Why does my polyurethane look splotchy?

June 2024 · 6 minute read

Streaking Polyurethane Finish

Those streaking marks appear because polyurethane finish dries before marks are gone. This causes rapid gloss levels all over the surface. You may notice some areas have high gloss while some are not. This is a common mistake when using a water-based polyurethane finish.

How do you fix blotchy polyurethane?

Apply a very light coat of polyurethane to the sanded area with a brush. Allow it to dry and then check the evenness of the coat. If the coat remains too thick, re-sand the area and reapply polyurethane. If the coat is too thin, repeat this step until you have an even coat.

Why does my polyurethane look cloudy?

Before getting upset, check whether the polyurethane has actually dried. If you're using water-based material, it's common for it to appear milky before it dries. The color comes from the emulsion that carries the resins. If the finish is still wet, just wait -- the milkiness should disappear.

Why does my polyurethane look cloudy after sanding?

Cloudy finishes appear for several reasons, including using an old product or one that's been stored in a very cold or hot environment. Proper application also requires stirring the polyurethane coating immediately before placing it on the surface, which should be clean and oil-free.

Can you buff out polyurethane?

Add a pea-sized amount of car paste wax to a polishing pad or cloth. Work in short, smooth motions until there are no visible scratches in the polyurethane. Move the pad in smooth, horizontal motions so you can apply an even coat of wax to the surface. You can also use a section of 0000 steel wool to buff the surface.

Fixing Polyurethane Bubbles, Puddles, Runs and Brush marks

Should you sand between coats of polyurethane?

Yes. Minwax Polyurethane should be sanded between coats. Sand with 320 grit sandpaper to get rid of any fine particles of dust that have settled on it while it was still wet. Sanding in this case not only allows for a smoother finish but can also help abrade the surface and increase inter-coat adhesion.

Is it necessary to sand between coats of polyurethane?

MYTH #7: Scuff sand between coats to get a good bond.

The purpose of this instruction is to create scratches in the surface so the next coat of finish can establish a “mechanical” bond. The finish “keys” or “locks” into the sanding scratches.

Why does my polyurethane look uneven?

Uneven Polyurethane Finish

Contaminated polyurethane. Improper sanding and cleaning the surface. Uneven application of polyurethane finish.

Will polyurethane even out?

Definitely, YES! And there are two ways on how to get a smooth polyurethane finish through sanding. Dry sanding the final coat, which is what most people are familiar with.

Do you sand after last coat of polyurethane?

Sand lightly with 240-grit sandpaper between coats, then let the last coat dry for at least 24 hours. This is standard practice with any wood finishing job, and is nothing out of the ordinary. That said, sanding bare wood beforehand to create a smooth foundation is key.

Can you put too many coats of polyurethane?

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.

How long should you wait between coats of polyurethane?

If you use water-based polyurethane, you only have to wait between 2 to 4 hours before applying the next coat. However, when using oil-based polyurethane, you might wait for 10 to 24 hours. You can apply the next coat in as little as 4 hours if you are using fast-drying, oil-based polyurethane.

What grit sandpaper should I use for polyurethane?

Start with 120-grit sandpaper on refinished pieces and 80-grit on new wood. After sanding the entire surface thoroughly, wipe off the dust and all loose sandpaper grit with a clean cloth. Then, sand with 180-grit until you've removed all the marks left by the 120-grit, and the surface appears level.

Is it better to brush or roll polyurethane?

Don't use rollers or foam brushes—they create bubbles. Your brush will be easier to clean, and will go longer between cleanings, if its bristles are dipped first in mineral spirits, if you're using an oil-based poly, or in water, if the finish is water-based.

Should I sand after first coat of polyurethane?

Sand the dried and cured first coat of polyurethane no sooner than 24 hours after applying it. Use a very fine-grit abrasive, sanding with the grain of the wood. Remove the sanding dust first with a static duster, followed by a tack cloth.

How long does polyurethane take to cure?

It takes a full 30 days for the floors to cure, so it's ideal to wait 30 days before putting area rugs on the surface. If you need to/want to put them on sooner, then 2 weeks is another good benchmark, but 30 days is better.

Can you buff polyurethane with steel wool?

Saturate a piece of #0000 steel wool with lemon oil or mineral oil. Apply the oil to the piece by wiping over it with the oil-saturated steel wool, using light pressure. Let the oil dry and soak in for 30 minutes and then wipe off the excess with a clean, soft cloth or paper towels.

How many coats of polyurethane do I need for a smooth finish?

For best results, apply at least two coats of polyurethane. When working on floors, tables, chairs, and furniture that will be used often, apply at least three coats. If you are using water-based polyurethane, you can apply up to four or five coats on floors and sheds.

Do you sand between coats of clear coat?

Sanding between layers of clearcoat is also not recommended. Wet sanding and polishing the final layer will yield a better result than doing it between each coat. Clearcoat layers are also thinner than they look.

How do you apply polyurethane without brush marks?

When the brush marks don't resolve themselves, try a few corrective techniques.

  • Use a foam brush or a lambswool applicator instead of a brush. ...
  • Use a natural-bristle brush rather than a synthetic one if you are using a bristle brush. ...
  • Thin your polyurethane with paint thinner, mixing it with a paint stir stick.
  • Can you buff out brush strokes in polyurethane?

    *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.

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