How to Spray Polyurethane Rather Than Brush – DIY Tips

How To Spray Polyurethane

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Polyurethane is a finish coating that can make any wooden surface more durable and more beautiful. It is a protectant and sealer. It keeps moisture from damaging the wood. It is also a finish coat that brings an immaculate shine and magnifies the beauty of everything from flooring to furniture.

Polyurethane is a
varnish that is specially formulated so that the resin molecules in it will
bond together as it dries. When this bonding happens it causes the varnish to
create a shield of protection around the wood it is applied to.

When you finish an item with polyurethane then the item is protected against:

  • Water and humidity
  • Abrasions and scratches
  • Solvents and other
    spills
  • Day to day life

Before you can begin to spray
polyurethane you need to decide whether to use a water based poly or an oil
based poly.

Water Based Polyurethane VS Oil-Based Polyurethane

Water Based Polyurethane vs Oil-Based Polyurethane

The main considerations between the water or oil-based items will be the durability factor. Oil-based is more durable and will provide a longer lasting finish, but water-based poly is clearer and suitable for all wood types, and colors.

Water-based polyurethane is perfect if:

  • You want the wood you are finishing to retain its natural light coloration.
  • You want each coat of polyurethane to dry quicker. You can usually reapply another layer after waiting for two hours.
  • You want a polyurethane that has a lower number of volatile organic compounds
  • You do not mind applying more coats of the varnish to achieve the finish you desire. Commonly you will need to apply at least three coats of this type of poly to create a surface appearance that you are trying to achieve.
  • You want to be able to clean up using simple water and a mild soap

This type of polyurethane is mixed with acrylic
resins. The acrylic resins cause the liquid to appear cloudy or milky in the
can. It will retain the milky appearance as you apply it to the wood, but when
it dries it will be crystal clear.

This type of polyurethane is not as durable and
protecting as the oil based varieties are.

It is available in gloss, semi-gloss, and a satin
finish.

Oil-based polyurethane should be used if:

  • You want the hardest and most durable finish
  • You like the added richness and warmth it brings to the wooden
    surface
  • You want to complete the polyurethane applications in fewer coats
  • The item you are coating will be subjected to high levels of
    abrasion. Chair-rails, wainscot, and flooring are prime examples of high
    abrasion items.
  • You do not mind waiting a little longer between each application.
    It will take between four and six hours for this type of poly to be dry enough
    that you can apply another coat.
  • You do not mind the higher volatile organic compounds
  • You do not mind using mineral spirits to help you clean up when
    you are finished applying the poly

This is the most durable polyurethane and it provides
the maximum amount of protection to the wood.

You can get this poly in a gloss, satin and a
semi-gloss finish.

You can also get a water-based oil-modified polyurethane.

This type of poly is perfect if:

  • You want the fast drying of the water
    based poly. You can usually apply the next coat after 2 hours.
  • You want the deep amber and rich tones
    that the oil based poly can bring to wood
  • You want to be able to easily clean up
    with only mild soap and water
  • You want the lower amounts of volatile
    organic compounds
  • You want a poly that is compatible with
    all manners and types of wood

With this type of poly you get the durability and
coloration that you like from the oil based products. You also get the fast
drying times and the easy cleanup that you like in the water based products.

This poly is available in gloss, semi-gloss and satin
finishes.

This type of poly will require at least three coats
before it achieves the finish you desire.

Can you spray polyurethane – How to apply

Once you have determined the type of polyurethane that you desire, then you need to decide how you wish to apply this product. You can apply it using a paintbrush or you can apply it using a paint spraying gun.

Using Paint Brush

Properly Apply Polyurethane

If
you apply poly using a paint brush you will quickly discover that you can see
the small delicate lines that the bristles of your brush make. After you apply
each coat of poly you will have to sand it lightly to remove the brush strokes,
dust it completely, and then apply another layer of the product.

You have to use a high-quality brush that has the perfect angle. You also have to develop a feather light touch so that your brush strokes are less noticeable with each poly application.

Many
people have discovered that the paint sprayer will allow you to apply layers of
polyurethane without brush strokes. These sprayers also allow you to apply
lighter coatings of the substance so each layer dries quicker.

How to Spray Polyurethane Paint?

Follow
these easy steps and you are sure to get a beautiful finish from your sprayed
on polyurethane.

  1. Prepare the Item.
  2. You will need to sand
    the item so that it has a smooth and flawless finish.
  3. Then you will fill any
    holes or cracks with a wood filler.
  4. Stain the wood the color
    that you desire
  5. Allow the object to dry
    completely before you begin to apply the polyurethane
  6. Create a dust free environment to work in.

The slightest bit of dust in wet polyurethane can mar the finish.
You can apply the poly in your garage, workshop, or you can even pitch a tent
and apply the poly inside the tent where dust particles cannot be blown onto
your finish.

You will want to read the manufacturer’s instructions and follow
them closely.

  • Choose the right tip
  • Adjust the volume control so you can apply a perfect layer. If you apply too much poly at once you will get runs and drips.
  • The experts say that you should spray the poly on and on each third stroke you should overlap the poly slightly. This helps you to create even coverage.
  • Pour the poly in the sprayer
  • Thin the poly if the manufacturer suggestions recommend that you do so
  • Spray a test sheet of cardboard to determine if the poly is too thick, too thin, or if your technique is going to work properly for you
  • Apply the poly
  • Allow the poly to dry completely
  • Sand the poly and dust all of the particles off of the piece
  • Repeat the poly applications until the item looks and feels exactly like you want it to.
  • Clean your spray paint gun immediately using mineral spirits if you were using an oil-based polyurethane

Polyurethane Tips from the Pros

https://www.youtube.com/watch?v=ZUgQ_lPL_3w

  • Always strip the old finish if any lacquer or wax are present. You
    can test for lacquer or wax by dropping water on the item. If the water creates
    a white spot then there is lacquer or wax present.
  • Stir the can of poly completely. The stirring will combine the
    ingredients so you will get the best color sheen and the most UV protection
    from your poly.
  • Apply poly in thin layers. Thin layers dry more quickly and you
    get fewer drips and wrinkles in thin layers.
  • Always sand between poly coats. You want to use a 220 grit
    sandpaper so it will smooth away the slightest of imperfections.
  • Never be in a hurry when you are applying poly
  • Use a dry micro-fiber cloth and dust the surface after you sand.
    You can also use a cloth dampened with mineral spirits to dust after you sand
    an oil-based poly. You can use a water dampened cloth to dust after you sand a
    water-based poly. The most minute dust particle can cause a blemish in your
    finish. So carefully dust away all residue left by the sanding after each
    application.
  • Never shake your poly
    container. The shaking motion will create air bubbles in the poly. The air
    bubbles will create a pitted surface that feels rough to the touch.
  • Never thin the first
    coat of poly. There is a myth that thinning the first coat will cause the poly
    to adhere more completely. This is a myth and all that the extra thinning does
    is make you have to apply another coat.
  • Never use a tack cloth
    to dust the poly surface. These cloths contain chemicals that react with the
    poly. The reaction stops the poly from adhering as well.
  • NEVER apply wax and then
    try to apply more poly. Wax will interfere with poly.
  • Never smooth over a coat
    of poly using steel wool. Steel wool will leave tiny bits of steel in the poly
    finish and you will not notice them until later when they start to rust and
    corrode. Always use sandpaper between coats.

Safety Precautions to take when Applying Polyurethane

  1. Do not smoke this substance is flammable. Do not store this substance next to gas water heaters or sources of open flames.
  2. Wear a face mask that will help protect you from breathing in the strong fumes. The fumes produced by polyurethane can burn your throat and cause permanent damages.
  3. Wear goggles to protect your eyes while applying polyurethane. Slight splashes of polyurethane into your eyes can have devastating results.
  4. Use in a well-ventilated area. The fumes from the polyurethane can build up and become hazardous if there is no proper ventilation.

Frequently Asked Questions

Is Spray Polyurethane better than brush?

When you use the spray polyurethane you do not have to worry about brush strokes or fibers from the brush being in the finish. You do have to worry about applying the polyurethane so that it is in thin coats that dry quickly and so that you do not see obvious start and stop lines.

How do you apply polyurethane to spray on wood?

You will fill your paint sprayer with your polyurethane and spray a fine mist onto the wooden surface. You must make sure that the wood is lying flat and level when you begin to paint. You must also make sure that you spray in continuous movement so you do not have drips or blobs form.

What type of spray gun is best for polyurethane?

An HVLP gun is the best gun for this procedure. The LVLP gun is basically a gun designed for commercial operations and does not do well with this type of spray paint application process. Be sure to clean your gun thoroughly with mineral spirits after you complete your polyurethane application. Do not let the substance dry on the interior of the gun.

How many coats of water based polyurethane should I use?

It is recommended that you apply at least three coats of this substance. With each subsequent coat the shine will be intensified and the protection will be increased. If you are using the polyurethane on a tabletop or a cabinet top then you might want to apply as many as ten coats.

Final Word

Polyurethane
is the icing on the cake, so to speak. It creates the durable and beautiful
finish that makes your wood projects look their best. The application process
for polyurethane is time consuming, but the time is well spent and the results
will make you glad that you took your time and used this product.

Spraying
on polyurethane allows you to create a coating that has no brush strokes and
fewer imperfections.

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