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In this article, learn what Danish oil and polyurethane are and how they compare to each other. Find out when to use each one, and which is better.
- What Is Danish Oil?
- What Is Polyurethane?
- Danish Oil vs Polyurethane
- Major Differentiating Factor
- When to Use Danish Oil
- When to Use Polyurethane
- Which Is Better, Danish Oil or Polyurethane?
What Is Danish Oil?
Danish oil is used to darken, protect, and waterproof wood. It dries to a satin finish that is fairly durable, although it can be scuffed. A combination of varnish, drying oil, and various polymers and solvents, Danish oil straddles the line between film-forming and penetrating finishes.
A liquid finish applied to wood dries and/or cures to form a protective barrier. When these barriers form mostly on the surface of the wood, they are called ‘film-forming’. Finishes that form a barrier inside and just on top of the wood are called penetrating finishes.
Danish Oil Makeup
Danish oil contains a drying oil, usually tung or linseed oil. These finishes work by seeping into the pores of the wood and forming a flexible barrier to seal out moisture while allowing the wood to expand and contract somewhat.
It also contains varnish, a film-forming finish composed of resin dissolved with a solvent. When applying a varnish, it dries to the touch within 24 hours, but continue to harden for weeks through a process called curing, reducing the ability of the wood to expand and contract without damage.
It is not possible to know exactly what Danish oil contains as there is no exact formulation. It is even possible to mix Danish oil yourself. The usual ratio is one part varnish mixed with two parts oil, in what is known as a ‘long oil’ formulation.
Applying Danish Oil
The presence of solvents in Danish oil makes it easier to apply and quicker to dry than pure varnish or pure drying oil. Additional solvents can be added to Danish oil to speed the dry time, but these will not affect the longer curing time.
Danish oil will naturally cause wood to appear darker. If additional color is desired, it can be tinted to act as a stain and a sealant in one product. Furniture or wood finished with Danish oil resists liquid penetration. It is frequently used to treat the handles of wood tools, exterior furniture, and the spindles of wooden deck railings.
Danish oil can be brushed or wiped on. It is left to penetrate the wood for a predetermined length of time before being rubbed dry with a lint-free rag. After about eight hours, it can be burnished to a high sheen if desired.
What Is Polyurethane?
Polyurethane is a viscous liquid that, when applied to wood, forms a durable protective layer on top.
There are two types of polyurethane, oil-based, and water. Both contain a combination of resin and solvents. Water polyurethane uses acrylic resins, dries clear, and does not yellow with age or exposure to UV rays. Oil-based polyurethane gradually yellows with exposure to UV light, but is more durable and looks less like plastic.
Polyurethane hardens in two phases. The first is simply drying, and happens as solvents evaporate, taking the moisture out of the finish. The second phase takes longer (about 24 hours for water polyurethane, 30 days for oil) and is called curing.
Polyurethane is a popular and easy to apply finish with good durability. For this reason, it is often applied to areas that see significant traffic, such as wood floors or tabletops. However, skimming, scuffing, marking or wrinkling can occur if the polyurethane is not sufficiently cured.
Not only does polyurethane protect wood from scrapes and scratches, the barrier it forms is waterproof and repels fungus and mildew.
Wipe-on polyurethanes are available. This flexible finish can also be thinned and applied with a compressed-air powered paint sprayer. Spraying polyurethane can make the application process a lot quicker. However, it is usually applied with a brush.
After the first coat has dried, additional coats are added to build the finish. The workpiece is sanded between each layer, which takes care of polyurethane’s frustrating tendency to bubble.
To remove bubbles from the final layer of polyurethane, add a little bit more of whatever solvent you’re using and make the last coat very thin. Brush as slowly as possible and wait about five minutes for the bubbles to pop. ‘Tip-off’ the workpiece by lightly running your brush over the surface to pop any remaining bubbles.
Polyurethane dries to a hard, high-gloss finish. When lower sheen is desirable, deglossers can be added to affect the final outcome of the project.
Danish Oil vs Polyurethane
Danish oil and polyurethane have a lot in common, but there are some important differences, too.
Danish oil and polyurethane resemble each other in appearance, content, toxicity, and mechanism of action.
Danish oil and polyurethane are viscous, transparent liquids that lend a shiny appearance when used to finish wood.
Polyurethane is a type of varnish. Danish oil contains varnish.
Both Danish oil and polyurethane are curing finishes, which means they harden through chemical means. As oxygen molecules are pulled from the air around the finish, they rearrange the molecular structure, binding the particles more tightly together.
Both Danish oil and polyurethane are food safe when the curing process is completed. For water polyurethanes, cure time is about 20 days. For oil-based polyurethane and Danish oil, the timeline is more like 30 days. Always refer to the product guidance for your specific finish before eating off of recently finished wood.
Danish oil and polyurethane are dissimilar in the way they are applied and how they adhere to the wood.
While both finishes cure, only Danish oil penetrates into the wood.
The first layer of polyurethane adheres to the top of the wood, and subsequent coats adhere to that base layer.
Danish oil sinks into the body of the wood, and adheres to the inside of the pores, with a very thin layer remaining on the surface.
Danish oil is usually applied with a brush or a rag, then wiped off after less than 15 minutes.
Polyurethane is usually applied with a brush, then left to dry. Sanding between coats is necessary when applying polyurethane, but not when applying Danish oil.
Major Differentiating Factor
The biggest difference between these two wood finishes is how durable they are.
Polyurethane is the most durable wood finish available, and is tough enough for use on floor, countertops, and kitchen tables.
Danish oil is better for surfaces that see less heavy impact, such as handles and staircase or deck rail spindles.
When to Use Danish Oil
Use Danish oil when you have 30 days to let the workpiece fully cure, in a well-ventilated space, and when looks are more important than scuff-resistance. Danish oil does a good job of protecting wood from moisture, but its barrier is not as tough as polyurethane. Danish oil is also a good choice when you want to darken the tone of wood without changing its color.
Although Danish oil can be used to protect exterior wood, the varnish it contains reduces the wood’s ability to expand and contract, making it better for use in climate controlled environments. Perhaps the best use for Danish oil is to treat the handles of cooking implements and utensils.
When to Use Polyurethane
Use water-based polyurethane when you need a crystal clear or water-white finish that will not yellow over time, or when you need to use the workpiece quickly.
Water polyurethanes have a lower odor and emit fewer VOCs than oil-based polyurethane, so you can finish wood and use it within a few days.
Use oil-based polyurethane for the most durable, scratch, and scuff resistant finish, when a more natural film-forming finish is desirable, or to enhance the color of light woods.
Which Is Better, Danish Oil or Polyurethane?
Danish oil is better than polyurethane for achieving a more natural look.
Polyurethane is better than Danish oil at protecting wood from impact damage and the long term effects from sun and rain.