Does Polyurethane Fade Over Time? What Tests Show

Polyurethane can fade over time due to exposure to sunlight, UV radiation, oxidation, temperature, and humidity. Changes in color, glossiness, and texture are common signs of fading. However, applying a UV-protective coating, maintaining proper humidity levels, and applying a maintenance coat can help prevent and fix fading.

After years of playing around with polyurethane finishes for hundreds of outdoor projects, here’s what we found.

What Causes Polyurethane to Fade Over Time?

Many often choose polyurethane since it is a durable wood finish that can withstand wear and tear.

But, despite its many advantages, poly finishes can still lose their shine and protective characteristics over time.

A range of factors can cause this to happen, including exposure to sunlight, UV radiation, oxidation, temperature fluctuations, and changes in humidity.

Exposure to Sunlight and UV Radiation

Polyurethane-coated wood in sunlight
Polyurethane-coated wood in sunlight

Sunlight can harm polyurethane, causing it to fade and lose its shine over time.

Direct exposure to sunlight for extended periods can result in a lackluster and dull finish.

This happens as the polyurethane breaks down under the sun’s influence, losing color and glossiness.

UV rays can penetrate the finish, causing the wood to darken or lose its original color, leaving it vulnerable to damage.


Another reason polyurethane can fade is due to oxidation.

As the finish is exposed to air over time, it can break down, losing color and glossiness.

Oxidation is particularly common in polyurethane finishes subjected to high temperatures or direct sunlight.

Temperature Changes

Temperature fluctuations can also cause polyurethane to fade as the finish may expand or contract under extreme heat or cold, resulting in cracking or flaking.

Temperature changes can also compromise the protective properties of the polyurethane, leaving the wood more prone to damage.

Humidity Changes

Water droplets on a polyurethane-coated wood surface
Water droplets on a polyurethane-coated wood surface

Humidity changes can also contribute to polyurethane fading.

High humidity levels can cause the finish to absorb moisture, leading to swelling and cracking.

On the other hand, low humidity can cause the polyurethane to dry out, losing color and glossiness.

Signs of a Fading Polyurethane

If you suspect your polyurethane finish is fading, there are several signs to look for.

Changes in color, glossiness, and texture indicate that the finish is starting to fade.

Changes in Color

Dark spots on polyurethane due to changes in color
Dark spots on polyurethane due to changes in color

When polyurethane fades, it can cause the wood to lose its natural color.

Depending on the degree of fading, the finish may appear lighter or darker than its original shade.

Changes in Glossiness

Polyurethane fading can also result in losing the wood’s glossy finish.

The finish can appear lackluster or dull and may no longer reflect light as it did previously.

Changes in Texture

Polyurethane fading can make the wood feel rough or uneven to the touch as the layers start to break down.

These signs can be easily noticed and indicate that your polyurethane finish is fading.

Remember, you can always sand the surface and apply a new coat of poly to restore the original texture.

Techniques to Prevent Polyurethane from Fading

Preventing polyurethane from fading is essential to maintaining the beauty and longevity of your wood finish.

Here are some effective ways to prevent polyurethane from fading:

Applying a UV-Protective Coating

Applying a UV-protective coating is recommended to keep polyurethane from fading.

It acts as a barrier against UV rays, preventing them from entering the finish and causing fading.

It is essential to find a coating suitable for use on polyurethane finishes and follow the application instructions provided by the manufacturer.

Storing Wood in a Cool, Dry Place

Storing the wood in a cool and dry location is recommended to prevent polyurethane from fading.

The finish can break down and fade when exposed to extreme temperatures and humidity.

If feasible, storing the wood in a climate-controlled area, away from direct sunlight, can help preserve its finish.

Avoiding Direct Sunlight

Polyurethane-coated wood exposed to direct sunlight
Polyurethane-coated wood exposed to direct sunlight

Exposure to direct sunlight is one of the primary reasons for polyurethane fading, and limiting wood exposure to it is vital.

Consider relocating furniture or objects in direct sunlight to a different location or using a protective covering to block the sun’s rays.

Maintaining Proper Humidity Levels

Proper humidity levels are crucial to avoid polyurethane fading.

The fluctuation of humidity levels can cause the finish to expand and contract, leading to cracking and fading over time.

Using a humidifier or dehumidifier is recommended to maintain consistent humidity levels in your home and prevent damage to the wood’s finish.

Applying a Maintenance Coat

To prevent polyurethane from fading, you can regularly apply a maintenance coat.

A maintenance coat is a thin layer of polyurethane applied to the surface of the existing finish to provide an extra layer of protection.

It’s important to follow the manufacturer’s instructions for application and allow the coat to dry completely before using the wood.

This simple step can help prolong the life of your polyurethane finish and keep your wood looking its best.

Ways to Fix Fading Polyurethane

If your polyurethane finish has already started to fade, there are several ways to fix the problem:


Sanding the polyurethane-coated wood Surface
Sanding the polyurethane-coated wood Surface

If you have faded polyurethane, sanding the surface can restore its color and glossiness.

Sanding with fine-grit sandpaper can remove the top layer of the finish and reveal a fresh layer underneath.

Make sure to sand in the direction of the wood grain to avoid causing any further damage (learn to remove polyurethane without sanding).


Removing polyurethane by scraping
Removing polyurethane by scraping

If sanding doesn’t remove the faded polyurethane, you may have to strip off the entire finish and begin anew.


Applying oil-based polyurethane
Applying oil-based polyurethane

Once you have sanded or stripped the faded polyurethane from your wood, you can apply a fresh coat of polyurethane to restore its original beauty.

Applying thin and even layers of poly finish yields better results.

Allow the finish to dry completely before using the wood to ensure the new coat is fully cured and ready to protect the surface.

Final Thoughts

Polyurethane fading can be frustrating, but it is a common problem that can be prevented and fixed.

You can do a few things to prevent fading, such as using a UV-protective coating, storing wood in a cool and dry place, avoiding direct sunlight, maintaining proper humidity levels, and applying a maintenance coat.

These measures can help keep your wood finish looking great for a long time.

But if your polyurethane finish does fade, you can fix it by sanding or stripping it and then reapplying a fresh coat of polyurethane, following the manufacturer’s instructions for the best results.

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Frequently Asked Questions

Does polyurethane finish age?

Yes, polyurethane finish can age over time. Exposure to various elements such as sunlight, heat, humidity, and regular wear and tear can cause the finish to fade, lose its glossiness, and even crack or peel. However, proper maintenance, including applying a maintenance coat and avoiding direct sunlight, can help slow aging.

How long does polyurethane take to dry

Polyurethane can take 4 to 48 hours to dry, depending on humidity, temperature, and the type of polyurethane used. It is important to allow the finish to dry completely before handling or using the surface to avoid damaging the finish.

How to tell if polyurethane is bad?

When polyurethane goes bad, it can become thick, stringy, or have a foul odor. Another sign is if it has hardened in the container or if a layer of film is on the surface. If you notice any of these signs, it is best to dispose of the polyurethane and purchase a new one.