How to Spray Polyurethane

If you are looking for an excellent finish for your wood or flooring, one of the go-to options is the Polyurethane.

It is one of the most favored materials to cover wooden surfaces as it gives hard gloss finish and is very durable. It is also very versatile as it can be applied to other surfaces.

There are many kinds of this substance in the market. The use of each type differs from the other.

So it is essential for you to understand the characteristics of each kind so spraying will be comfortable and practical.

Water Based vs. Oil-Based

man spray painting a ceiling

One of the factors to consider first before applying this varnish is knowing its base. The base affects the quality of your finished project. What are the differences between a water-based and an oil-based one?

Both a durable and create an attractive finish to the finished surface. However, they also have distinct features such as the following:

Finished coat

The most apparent difference between the water-based and the oil based one is the finished coating or the appearance. The water-based creates the natural and bright look of maple.

On the other hand, if you prefer to have an amber glow on your wooden floor, go for the oil based. In just one coating it already creates that accent.   

Drying time

Another critical factor to consider is the drying time of each material.

The water-based substance takes a less time to dry. In fact, you may only need two hours, and you can already apply a second coat.

On the other hand, the oil-based ones may take five to twelve hours to dry, which is a long time. Because of this, you will also bear with the strong odor for a longer time.


In connection to drying time, the need for touch-ups also differs between the water-based and the oil-based ones.

Water-based materials have only 30 to 35 solid percent of solids. Because of this, you may need to do more than two touchups to achieve a good finish. 

Meanwhile, the oil-based instantly gives you an amber glow even on the first coat. This is because the oil based has 45 to 50 percent solids. 


The varnish based on the water lasts for a long time as compared to the oil-based ones. This is because as mentioned earlier, water-based substance require more coats than oil base. Hence, the oil-based ones will fade soon.


Regarding cost, the water-based materials are the most expensive compared to the oil-based ones.

Getting Started

spray painting wood table

Before anything else, prepare the proper tools and materials for you to start your project.

  • Polyurethane
  • Roller tray
  • Rags
  • Floor finish applicator
  • Knee pads
  • Brush with a fine bristle and a foam brush (if you are going to use oil based material)

How to Spray Polyurethane Paint?

Get the work area ready for work.

First and foremost, you need to set up the work area. See to it that the work area is clean and as much as possible, free from dust, insects, etc. This is to avoid unnecessary substances/materials from sticking on your project surface.

It is also worthy to keep all materials and tools needed near you so your work will not get interrupted along the way.

Setting up the surface

Now that you are done getting your work area ready for work, set up the surface which you need to spray.

Same with your work area, make sure you target surface is squeaky clean and free from unnecessary materials or dirt. 

Before starting spraying, wipe the surface with a clean cloth to clear up any dirt and dust. This will help you achieve that smooth and flawless finish.  

Pre-spray preparations

Before you start spraying your target surface, prepare the materials you need. This kind of varnish needs thicker coats, and because of this, you might need the help of thinner.

Try doing the first spray and see if the finish enough. If it is still too thick, add thinner to the solution.


Sanding is very important in every painting project, especially if you are going to spray on a rough or an uneven surface.

To avoid bumps, it is advisable for you to sand the surface before starting spraying. You may use 100-grit sandpaper to 150-grit.


After preparing your work area, the target surface, and the materials, you are now ready to spray. For you to attain a good finish, spray the paint in thinner coats.

There are sprayers which are designed with controls to regulate the air pressure and amount of paint released.

Start with low pressure so it will be more comfortable for you to control the painting. 

Moreover, you might want to consider using sprayers with smaller nozzles or air assist tip sizes. This is to maintain the coating of your spray thin.             

If you are spraying on a horizontal surface, spray from left to right and not from the center.

On the second layer following the same direction. 

polyurethane case

Meanwhile, if you are finishing a vertical surface, start from top to bottom. This is to avoid the paint from dripping and creating bubbles.   

Continue spraying more coats depending on your preference.


Lastly, after spraying is the drying and cleaning process. Check to see if the surface is already dry and if so, clean it with water.

As mentioned earlier, drying time differs between the water based and oil based paint. Water-based ones usually dry faster.

Take a look at the following video for more tips:

Things to Remember 

  • This material gives out a thick coat so be careful not to overdo layers.
  • Usually, four layers of the coat are enough to cover your surface
  • Be mindful of possible runs and drips when spraying on a vertical surface

Using polyurethanes on your projects is a sure way to make it more beautiful. With its varnish, you can achieve a maple or an amber glow. It also brings out the natural properties of wood.

However, you have to be careful in using one because it is one of the most challenging types of varnish to apply. Before spraying on the actual surface try doing small ones for practice.

In understanding the characteristics of polyurethane and preparing everything from the working space, target surface, to the materials, you will be able to pull off your project successfully.