyurethane wood floor finish tips: Use 180 or 220 grit screen to sand in between coats. Wear down the screen with a piece of sandpaper before using it. This way it is not too aggressive and you will avoid heavy swirls.
It's one of the most durable coatings for wood protection against scratches, spills and more, and is a clear coat. It can be used on both finished and unfinished wood projects, and is available in a variety of sheens. The fast-drying formula allows for quick recoats in 4-6 hours.
The PU coating has extremely strong water-repellent characteristics and is even capable of making fabrics completely waterproof! Such a film can be applied once or multiple times. One coat is appropriately called single-coated, whilst multiple coatings are referred to as multicoated.
Depending on many factors, like your lifestyle and type of finish, polyurethane can last between three to six years. However, if you see damage on your floors, it may be time to reapply a fresh finish to your hardwood.
In general, I do not advise sleeping in your home after a polyurethane application, regardless of whether you are using an oil-based or water-based finish. The fumes from the polyurethane can be toxic and may cause eye and respiratory irritation.
It doesn't matter except if you're using water-based poly. If so, the water will rust the steel wool fibers that end up stuck in the pores of the wood and cause rust spots. I prefer steel wool because it lasts longer and conforms to whatever curves you are smoothing.
Synthetic and finer than silk, microfibers have a wide range of uses, from cleaning sensitive surfaces like eye glasses to detailing automotive finishes. And as it turns out, with the right weave, they are excellent at removing fine dust in the same manner as commercial tack cloths.
Best Practices for Storing Polyurethane Brush Between Coats
Use an appropriate solvent or mineral spirits to remove any excess polyurethane from the bristles. Rinse the brush with warm water and mild soap, ensuring that all traces of polyurethane are removed.
The best option is to use a varnish or lacquer to give the wood a high gloss finish. While varnish can be sprayed or brushed on, lacquer is best applied by simple spraying. Spraying makes the surface seem finer than painting as it doesn't leave any strokes behind.
Nobody wants to do all the work of refinishing and end up with bubbles in the finish. “The most common causes for bubbles are shaking the can and improper brush prep—you don't stick a brush into the finish without first soaking the bristles in mineral spirits, for oil-based polys, or in water, for water-based polys.
What is the best roller for polyurethane?
1/4" rollers work best with urethane since it goes down thin. 9" wide works fine while the 18" gets the job done faster and creates less chances to develop a roller mark.
It's all about adhesion. When you recoat after 2 hours you get a chemical bond between layers. If you let it go longer than that, you need to wait 24 hours so it's hard enough to sand and get a mechanical bond.
Apply the First Coat of Polyurethane
Spread the varnish over the entire surface with long, even strokes. Pro tip: Don't use too much or you're likely to get runs; use just enough to get a nice, even coat without dry spots. As soon as the surface is coated, brush over it again with the grain, from end to end.
- Angular sash: Slanted bristles that help with cutting-in and trim.
- Trim: A flat brush ideal for large, flat surfaces.
- Flat sash: Level bristles that help cover flat areas.
- Wall: Thick bristles that help you cover large surface areas in less time.
Generally, more than 3 coats of poly doesn't do much good. It's really not needed nor recommended. Each additional coat needs to be buffed so you are kind of buffing off half of the previous layer. So 4 coats is more like 3.5 coats.
Two coats of oil based Polyurethane are recommended on stairs. For added step protection and slip-resistance, opt for three coats, while water based polyurethane, you can apply four or more coats. Wait for at least 8 hours before reapplying oil-based Polyurethane and 2 hours for water-based polyurethane.
It doesn't matter except if you're using water-based poly. If so, the water will rust the steel wool fibers that end up stuck in the pores of the wood and cause rust spots. I prefer steel wool because it lasts longer and conforms to whatever curves you are smoothing.
I have used an air-powered random orbit sander on a floor that I was pre-finishing with poly. Since I used no sealer, making the first coat of poly the sealer, it was fairly rough. I sanded with 150 grit, just making a couple of quick passes so it wouldn't sand through. It smoothed right out with no problems.
If you put polyurethane on a rough surface you will get a rough finish. Second, as @keshlam says, make sure there is no dust at all on the surface before you apply the finish. A slightly damp cloth can help pick up anything remaining (but make sure the wood is dry before you apply).
It requires around 2 to 4 hours for a water-based polyurethane and 6 to 10 hours for an oil-based to cure and eventually be subject to a second coating. Figures as these still vary depending on the type of base, humidity ratio, air pressure, and even the state of the woodwork.