How to Seal Wood: A Beginner-Friendly Guide

Ready to finish your next DIY project? This beginner-friendly guide will teach you about different types of wood sealers and how to apply them. 

Getting to the end of a DIY project is exciting but choosing the right finish to protect your work can be confusing.

There are so many options, from oils to varnishes, water-based and oil-based, each with its benefits and drawbacks. I remember spending hours researching and trying to figure out which finish would best suit my projects, often feeling more confused than when I started.

This beginner-friendly guide to wood sealing is designed to share and help you understand the different types of wood finishes, their uses, and how to choose the best one for your project.

My goal is to make this process easier and less stressful for you, so you can enjoy the satisfaction of completing your woodworking project knowing it will last for a long time to come.

What Is Wood Sealer? 

Wood sealers, also known as sealants, are protective coatings that enhance the durability and longevity of wood surfaces. Sealants can be water-based, oil-based, or solvent-based and come in various forms, including clear coatings, varnishes, and lacquers. Each has its own distinct features, making it ideal for different projects. 

The choice of wood sealant depends on your project’s specific needs, the desired appearance, and the level of protection required. Understanding the properties and applications of each type of wood sealant can help you make the best decision for your wood projects to make sure they are both beautiful and long-lasting. We will dive into all the information and differences below.

What Does Wood Sealer Do?

Wood is a porous material that absorbs liquids. When a wood sealer is applied, it penetrates the wood’s surface and fills the pores. This penetration helps to reinforce the wood from the inside, providing internal protection. This is crucial for protecting the wood from rot, swelling, and warping.

Many wood sealers also form a protective film on the wood’s surface. This film acts as a shield against physical damage, UV rays, and spills. The thickness and hardness of this surface film can vary depending on the type of sealer used.

What To Use To Seal Wood 

Choosing the right sealant for wood depends on various factors including the project’s purpose, desired finish, and wood type.

Here is a quick breakdown of the most common sealants:

1. Polyacrylic

Polyacrylic is a water-based blend of acrylic resin and one of the most commonly used protective top coats.

• It dries clear without adding any yellow tint and does not yellow over time.
• It has a low odor and dries quickly.
• Since it is water-based, clean-up is extremely easy with mild soap and water. I also like using polyacrylic in my paint sprayer because the clean-up is no different from that of water-based paint.

It is great for indoor and low-traffic surfaces because it can dent easily.

2. Polyurethane

Polyurethane is a synthetic resin that provides a hard, durable, and protective coating. It is available in both oil-based and water-based formulations.

• Polyurethane is resistant to scratches, heat, chemicals, and wear, making it perfect for high-traffic areas and surfaces exposed to frequent use.
• Oil-based polyurethane adds a warm, amber glow to the wood which can enhance the beauty of the wood grain if that is the intention.
• Water-based polyurethane emits fewer fumes and dries quickly. It is also easier to clean up with soap and water.

Polyurethane is commonly used on high-traffic areas like floors, furniture, cabinets, and trim.

3. Lacquer

Lacquer provides a high-gloss, durable finish that enhances the wood’s appearance. It is commonly used on furniture and cabinetry. It dries quickly and can be applied in multiple thin coats for a smooth finish.

Unfortunately, you have to apply it carefully as it can be prone to cracking and requires proper ventilation during application due to strong fumes.

4. Shellac

Shellac is a natural resin dissolved in alcohol and provides a rich finish that enhances the grain of the wood. It can be tinted to achieve different shades. It is easy to apply but it is not as durable as synthetic sealants. It is good for indoor furniture and decorative pieces.

5. Varnish

Varnish is a combination of resins, oils, and solvents that provide a hard, protective finish. It is actually a family of top coats that includes spar varnish (for outdoor use), alkyd varnish, and polyurethane varnish.

It is durable and water-resistant, great for both indoor and outdoor projects. It dries slowly and can yellow over time.

6. Danish Oil

Danish oil is a blend of oil and varnish, providing a protective finish that penetrates the wood. It is pretty easy to apply—you just rub it on. It gives the pieces a natural, hand-rubbed appearance. It is great for furniture. I use it every time I use Walnut in my projects, like the tall bar cabinet.

It provides moderate protection but needs to be refinished after a period of time.

7. Tung Oil

Tung oil is a natural oil extracted from the nuts of the tung tree, known for its water-resistant properties. It penetrates deeply into the wood, providing a durable, flexible finish. It enhances the wood’s natural grain and offers a warm, matte appearance.

It provides good protection against water and alcohol but requires multiple coats and regular maintenance.

8. Linseed Oil

Linseed oil is derived from flax seeds and is one of the oldest wood finishes. It is available as Boiled linseed oil (dries faster) and raw linseed oil (dries slowly). Just like Tung oil, it requires regular maintenance and can yellow over time.

Wax as Wood Sealant

Wax is a traditional method of sealing wood and gives it a natural, beautiful finish. It is typically made from beeswax or carnauba wax, but petroleum-based synthetic waxes are also available. To apply wax, it is rubbed onto the surface and then buffed for a smooth finish.

It does offer decent protection against water and wear but needs to be reapplied to maintain its appearance and durability.

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How to Apply Wood Sealer

Before starting, make sure you are working in a well-ventilated space—either outside or in a large room with open windows—as most sealants contain volatile organic compounds (VOCs) that are toxic when inhaled in large amounts.

Another important thing to keep in mind is that the temperature and humidity of the workspace makes a huge difference. If it is too hot, the sealer will dry faster than it is able to level and leave streaks. If it is too humid, the top coat might get a milky white appearance.

Step 1: Prepare the Wood Surface

Before sealing, it is important that the wood is prepared properly.

• You want to make sure that the surface is sanded with 220 Grit sandpaper to remove any roughness before applying the top coat. If you have a stain or paint on the surface, be careful to sand very lightly so you don’t damage it.

Step 2: Clean the Surface

This is an extremely important step. The top coat permanently seals anything on the surface.

• I like to use a wet rag to clean up any residues and once that is dry, I use a tack cloth to wipe off any dust.

Step 3: Prepare the Top Coat

• Stir the sealant well using a stir stick. Slow movements will help prevent air bubbles from forming. Do not shake the can as this will cause a lot of air bubbles and they won’t be able to escape while curing.

Step 4: Apply the Top Coat

• Using a clean good quality synthetic brush, or foam brush apply the sealer according to the manufacturer’s instructions, layering thin coats and following the direction of the wood grain to prevent streaking.

Do not over-brush, i.e., go over the same area multiple times with the brush as this will cause a lot of streaks. Most top coats are self-leveling and will even out when given the right amount of time to cure.

Note: The sealer may look a little milky when applied. As it dries, it will turn clear.

• If you are using a sprayer, make sure you spray in even coats at a uniform speed across the project and don’t change directions in the middle of the piece, as this can cause drips or excess top coat buildup.

Step 5: Sand/Repeat

How many coats of sealant you need to apply will depend on the type of sealant you are using. Be sure to check the manufacturer’s directions. I recommend at least 3 coats on high-traffic areas like table tops and 2 coats on other parts for proper protection. 

• Sand between coats with a fine grit sandpaper like 400 Grits. Wipe off all the sanding dust with a tack cloth.
• Repeat for the next top coat.

Pro Tip: Use a brown paper bag for the very final sanding to get the smooth buttery finish!

How to Seal Wood After Staining or Painting

The best way to seal wood that has been painted is often with a polycrylic sealant. Its water base makes it compatible with painted surfaces and offers a clear, protective layer without affecting the paint’s color. Oil-based polyurethane can also be used, but it may cause the paint to yellow slightly over time.

Stained wood offers more flexibility in terms of sealants. Polyurethane, either water-based or solvent-based, is a great option that provides protection and enhances the stain color. Varnish can also be used, giving the wood a warm, amber tint. A wax sealant can also be applied for a natural look, but keep in mind its limitations regarding water and scratch resistance.

Sealing Wood for Weather Resistance

Unfortunately, when it comes to wood projects meant for the outdoors, most standard sealants will not work. Here is where spar urethane enters the picture.

Spar urethane is a specialized sealant formulated to withstand the elements. It provides a watertight barrier with UV protectants and mildewcide to prevent fading, cracking, and mold growth. Spar urethane also comes in clear and tinted finishes, which allows you to customize your project.

What Is the Difference Between Spar Urethane and Polyurethane?

The main difference between spar urethane and polyurethane is that polyurethane is primarily designed for indoor use, prioritizing aspects like scratch and wear resistance. While polyurethane has some water resistance, it is still not ideal for prolonged exposure in an outdoor environment. 

On the other hand, spar urethane is made specifically for outdoor use with superior weatherproofing abilities. It creates a flexible yet durable barrier that shields the wood from moisture, UV rays, and extreme temperatures.

Choosing the Right Spar Urethane:

Spar urethanes come in two main categories: oil-based and water-based. Here is a breakdown to help you decide:

Type of Spar Urethane	Advantages	Disadvantages
Oil-based	– Lifespan of up to 5 years – Higher water resistance – More traditional look	– Strong odor – Longer drying time – Prone to yellowing over time – Requires cleanup with solvents
Water-based	– Low odor – Faster drying time – Easy cleanup	– Requires reapplication every 1-2 years – Lower water resistance

FAQs

Does stain seal wood? 

Wood stains can have some protective properties, but their degree of protection is limited compared to sealants, especially when it comes to preventing water and sun damage. 

Do you need to seal stained wood? 

I recommend sealing stained wood for most projects, as sealants offer far greater protection than stains and will make your projects much more durable. I would especially recommend sealing stained wood if it will be used outdoors or exposed to frequent wear and tear. However, you could probably get away with using only a stain for decorative, indoor projects that will not be subject to frequent use. 

So, there you have it! Sealing wood does not have to be scary – now you have all the information you need to choose the best sealant for your project so it keeps looking gorgeous for years to come!