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Non-Toxic Wood Sealing Guide: Protect Your Woodwork without Harmful Chemicals

By Tobias Roberts Rise Writer
Mar 16, 2023

Wood is a beautiful material, but it's also vulnerable to damage from moisture, pests, and sunlight. Sealing your woodwork is an essential step in protecting it from these threats, but most conventional wood sealers contain harmful chemicals that can be hazardous to your health and the environment. One recent study found that around 80 percent of current wood finishes contain some sort of toxic volatile organic compounds (VOCs). In this guide, we'll introduce you to non-toxic wood sealers and help you make an informed decision about which one to choose.

Table of Contents

  1. What will happen if I leave wood untreated?
  2. What does waterproofing wood do? 
  3. What Are Non-Toxic Wood Sealers?
  4. Why Use Non-Toxic Wood Sealers?
  5. Types of Non-Toxic Wood Sealers
  6. Can you seal fresh-cut wood?
  7. Can all woods be sealed? 
  8. Does sealing wood change the color?
  9. How do you prepare wood for sealing?
  10. How do you apply wood sealer?
  11. How long does wood waterproofing last?
  12. How much does wood sealer cost?
  13. What's the best waterproofing for wood? 

What will happen if I leave wood untreated?

Wood that is not treated or sealed correctly will not be as durable or permanent. When wood is not sealed or protected with a protective coating of polyurethane, urethane, sealants, or some other coating type, it readily absorbs liquid and moistures.

A spilled drink on your wood floor, driving rains that hit your wood siding, and even high humidity levels inside and outside your home can cause the wood to swell, thus leading to warps, cracks, and other imperfections. Furthermore, untreated wood is much more prone to be "infested" by termites, bugs, mildew, mold, and other "pests" that can quickly ruin your wood interior or exterior.

What does waterproofing wood do? 

Waterproofing your wood is the most straightforward way to protect wood against rot, moisture, mold, and mildew. Though there are other natural ways to protect your wood from moisture (check out this Rise article on the Japanese Shou Sugi Ban method), most people rely on varnishes, sealants, and other similar products that are applied to the surface of the dry wood.

Source: guitario via Getty
Source: guitario via Getty

Any wood that is exposed to sunlight, rain, or excessive moisture should be waterproofed as this can help to prevent:

  • Cracks
  • Warping
  • Splitting
  • Discoloration
  • Wear and premature breakdown,
  • Mold, termite, and other pest infiltration.

Waterproofing wood not only protects the wood from moisture (as its name implies) but also plays a vital role in protecting it from long-term exposure to the sun's UV rays.

What Are Non-Toxic Wood Sealers?

Non-toxic wood sealers are natural or planet-friendly alternatives to conventional wood sealers that contain harmful chemicals. They're made from natural materials such as plant oils, beeswax, and water-based resins. Some non-toxic wood sealers may also have low levels of VOCs (volatile organic compounds), which are less harmful than conventional sealers.

Why Use Non-Toxic Wood Sealers?

The main reason to use non-toxic wood sealers is to protect your health and the environment. Traditional wood sealers contain chemicals such as formaldehyde, benzene, and toluene, which can be harmful to your health and the environment. These chemicals can cause respiratory problems, headaches, and even cancer. They can also contribute to air pollution and damage the ozone layer. Non-toxic wood sealers, on the other hand, are safe to use and environmentally friendly.

Look for wood treatments that are safe around gardens
Look for wood treatments that are safe around gardens

Types of Non-Toxic Wood Sealers

There are several types of non-toxic wood sealers available on the market. Each type has advantages and disadvantages, and the choice depends on your preferences and the type of woodwork you're sealing.

Water-Based Sealers

Water-based sealers are made from water-based resins and are the most environmentally friendly option. They're easy to apply, dry quickly, and don't emit harmful fumes. However, they may not be as durable as oil-based sealers and require more frequent reapplication.

Oil-Based Sealers

Oil-based sealers are made from plant oils such as linseed or tung oil. They're durable and offer excellent protection against moisture and UV rays. However, they may emit harmful fumes during application and require longer drying times.

Wax-Based Sealers

Wax-based sealers are made from natural waxes such as beeswax or carnauba wax. They offer good protection against moisture and are easy to apply. However, they may require more frequent reapplication and may not be as durable as other sealers.

Shellac-Based Sealers

Shellac-based sealers are made from natural shellac - a resin from the female lac bug. It's quick drying and provides a hard finish. It's easy to repair because old layers of shellac can be removed with alcohol. Shellac is prone to damage from hot pans and water, so it's not a top choice for kitchens and bathrooms.

Can you seal fresh-cut wood?

Before treating wood with any sealant or waterproofing agent, it is important to ensure it is completely dried out. Wet wood, also called green wood, will continue to shrink as it loses water, which can negatively affect the sealant.

Fortunately, most of the wood products you purchase from lumber yards, home improvement stores, and similar commercial venues will have already been dried. If you are harvesting the wood on your property, allow the wood to dry properly before sanding and sealing the wood.

Can all woods be sealed? 

Some highly dense exotic woods are challenging to seal since the sealant has a harder time penetrating the wood's pores. In some cases, you might not need to seal exotic woods, especially for interiors where they will not be exposed to regular moisture or excessive traffic.

If looking to seal exotic wood, it's best to avoid using oil-based sealants, including polyurethane, the most common type of wood sealant. Oil-based sealants don't work well with many kinds of exotic wood because the chemical reaction that oil-based sealants cause in standard wood types does not happen with exotic wood types. Furthermore, clear sealants are usually preferred with exotic woods as they allow the natural textures, grains, and hues of the exotic wood to shine through.

Instead of using oil-based polyurethane sealants, consider using a few coats of de-waxed shellacs before putting on a top coat.

Does sealing wood change the color?

Homeowners can choose from several different wood sealant products, including stains or pigmentation. However, if you prefer the natural look of the wood, you can opt for clear sealant products.

Wood finishes of any type, including polyurethane, shellac, lacquer, wax, and varnish, will always alter the wood's appearance by accentuating the grain and texture of the wood. In general, sealants will also darken and deepen the natural color of the wood. If you want to avoid that glossy, shiny, amber-golden look, opting for oil-based polyurethane sealants or finishes is probably not a good idea.

Choose the right wood treatment for your unique project
Choose the right wood treatment for your unique project. Source: tang90246 via Getty

How do you prepare wood for sealing?

To prepare wood for sealing, here is a quick checklist to help you with the process:

  1. Check the moisture content of the wood: Trying to seal wet wood is a recipe for failure, as the sealant will not properly adhere to the wood. Exterior wood surfaces should have at most 15-20 percent moisture while interior wood should be between12-15 percent. You can purchase a moisture meter if you are unsure if your wood is too wet.
  2. Seal all knots: If you are working with bare wood, prime all the knots with a shellac-based primer.
  3. Fill in the cracks: Use a high-grade interior or exterior grade wood filler to seal any visible cracks or holes in the wood.
  4. Sand the wood: Lastly, use 150g – 220g sandpaper and sand in the direction of the wood grain. Going against the grain could lead to scratches that will absorb your stain or sealant unevenly.
Sanding a wood bench before cleaning and staining
Sanding a wood bench before cleaning and staining

How do you apply wood sealer?

Once you have prepared your wood surface by sanding and cleaning, you will be ready to apply the sealant. Use high-quality brushes or rollers. If you are working with water-based polyurethane, do not stir too harshly, as this could lead to bubbles. Also, only put more sealant on the brush if necessary, and do firm, long strokes following the wood grain. Wait to apply a second coating or paint over the same area until it completely dries.

Applying wood stain to a bench
Applying wood stain to a bench

How long does wood waterproofing last?

An exterior wood surface that sees heavy foot traffic and is directly exposed to sun and moisture should be resealed every one to three years. An interior surface that doesn't receive much foot traffic should only need to be resealed every ten to fifteen years.

How much does wood sealer cost?

The exact cost of wood sealant will depend on the quality of the product you purchase. Though it is possible to find relatively cheap wood sealants, these products are generally less durable and may off-gas dangerous VOCs into your home. For comparison's sake, a 5-gallon bucket of AFM Naturals Oil Wax Finish costs $570 here at Rise, enough to cover 1750 square feet.

Vermont Natural Coatings PolyWhey Exterior Wood Stain
Vermont Natural Coatings PolyWhey Exterior Wood Stain

What's the best waterproofing for wood? 

Several non-toxic wood sealant products are on the market today. Some of the top brands include Vermont Natural Coatings, AFM Safecoat, nd Zinsser.

  • Vermont Natural Coatings: This innovative company uses a patented formula that harnesses the power of whey protein, a byproduct of cheese making, and uses these proteins to replace the toxic ingredients traditionally found in wood finish. Their Penetrating Water Proofer is a natural wood preservative product that seals the wood from the inside, extending the life of the wood by controlling moisture, thus reducing mold and decay. The waterproofer uses Juniper as a powerful natural wood preservative. The result is a long-lasting, zero-VOC waterproofer that is safe for people, pets, and the environment.
  • AFM Safecoat: This company uses natural mineral pigments instead of dyes and no formaldehyde or other toxic ingredients. The strong, durable finish has no harsh solvents, fumes, or odors. AFM Naturals™ Oil Wax Finish is a plant-based hardener and sealer for wood, bamboo, and cork flooring. It can also be used on other wood surfaces, including children's toys and furniture.  
  • Zinsser's Shellac Sealcoat: Zinsser offers a great shellac-based wood sealant. Shellac is a substance from insects but acts as a safe wood sealant. Shellac is not a great option for the kitchen as it does not stand up to alcohol.

No matter what type of wood sealant option, finding a natural sealant is the best way to drastically reduce the dangerous VOC emissions off-gassing into your home.

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2023-03-16T19:22:52+0000
Tobias Roberts

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.

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