Frequently, many people get so frustrated after going through the task of coating, only to end up having cloudy finishes. Cloudy polyurethane finish appears as a result of moisture build-up and not thoroughly stirring the product before application.
Perhaps you might have tried different methods and strategies to fix your cloudy finish. However, still no effect, probably it only worsened the surface.
Polyurethane is a polymeric resin, with its characteristic hard, robust varnish applied on another surface to bond tightly with it. As the polyurethane dries, the surface becomes tightly bonded, giving off a finish that’s resistant to wear, abrasions, and impact. Polyurethane is added to surfaces to increase their efficiency and durability.
All at a Glance
Types of Polyurethane
To know the different types of polyurethane finish that suits your project, you need to be conversant with the types and their specifications to know the one most suitable for your desired surface.
There are two types of polyurethane which are:
- oil-based polyurethane
- Water-based polyurethane.
Oil-based poly turns into an amber or yellow finish once applied. They form a hard, thick covering in a few coats, but they dry slowly, which means you will have to wait in between each coat to dry before applying another. Oil-based polyurethane takes about 24 hours to dry, after which you can work on it freely without having to worry if it’s cured or not.
However, they are not cured totally, which means you have to tread gently while dealing with the surface.
Before applying the polyurethane, ensure you keep your pets and furniture away, as they can meddle with the polyurethane drying time.
Water-based polyurethane dries more quickly than oil-based formulas, but it’s always more watery. This means that you will have to apply more coats, probably up to three, unlike an oil-based finish that needs fewer coatings.
Water-based polyurethane typically dries after six hours of application. At this point, the surface must have become dry and ready to use. Again, it’s not completely cured, which means you’ll have to handle the surface gently and would care.
How to fix cloudy polyurethane finish before curing
Polyurethane finish doesn’t usually end up blushing but can turn milky as time goes on or when it comes in prolonged contact with something wet. Lightly sand the finish with a 220- grit sandpaper, clean the sanding dust with a rag and spray a full wet coat. Allow it to dry.
How to fix a cloudy polyurethane finish after curing
To remove cloudy marks from a cured polyurethane finish, first off, spread a thick coat of lemon oil or petroleum jelly on the affected surface area and leave it for approximately 24hours.
Both lemon oil and petroleum jelly have a more significant attraction for the oil-based finish when compared to water, which makes them soak in to replace trapped in moisture. After applying the oil or petroleum jelly for 24hours, wipe off the excess and allow the material remaining to dry.
After drying, warm the finish slowly using a blow-dryer or lamp. Using these alternatives will make the finish soften and eventually reconstitute itself but be careful not to overheat the finish. This might damage the surface you’re trying to repair.
It shouldn’t be too hot to touch. Rub the cloudy areas with a clean cloth moistened with alcohol. Alcohol functions so that it absorbs moisture use a small amount of alcohol and force while applying to avoid damage.
The cloudy spots on the surface won’t come out frequently since it is cured, and the only option left is to strip the surface of its previous finish to apply a new one.
What causes cloudy polyurethane finish? There are a lot of factors that cause a cloudy polyurethane finish, some of which are:
- The old finish applied over a wood surface
- Storage of polyurethane in an extremely hot or cold place
- Finish applied on an unclean surface
- Oil over the surface.
- Not following the manufacturer’s directions.
- Not stirring enough before applying
- The build-up of moisture.
Steps on how to fix a cloudy polyurethane finish.
Cloudy finishes on surfaces appear due to various reasons, which include using an old product stored in a very cold or hot environment, not stirring well before application, not following the label instructions, amongst others.
This tampers with the initial purpose of using the poly finish in the first instance, but you need not worry as these steps will help guide you on how to fix the cloudy polyurethane finish.
Step 1: Test the finished surface in case you don’t know what type it is. Check to see if it is a curing or non-curing finish. Rub a part of the wood surface with a rag dipped in denatured alcohol. If it doesn’t soften, then it’s a polyurethane finish.
Step 2: in case the surface has been waxed, clean it with detergent and water.
Step 3: get 220-grit sandpaper and lubricate with mineral oil or water and then stand out surface defects and errors such as cracks, bubbles. After the surface is leveled, spread a fresh coat of polyurethane evenly with a brush or spray it.
Always make sure the polyurethane finish is thoroughly stirred before you apply it to your desired surface. This reduces the chances of your wood surface getting cloudy.
Step 4: mend drips in the poly finish by sanding them out with a lubricated sheet of 220-grit wet or dry sandpaper. Then apply more finish when the drips are leveled out.
Tips on how to fix a cloudy polyurethane finish
- Check: check if the polyurethane is completely dry, especially if you just refinished the piece recently.
- Clear: clear out the working area, turn off any open flame.
- Use of mineral spirits: Pour a little amount of mineral spirit into a clean, soft finishing sponge, cover the sponge with a white cotton cloth, twist the top part of the cloth to form a handle.
- Rub and dry: Rub the wrapped sponge in a back and forth motion on the finish to remove the first coat. Allow it to dry, and use the sponge to rub over the surface again. Repeat the process until the cloudy appearance disappears. Then allow it to dry completely.
- Sand: Gently sand the surface with 220-grit sandpaper to remove all the cloudy polyurethane finish. Sand until all the polyurethane finish is removed, reapply the finish following the product instructions, and stirring it as you work and before applying.
Materials and equipment needed
- Finishing sponge
- Mineral spirits
- Clean cotton rags
- 220- grit sandpaper
- Lemon oil
- Petroleum jelly
How to Apply Polyurethane Over a Painted Surface
First off, you need to determine whether you want an oil-based or water-based polyurethane. I advise that you opt for a water-based polyurethane to avoid amber coloring. If you’re looking to protect the paint and add beauty to the painted surface, you should consider applying two or more coats.
This will boost the surface resistance and strength. Remember, you can apply polyurethane to any paint. All you have to do is allow the paint to dry correctly (if it’s recently painted), clean the surface, and prepare it for application.
Step 1: Wash the Surface
If the surface has been long painted, you should begin by washing it properly. Washing it will take away the grease, stains, dirt, and all types of dirtiness, which is vital to maintain a clean surface. To clean, use a soft sponge and a powerful detergent to clean the area.
Alternatively, you can mix one-half cup of trisodium phosphate in warm water to clean the surface. Trisodium phosphate is known for its cleaning ability making it the choice for most painters to get painted surfaces clean.
Step 2: Get the Scuffs Off
Allow the painted surface to dry adequately after washing. This usually takes between 24 and 72 hours. After drying, use 120-grit sandpaper to sand off the surface. Doing this will prevent any deep scratches from forming, and it helps to flatten the surface.
If you don’t sandpaper the surface, you will notice some uneven surfaces and deep scratches under it after applying the polyurethane. You can choose to flatten the surface by hand or a palm sander. When you are done, wipe clean the dust with a damp cloth.
Step 3: Choose Your Applicator
After you must have chosen your polyurethane type, next is to select your method of application. Avoid using a roller to apply the polyurethane because it will leave bubbles behind. For best application, you should either use a brush or sprayer.
Brushing works best when working on a flat surface that requires building a strong or thick film. Spraying works best for hard to reach surfaces.
However, the film isn’t as strong or thick as that produced when you brush the surface. You can also apply polyurethane by wiping.
This method is best for contoured surfaces like crown molding. The process forms a thinner coat. Ensure that the surface you want to use for this method is not wear-prone.
Step 4: Apply the First Coat
After applying the first coat, allow it to dry for a while. Once it’s scorched, begin to scuff off the surface with sandpaper to remove any dust particles and achieve a flattened surface.
Step 5: Apply the second coat.
Once the surface is dry and you’ve scuffed the surface, it’s time to apply the second coat. Most times, you’ll not need to use more than two coats. After applying the second coat, allow it to dry for at least 24 hours.
Conclusion- How to Fix a Cloudy Polyurethane Finish
So far, this article has shown various steps, methods, and tips on how to fix a cloudy polyurethane finish. Applying your poly finish might have always ended up in bubbles and cloudy results. Having a perfect polyurethane finish is not a big Herculean task for you.
All you have to do is follow the necessary guidelines, and your excellent polyurethane finish will look better when next you coat it.