Man and his daughter painting a wooden fence

Wood Varnish: What You Need to Know

Wood increases the value of your home and adds a sophisticated touch to any space, but it also needs protection from the sun, water, and everyday wear and tear. Learn about the available types of varnish and their different applications, as well as how to use them to keep the wood surfaces in your home looking beautiful for a very long time to come.

Finish Any Wood Surface with a Layer of Protection
If you are using a regular stain (instead of a combined stain and sealer) to highlight the wood’s natural beauty or to change its colour, then make sure you also use a varnish topcoat. It will act as a protective layer and help preserve the wood’s shine and colour.
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Protective Wood Finish Options

There are many varnish choices available on the market today. Every option offers a different level of protection and a unique appearance, so be sure to pick the best one for your needs.

Here are among the most common wood varnish types to consider:

  • Water-based polyurethane dries quickly, which helps to reduce waiting times between coat applications. Because it also dries clear, it is a great choice for showcasing the colour of lighter wood. It may be combined with acrylic, and you can find formulations made for hardwood floors as well. Water-based polyurethane has less of an odour than oil-based varnish and is easily cleaned with some soap and water.
  • Oil-based polyurethane is a hard-finish, oil-based varnish that has a golden finish for a warm appeal. It provides excellent protection for hardwood flooring, though its amber hue is not a preferred choice for lighter woods. It doesn’t need as many coats as a water-based varnish but does take longer to dry. For cleaning, you need to use mineral spirits.
  • Oil-modified polyurethane offers the warm glow of oil-based varnish with the quick drying time of water-based products. It also provides excellent durability for wood floors and requires only soap and water for cleaning.
  • Lacquer is a clear and high-gloss topcoat that dries quickly and is easy to apply. It can be used on most wood and metal surfaces but is generally not used on flooring as it may scratch and tint to an amber hue over time. For cleaning, you will need to use lacquer thinner.
  • Shellac is an alcohol-based topcoat that has a light amber tone, which means it doesn’t usually go well with light woods. This natural finish is suitable for flooring but will not repel scratches as well as polyurethane, so it does require more upkeep. It should not be applied to surfaces used to hold hot plates or mugs as it is not as resistant to heat as other finishes, but it can be used on cured masonry, metal, drywall, and cured plaster. To clean shellac, you can use a water and ammonia mixture or denatured alcohol.

  • Spar urethane is a highly durable and resilient oil-based varnish that protects wood surfaces from damage caused by temperature changes, UV rays, and water. It is commonly used on trim wood and windows that are exposed to sunlight, as well as surfaces that frequently make contact with water, like bars and bathroom cabinets. Mineral spirits are needed for cleaning.
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Pro Tip

Confirm that the products you use are suitable for your prepping, staining, and finishing needs by consulting the manufacturer’s information. For example, you have to use a food-safe product on surfaces that make contact with food.
Selecting the Best Sheen
The sheen of a finish refers to its shine or lustre.
Hardwood floor with a high-gloss varnish

Gloss or high-gloss

Finished that give wood a brilliant shine but makes blemishes easier to spot as well.

Semi-gloss

Finishes that are more muted in their shine.

Satin

Topcoats that have a natural and moderate shine that hides minor imperfections.

Flat\matte

Finishes that have very little shine, which helps obscure even more imperfections.

Other Finishes for Protection and Decoration

There are many more products available for protecting or enhancing the look of wood, such as tung oil, Danish oil, and even finishes made for specific uses like to condition butcher blocks and cutting boards.

Other decorative options include wood effects, washes, and finishes that can make wood look burnt, weathered, ages, or crackled. You can even use certain finishes in the place of stains and topcoats, overtop of stained wood, or to change latex paint into a glaze.

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How to Apply Varnish to a Wood Surface
Whether you want to finish a piece of furniture or a hardwood floor, make sure you follow these easy steps and have the right product for the surface.
Person sanding a piece of wood
How to Prepare a Wood Surface
  1. Before you begin, apply a small bit of stain to some scrap wood or an inconspicuous part of your project. The appearance when dry can be impacted by the room lighting, the stain opacity, and the texture and colour of the wood, so have a look when it is dry for a good idea of what to expect.
  2. Clean the surface of the wood.
    1. TSP is effective and will not damage the wood surface.
    2. Strip away the wax with a wax stripper.
  3. Encourage adhesion by sanding in the direction of the grain using 220-grit sandpaper. Steel wool should not be used.
  4. After sanding, wipe away any dust you created.
Person applying varnish to a wooden box
Steps for Applying Varnish

Here is how to apply varnish depending on whether you have an oil- or water-based product.

Water-Based

  1. Apply with a pad applicator, a good-quality polyester brush, or spray equipment.
  2. Give the first coat 3-4 hours to dry.
  3. Repeat steps above for coats two and three.
  4. Sand the wood in the direction of the grain prior to the final coat application.

Note: Though the product will initially look milky white, it dries clear.

Oil-Based

  1. Apply with a pad applicator, a good-quality bristle brush, or spray equipment.
  2. Wait 8-12 hours, then apply a second coat.
  3. Clean tools using mineral spirits.
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Pro Tip

Follow all safety instructions when applying varnish, and ensure good ventilation while you work.
Common Issues with Varnish Application
Here is a look at some common problems that can occur during wood varnish application. It is important to identify the issue before attempting a fix.
Issue
Possible Cause
Bubbling
  • Application causes:
    • Product too thinly applied
    • Over-brushing
    • Excess ventilation
  • Shaking or stirring of the product
Flaking, cracking, or chipping
  • Too many varnish coats
  • Different type of varnish applied over the other
Tacky film
  • Too thickly applied
  • Applied in humid or cold conditions
  • Incompatible with original coating
Obvious brush strokes
  • Previous coat wasn’t dry before application of the next coat and the brush dragged
Milky or cloudy finish
  • Application in cold temperature
  • Stain was not dry of there was moisture under the finish
  • Product not properly stirred, causing poor stain agent distribution
Hi/Low spots
  • Semi-gloss or satin finish needs to be stirred
  • Different rates of product absorption on the surface
Issue
Possible Cause
Bubbling
  • Application causes:
    • Product too thinly applied
    • Over-brushing
    • Excess ventilation
  • Shaking or stirring of the product
Flaking, cracking, or chipping
  • Too many varnish coats
  • Different type of varnish applied over the other
Tacky film
  • Too thickly applied
  • Applied in humid or cold conditions
  • Incompatible with original coating
Obvious brush strokes
  • Previous coat wasn’t dry before application of the next coat and the brush dragged
Milky or cloudy finish
  • Application in cold temperature
  • Stain was not dry of there was moisture under the finish
  • Product not properly stirred, causing poor stain agent distribution
Hi/Low spots
  • Semi-gloss or satin finish needs to be stirred
  • Different rates of product absorption on the surface
Restoring Wood Quickly and Easily
After a while, even a protective finish will begin to show nicks, scratches, and other minor damage and aesthetic issues. Thankfully, you likely don’t need to refinish the wood if you have the right repair products. Stain markers and pens, tinted wood putty, and wood filler pencils are all available in traditional stain colours for quick and easy repairs.

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