The oil-based polyurethane varnish shines and brings out the best qualities of the wood it is spraying. However, it is one of the most difficult types of varnish to apply.
In this video, watch Darbin Notes who how to spray polyurethane for faster, mess-free coverage on your next wood project.
How To Spray Polyurethane Like A Pro
Below youll find a summary of the essential steps and then you will know how to spray polyurethane like a professional in no time at all.
It is important to have patience, discipline, and work in an area with good ventilation and no dust. Polyurethane has a strong smell and ventilation is important for you to work in a comfortable environment
Proper Sanding Is Essential
No matter the type of varnish, a smooth surface is required for it to look good. Sand the wood’s surface with progressively finer grades of sandpaper. Start with a 100-grit sandpaper. Next, use a 150-grit sandpaper. Finally, use the fine 220-grit.
Sanding Sequence
- For the initial sanding, start with 100 grit sandpaper
- Move to 150 grit or sand once more
- Finish by finishing with 220 or more fine gritsandpaper
After you have finished sanding the surface, be sure to inspect it for scratches or blemishes caused by coarser grits. Once satisfied with the smoothness of the wood, then you can wipe the surface with a tack cloth, to clean it of all traces of dust or trapped insects and grime.
Simple Spraying Techniques
- Spray at a constant angle and not an arc rotation
- Overlap slightly, like painting with a brush
- Spray a light coat better less than more to avoid drips
- Wait 48 hours between multiple coats
Spattering is one of the most common blemishes that you find when polyurethane is applied improperly.
The HVLP sprayer is a good example. Large drops of varnish are emitted from the sprayer before the fine spray. These can cause unsightly spatters. Spraying must begin before reaching the wood’s edge. Continue spraying until you reach the end. This will allow you to apply the fine spray to the wood and to sweep away any stray particles from your workspace.
Getting The Spray Angle Right
Spraying in an arc is the best way to get the best results, but many people mistakenly believe this. When you spray in an arc, you get more coverage at the center of the surface and less at the edges. The can must be moved at the same angle as the surface of the wood. Instead of swinging the can with your arm, move your entire arm.
In order to get a good, even coverage, you have to overlap the spray pattern just like you would if you were using a brush. The overlap should spread to at least halfway over the previously sprayed section. This will ensure that there is not a lot of debris at the edges. If you overlap 50% or more, you will get an even finish.
To build even coats, ensure that the tip of your spray can is at an equal distance from the surface of your project. Also, make sure to move the can at an equally fast speed. As a rule of thumb, you just need to spray enough polyurethane to wet the surface of the wood. This prevents the formation of run. It is better to spray several thin coats than thick ones, as these can lead to the formation and growth of runs.
When you have a large project, your finger may end up getting sore and tired, and this may lead to some uneven spraying patters. You can use all of your fingers by purchasing a spray handle at the local store. Using such a handle gives you better control over the spraying and saves your finger.
Dont Try To Cover In One Coat
If you have stains on the wood, you should first use a mist coat, rather than try to cover it up with a thicker layer of polyurethane. The solvent used to thin the polyurethane in the aerosol container can dissolve the stain, and this will bleed and make the project look murky. You can gently remove any blemishes or runs by using a razor blade. However, be careful not to make any deep cuts.
You should also wet-sand the surface to ensure that even the most minuscule of bumps has been removed; use a fine 220-grit sandpaper. You should wait at least 48 hours before applying the final coat. Polish the surface for another 48 hours.
