Polyurethane is today a very popular wood finish for home shop projects as well as professional woodworkers. Even though we at Obsessed Woodworking like shellac as an excellent wood finish, a subject we recently wrote about here, we also understand both the benefits of polyurethane and its ease of application.
When the wood has been well prepared, polyurethane will give your project a smooth finish, a hard film cover, great durability, and long-lasting protection for your project. By well-prepared, we mean:
- Smooth. You’ve taken your time with a high grit sandpaper, even a 320-grit sandpaper, to make the wood smooth before you begin finishing.
- Dust-free. After sanding, you’ve wiped the wood surface of all dust. You want the finish to be clean.
- Layers. You’ve sanded between coats, again with a high-grit sandpaper, and cleaned thoroughly after sanding before adding the next coat.
Following these steps will give you the finish your project deserves.
We’ve written a few times about polyurethanes, most recently here. As noted in that piece, polyurethane comes in both water-based and oil-based versions, and well-known brands for polyurethane include Minwax and Varathane.
Minwax water-based polyurethane is a clear coat film finish – it does not penetrate the wood; it merely forms a protective film on the wood surface – as opposed to an oil finish that sinks into the wood. It is a plastic that is applied to wood surfaces as a liquid that, when fully dry, is a solid plastic sheet. It provides a water-proof barrier for the wood, protecting it from its enemy – moisture.
Varathane polyurethane will also give your wood a clear coat film finish that provides excellent protection from scratches and stains. It, too, is a good choice for your indoor projects like furniture, cabinets, and trim.
- Protects indoor wood surfaces such as furniture, windows, cabinets, trim and more
- Water based formula dries fast and cleans up with soap and water
- Dries to the touch in 30 minutes with coverage up to 125 sq. ft., recoat after 2 hours
- Durable formula provides outstanding stain and scratch resistance with excellent clarity
Oil-based polyurethane, while also protecting wood from moisture, dries and cures with a slightly amber tone to wood over time. This distinguishes it from water-based polyurethane.
Minwax Polyshades is an oil-based, one-step stain and polyurethane product that gives you wood stain color and polyurethane protection. Minwax suggests the best way to apply it is using the tip of a natural bristle brush in a thin coat with long, smooth strokes.
Sanding lightly in between coats with very fine grit sandpaper will remove any bubbles and start/stop marks. Be sure to follow the steps outlined earlier, wiping all dust from the surface before applying a second or third coat (to deepen the color) in the same way as the first.
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- Recommended uses: furniture, woodwork, doors, cabinets, accessories
- Stain and polyurethane in on easy step
One other “thane” to mention is spar urethane. It is for both interior and exterior use and is formulated to provide further protection to changing environmental conditions. The sun’s UV rays, like water, are wood’s enemy, and changing temperatures are the third on that enemy list.
Spar urethane is a more water-resistant finish than polyurethane and can be applied in higher moisture conditions. It also contains UV blockers to protect the wood from harmful sunshine.
As between the two, Varathane and Minwax, and while many consider Varathane to be more easily applied and with a faster drying time, Minwax is the less expensive option while still providing strong protection for your wood surface.
Now that we’re talking about applying polyurethane let’s get to the how of its use.
When originally developed, polyurethane had to be applied by brush. But as formulations evolved, it became possible to apply it either by spray or by wiping it on with a cloth. Additionally, mineral spirits can be mixed into polyurethane to thin it for a more forgiving coating – the mineral spirits will help break up any air bubbles in the coat before it dries.
A good ratio would be 3 parts polyurethane to 1 part mineral spirits. But, be sure to stir it slowly and softly, and never shake it so that you aren’t forcing additional air into it that will form bubbles.
In fact, you can now buy polyurethane that has been pre-thinned with mineral spirits. This Wipe-on Poly, as it is called, comes from Minwax and is ready for use right out of the can.
While Minwax suggests a heavy coat be applied, allowed to dry for 3 hours, and lightly sanded with a fine grit sandpaper, many other woodworkers suggest instead 3 thin coats for a smoother appearance. They also suggest not sanding the first coat, as you might sand through it; instead, allow the first coat to dry thoroughly, apply the second coat, and after it has dried completely, then lightly sand with a fine grit sandpaper.
Repeat this for the 3rd coat to achieve that smooth appearance.
Here’s an informative video devoted to using a Wipe-on Poly.
What Kind Of Rag Should You Use?
The advantages of using a rag or cloth to apply polyurethane are ease of application and avoidance of drips and brush marks without streaks. Thinning the polyurethane with mineral spirits helps avoid bubbles. Together, they make the finishing of your project easy and effective.
Pour some onto a clean, white, lint-free rag or cloth, or put some into a smaller container and dip the rag or cloth into it. Apply to the wood surface by wiping in smooth, even strokes, overlapping each stroke with the previous one to ensure a full and even coating. You can also use a microfiber cloth to apply a polyurethane finish.
The fellow in this video uses a 50/50 polyurethane/mineral spirits blend but otherwise has some helpful tips for applying it with a rag.
While polyurethane is non-carcinogenic and is not absorbed by the skin, it’s prudent to wear gloves when applying it with a cloth. It will make cleaning up easier for you.
Avoiding bubbles, brush strokes, and streaks in the application, are good reasons to choose this method for finishing your project. Follow the three steps we outlined at the beginning of this article – – smooth, dust-free, and layers – and that project you worked so hard and well to complete with have a protective and smooth finish befitting your efforts.
Last update on 2023-02-05 / Affiliate links / Images from Amazon Product Advertising API