What are the best practices for polyurethane? (2024)

What are the best practices for polyurethane?

You'll get the best results from your polyurethane topcoat if you remove any old paint, varnish or other finishes before polyurethane application. For a smooth coating, you'll want the surface to be as smooth as possible. Prepare the wood by sanding it with a sanding block or orbital sander.

You'll get the best results from your polyurethane topcoat if you remove any old paint, varnish or other finishes before polyurethane application. For a smooth coating, you'll want the surface to be as smooth as possible. Prepare the wood by sanding it with a sanding block or orbital sander.

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.

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.

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.

Water-based polyurethane requires at least two hours of dry time between coats, and you should only apply two coats in a day.

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.

Let the finish cure – Cured finishes buff up better and faster than finishes that aren't fully cured. The longer you wait the better. Shellac, solvent and water-based lacquers and two part finishes should cure at least a week. Oil-based varnishes and polyurethane should cure at least two weeks.

I prefer to use a wipe-on poly because it goes on thinner and does not leave the brush marks. You could sand what you have to smooth it, then thin the poly about 50% and use it as a wipe-on. Using it as a wipe-on applies it in a thinner layer and with it thinner it will also dry faster.

Using steel wool or sand paper allows you to create a uniform surface for the next coat of polyurethane, which generally looks nicer, more professionally, etc. In my experience, assuming the finish is dry, there isn't a difference other than the coarseness of the sand paper or steel wool.

What are the disadvantages of polyurethane?

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.

It is recommended to use a high-quality synthetic brush instead of a natural one. You should also soak your brush with water to avoid your polyurethane from running or puddling. Doing so causes the bristles of your brush to stick together and removes any trapped air that can cause bubbles.

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.

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. Also, if you can swing it, hold off 3-7 days before moving furniture back into the room.

The average coating thickness for urethane is 0.032” to 0.058”.

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. But there are some caveats.

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.

An oil-based Polyurethane is going to take 24 hours before being ready for sanding or touching. Type of Wood: Aromatic cedars and Rosewood may result in drying and curing delays because their natural oils slow the process.

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.

How long after polyurethane can I walk?

It's recommended that you stay out of your home for at least 8 hours after applying a water-based polyurethane finish, though usually, you can walk on it much sooner. For a single-component water-based finish, full cure time is usually 7-14 days.

Apply 3 to 4 coats of water based polyurethane on wood wait 2 hours in between layers. 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.

This curing process can take 3-4 weeks depending on environmental conditions and how thick a film was applied. As long as it is emitting and odor, it's still curing. You can lightly sand with a 24 - 48 hour drying time. "Rubbing out" should not be attempted until the full cure time has elapsed.

Poly can be considered cured enough for light use (while still not being fully cured) when you can no longer smell any solvent odour with your nose pressed right against the surface. Expect this to take a few days to a week.

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.

*How Do I Remove Brush Strokes from the 3rd Coat of High Performance Polyurethane? Sand down the final finish with a 220-grit foam sanding pad, and then add another layer of General Finishes High Performance PolyurethaneTopcoat. Apply liberally than you did previously without heavy back-brushing.

The poly simply needs to cure for a while. Even after it "dries" and is safe to work on, the solvents that keep the polymers in suspension aren't all gone; they'll continue to evaporate, and the clear coat will fully harden in time. Check the can for your particular product; it should have a full cure time.

Polyurethane is so durable and water-resistant, it has largely replaced shellac and varnish as a wood finish. Originally, it had to be brushed on, but different formulations mean it can now be applied as a spray or by wiping it on with a rag.

The streaking you are describing seems to be the result of the finish being applied too thin. But you don't want to go quite as thick as a brushed-on coat. The way I get a coat that is “just right”, is by using the wipe on/no wipe off method. And I would abandon the sponge applicator in favor of a simple folded rag.

Yes. If you prefer the look of bare wood, you do not need to use stain before applying polyurethane.

Should I use a tack cloth between coats of polyurethane?

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.

[Sandpaper and steel wool are two different abrasives that will bring a different quality to the surface of a piece of wood or a finish. If I dare make such a comparison, 0000-steel wool is about equivalent to 400-grit sandpaper.]

But when it comes to applying a smooth coat of clear finish, such as polyurethane, a foam brush is not my first choice. Instead of bristles, it has a blade. The blunt sides leave two parallel ridges of finish, like a snowplow on the highway. Also, the foam head contains air, which can leave bubbles in your finish.

You should use an automotive polishing compound and a buffer for big areas. Small areas will have to be polished by hand unless you have some funky buffing tools. Make sure the poly has cured for a minimum of 4-5 days at 70f. Do not try to polish an uncured film.

Most clear finishes are applied with a brush, working in the direction of the grain of the wood. After it dries, sand lightly. Then remove all the sanding dust and apply a second coat. For added durability, a third coat can be applied.

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.

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.

Humidity and Temperature: Polyurethane dries faster in lower humidity and higher temperature. At increased temperatures, the polyurethane will dry faster, at lower temperatures it will take longer. A temperature of 70F and 50% humidity is what it takes for the average dry times mentioned above.