Polyurethane and PolyShades are both popular wood finishes that provide protection and enhance the look of wood surfaces. Polyurethane is a clear finish that comes in gloss, semi-gloss and satin sheens. PolyShades is a unique product that combines stain and polyurethane in one step, providing both color and protection for wood. A common question many DIYers have is whether you can apply PolyShades over an existing polyurethane finish. The short answer is yes, you can apply PolyShades over polyurethane, but there are some important factors to consider first.
Preparing the Surface
Before applying PolyShades over polyurethane, proper surface preparation is essential. The existing polyurethane finish must be completely cured and free of wax, grease or other contaminants. Lightly sand the surface with 220-grit sandpaper to rough up the finish and allow the PolyShades to adhere properly. Be sure to remove all dust after sanding. For best results, use a tack cloth to pick up any remaining dust or debris. This helps create a smooth finish.
Test First
It’s always a good idea to test the PolyShades on a inconspicuous area first, like underneath a table or on a closet shelf. This allows you to check compatibility and makes sure you like the final color result. Keep in mind that applying PolyShades over polyurethane will create a slightly different color than applying it directly to raw wood. The original polyurethane tint will influence the final color. Do a test area to make sure you’re happy with the color before proceeding.
Applying PolyShades
When applying PolyShades over polyurethane, follow the manufacturer’s instructions carefully. Use a good quality natural bristle brush and maintain a wet edge as you apply. Applying a thin coat of PolyShades and allowing it to fully cure creates the most durable finish. Most products recommend 2-3 thin coats for best protection and color depth. Lightly sand with 220-grit sandpaper between coats to smooth the finish.
Work in sections, applying PolyShades across the wood grain. Use smooth, even brush strokes and avoid over-brushing. Allow the PolyShades to cure fully, checking the manufacturer’s recommended recoat time before adding another layer. Proper curing produces a harder, more durable finish.
Considerations
Here are some important factors to keep in mind when applying Minwax Polyshades over an existing polyurethane finish:
- Adhesion – PolyShades bonds best when applied directly to raw wood. Adhesion over polyurethane may be reduced, especially if the previous finish was improperly cured. Proper prep helps improve adhesion.
- Incompatible finishes – Oil-based polyurethane and PolyShades are compatible. However, PolyShades will not bond well to waxy finishes like tung oil or lacquer finishes. Make sure you know what base finish is currently on the wood.
- Existing finish color – The original polyurethane finish will influence the final PolyShades color. The base color tends to mute PolyShades color. Test first to ensure you like the final colored result.
- Cure time – Allow more cure time when applying PolyShades over polyurethane. The previous finish can slow the curing process. Allow double the recoat time before adding another layer.
- Sanding – PolyShades cures to a hard film finish. In between coats, sand lightly with 220-grit sandpaper. Avoid aggressive sanding that removes previous finish layers.
Advantages
While directly applying Polyshades to raw wood is ideal, there are some advantages to applying it over an existing polyurethane finish:
- Enhances color – PolyShades adds rich color onto an existing clear finish. It allows you to re-stain the wood without having to completely strip and refinish.
- Quick update – Applying PolyShades over polyurethane allows you to quickly change the color of a finished surface without completely redoing it.
- Added protection – The PolyShades adds another protective layer, increasing the durability and lifespan of the finish.
- Easier cleanup – With an existing base finish, Polyshades can wipe up easier with minimal staining to surrounding surfaces.
Disadvantages
There are also some potential disadvantages to consider when using Polyshades over polyurethane:
- Adhesion issues – PolyShades may not bond as well to a slick polyurethane surface, leading to possible delamination or finish failure.
- Inconsistent coloring – The original finish color affects the PolyShades, often creating a muddy or uneven final color.
- Longer curing time – Applying PolyShades over polyurethane slows the curing process, requiring a longer time between coats.
- Streaking – Over-brushing or applying PolyShades too thick over polyurethane can create streaks in the final finish.
- Bubbling – Trapped air bubbles are more likely to occur when applying PolyShades to a non-porous surface.
Best Practices
To achieve the best results when applying PolyShades over an existing polyurethane finish, keep these best practices in mind:
- Proper prep – Lightly sand and clean the surface so PolyShades can bond successfully.
- Thin coats – Use a foam brush to apply thin, even coats of PolyShades. Allow proper curing time between coats.
- Across the grain – Brush PolyShades across the wood grain to help minimize streaking.
- Test first – Do a test spot to ensure proper adhesion and check the resulting color.
- Patience – Additional cure time is required when applying over polyurethane. Don’t rush the process.
FAQs
Here are answers to some frequently asked questions about using Minwax Polyshades over polyurethane:
| Question | Answer |
|---|---|
| How long do you have to wait before applying Polyshades over polyurethane? | Wait at least 2 weeks for the polyurethane to fully cure. Lightly sand and wipe clean before applying PolyShades. |
| Can you put oil-based Polyshades over water-based polyurethane? | No, you should not mix water and oil-based finishes. Use an oil-based PolyShades if the existing finish is polyurethane. |
| How many coats of PolyShades should you apply over polyurethane? | 2-3 thin coats of PolyShades are recommended over an existing finish. Allow proper curing between coats. |
| Will PolyShades adhere to polyurethane? | PolyShades will adhere to polyurethane but the bond is not as strong as applying directly to raw wood. Proper prep helps improve adhesion. |
| Can PolyShades go over semi-gloss polyurethane? | Yes, PolyShades can be applied over any polyurethane sheen including semi-gloss. Scuff sand first before applying. |
Conclusion
Applying Minwax Polyshades over an existing polyurethane finish is possible with proper preparation and technique. Lightly sanding and cleaning the polyurethane allows the Polyshades to bond adequately. Using thin, even coats across the wood grain helps produce an attractive, uniform finish. Allowing longer cure times between coats prevents sagging or running. While applying PolyShades directly to raw wood is best for maximum adhesion, with some care it can also be successfully applied over cured polyurethane finishes.
Test first on a sample area to check compatibility and color results. Patience is important, as additional coats and cure time will be required. Following the manufacturer’s recommendations for surface prep, application and recoat times produces the best results. With some simple preparation and best practices, Minwax PolyShades can enhance the color and provide extra protection over an existing polyurethane finished surface.