Shou sugi ban, also known as yakisugi, is an ancient Japanese technique for preserving and finishing wood by charring it with fire. The charred wood develops a unique blackened texture that is both visually striking and naturally weather resistant. While the charring process helps protect the wood, an additional finish is usually applied for extra protection and aesthetics.
When choosing a finish for shou sugi ban, there are several factors to consider:
Protection from Weathering
One of the main goals is to protect the wood from moisture, UV rays, and other elements that can cause degradation over time. The finish should form a protective barrier to prevent water penetration and sun damage.
Enhancing the Texture
The charred grain patterns are an integral part of the shou sugi ban look. The ideal finish will enhance the textural qualities rather than obscure them.
Durability
Since shou sugi ban is often used for exterior applications like siding and fencing, the finish needs to stand up to wear and tear over many years.
Ease of Application
Many people char the boards on site, so the finish should be relatively easy to apply without requiring specialized equipment.
Sheen Level
The finish sheen is both an aesthetic choice and a functional consideration. Lower sheen, or matte, finishes tend to retain their look longer than higher gloss options.
With these factors in mind, here are some top finish options for shou sugi ban boards:
Tung Oil
Tung oil is made from the seeds of the tung tree. It penetrates deep into the wood grain to provide moisture resistance. Tung oil also enhances the wood’s natural texture and can be used to create different sheen levels from matte to satin.
Advantages
- Penetrates wood for durability
- Water-resistant
- Enhances natural grain
- Available in different sheens
- Easy application
Disadvantages
- Multiple coats required for best protection
- Not as protective as film-forming finishes
- Requires periodic reapplication
Spar Urethane
Spar urethane is a marine-grade polyurethane finish designed for protection against sun, water and weather exposure. It forms a flexible, UV-resistant film on the wood’s surface.
Advantages
- Excellent UV protection
- Highly water-repellent
- Durable film finish
- Available in various sheens
Disadvantages
- Can present adhesion challenges on charred wood
- Susceptible to yellowing over time
- Higher sheens may obscure texture
Exterior Oil Stain
Exterior wood stains contain oils, pigments, and water-repelling resins. The oil penetrates to protect from moisture while the pigments add color and enrich the grain.
Advantages
- Penetrates and protects wood
- Available in semi-transparent and solid color options
- Enhances texture
- Lower maintenance than film finishes
Disadvantages
- Provides less UV protection than film finishes
- Requires reapplication every 2-4 years
- Color pigments can mask charred grain patterns
Exterior Water-Based Stain
These water-based stains offer protection through water-repelling resins while enhancing the wood’s tone and grain. They are lower in VOCs than oil-based versions.
Advantages
- Penetrates surface with water-repellent resins
- Allows wood texture to show through
- Available in semi-transparent and solid colors
- Lower odor than oil-based
- Easier cleanup with water
Disadvantages
- Less protective than film-building finishes
- Typically requires reapplication after 1-3 years
Exterior Acrylic Stain
Acrylic latex stains contain acrylic binders that form a protective film on the wood’s surface while allowing the texture to show through. They offer good weather resistance.
Advantages
- Form durable, breathable film
- Resist UV damage
- Allow wood texture to show through
- Offer good adhesion on charred wood
- Easy water cleanup
Disadvantages
- Film can crack or peel over time
- Typically requires reapplication after 2-4 years
Factors to Consider When Choosing a Finish
When deciding which finish is best for your shou sugi ban project, keep the following factors in mind:
Use Location
If the wood will be directly exposed to sun and rain, such as on exterior siding, select a more durable finish like spar urethane or exterior acrylic. For items with more protection like pergolas and sheltered furniture, tung oil or penetrating stains may suffice.
Desired Sheen Level
Lower sheen finishes like tung oil and penetrating stains enhance texture best. Spar urethane and acrylics are available in matte, satin, and semi-gloss. Flat finishes hide fewer charred details.
Application Method
Check the preferred application method – brush, spray, etc. – and choose an appropriate finish. Tung oil, for example, is easy to wipe on.
Recoating Needs
Film finishes like urethanes and acrylics last longer before needing reapplication – typically 4-8 years for optimum performance. Penetrating oils and stains will require more frequent recoating every 1-4 years.
Color Change
Bare shou sugi ban grays naturally from UV exposure. Pigmented finishes add color but inhibit this natural weathering. Transparent options like tung oil alter the tone slightly while allowing the wood to age gracefully.
Eco-Friendliness
Most water-based finishes are lower in VOCs than oil-based. Tung oil is derived from a renewable resource. Avoid finishes with toxic ingredients.
Budget
Cheaper penetrating stains may suffice for projects like fencing where durability is less critical. For long-term siding protection, invest in a high-performance urethane or acrylic finish.
Best Finish for Different Shou Sugi Ban Uses
Siding
Exterior spar urethane or acrylic stain
Decking
Tung oil or exterior water-based stain
Fencing
Penetrating oil stain
Pergolas
Tung oil or semi-transparent oil stain
Outdoor Furniture
Tung oil or exterior varnish
Application Tips for Best Results
- Apply finish in temps between 50-90°F
- Do not apply in direct sun or on hot surfaces
- Allow charred wood to dry 72+ hours before finishing
- Lightly sand charred boards to remove soot
- Clean wood with mild detergent before finishing
- Apply thin finish coats according to manufacturer directions
- Allow proper drying time between coats
- Add additional coats until desired sheen is reached
- Wipe away any puddles or drips before drying
- Follow all safety precautions when applying finishes
Maintaining Different Shou Sugi Ban Finishes
Tung Oil
Reapply 1-2 coats annually. Lightly sand and wipe clean before recoating. Refinish as needed to restore appearance.
Penetrating Stains
Plan to re-stain every 2-4 years. Power wash and let dry before reapplying. Stain may need to be stripped if buildup occurs.
Film Finishes
Inspect finish every year for cracks or damage. Clean, lightly sand and recoat as needed to maintain performance. Strip and refinish if finish deteriorates.
Conclusion
Part of the beauty of shou sugi ban is the unique charred texture of the wood. Be sure to select a finish that will protect the wood while enhancing, not obscuring, this distinctive characteristic. For exterior surfaces, go with proven durable finishes like spar urethane or exterior acrylic. Tung oil is a great option for interior applications where you want to showcase the wood grain. Consider the planned use, desired sheen, and reapplication requirements when choosing your finish. With the right finish, you can safely highlight the artistry of shou sugi ban for years to come.