Wood Finishing

Part of Woodworking

Bare wood is vulnerable to moisture, sunlight, insects, and dirt. A finish is the barrier between the wood and the world. Choosing the right finish determines whether your work lasts a season or a century. Fortunately, effective finishes can be made from materials available in any environment with trees and animals.

Why Finish Wood

Unfinished wood will:

• Absorb moisture — swelling, warping, and eventually rotting
• Dry out and crack — in arid conditions or heated interiors
• Turn grey — UV light breaks down lignin on the surface
• Harbor insects — borers and termites attack unprotected wood
• Stain from use — food, grease, dirt embed permanently in open grain

A finish addresses some or all of these problems. No single finish is perfect for every situation — the right choice depends on the object, its use, and what materials you have.

Surface Preparation

A finish amplifies what is underneath it. If the surface has scratches, tool marks, or torn grain, the finish will highlight them.

Scraping vs Sanding

Method	Advantages	Disadvantages
Card scraper	Leaves glass-smooth surface, no dust, no consumables, fast	Requires skill to sharpen and use
Sandpaper	Easy to learn, conforms to curves	Consumable, creates dust, can round edges
Sanding stones (natural)	Free, reusable, work on flat surfaces	Slow, limited grit range

Scraping is preferred when possible. A card scraper is a flat piece of steel with a tiny hooked burr on the edge. Pushed across the surface, it takes gossamer-thin shavings and leaves a surface ready for finish.

Sanding progression (if sandpaper is available): 80 grit to remove tool marks, 120 to smooth, 180 to refine, 220 for final. Never skip more than one grit level.

Raising the Grain

Water-based finishes and wet environments will raise the grain — tiny fibers stand up, making the surface rough.

1. Wipe the prepared surface with a damp cloth
2. Let it dry completely (1-2 hours)
3. The surface will feel rough — sand or scrape lightly with your finest abrasive
4. The fibers are now broken off. Future wetting will not raise the grain again

Tip

Always raise the grain on items that will contact water — cutting boards, bowls, outdoor furniture. Skip this step for items that will only receive oil finishes in dry environments.

Oil Finishes

Oils penetrate into the wood fibers, hardening inside the wood rather than forming a film on top. They are the simplest, most forgiving finishes.

Linseed Oil

The most widely available traditional finish. Pressed from flax seeds.

• Raw linseed oil — dries very slowly (days to weeks). Multiple thin coats build protection. Excellent penetration
• Boiled linseed oil — has metallic drying agents added. Dries in 24 hours. Better film, less penetration
• Apply with a rag, wipe excess after 15-20 minutes
• 3-5 coats for indoor use, recoat when the previous coat no longer feels tacky
• Darkens the wood and brings out grain figure dramatically

Warning

Rags soaked with linseed oil can spontaneously combust. This is not a myth — it happens. Spread used rags flat on a non-combustible surface to dry, or submerge them in water. Never wad them up and throw them in a bin.

Tung Oil

Pressed from tung tree (Vernicia) nuts. Superior to linseed oil in most respects.

• Dries harder than linseed oil
• More water-resistant
• Does not darken as much over time
• Apply the same way — thin coats, wipe excess, multiple applications
• Less widely available than linseed oil

Walnut Oil

• Food-safe without any treatment
• Dries moderately well (better than raw linseed, worse than tung)
• Excellent for cutting boards, spoons, bowls
• May go rancid in very thick applications — use thin coats

Wax Finishes

Wax creates a soft, pleasant surface with low-level moisture protection. It is not durable enough for heavy-use surfaces on its own but works beautifully over an oil base.

Beeswax

• Melt beeswax and mix with a small amount of oil (linseed or walnut) to create a paste
• Ratio: approximately 3 parts beeswax to 1 part oil by volume
• Apply with a cloth, buff with a clean cloth to a soft sheen
• Reapply every few months for items in regular use
• Food-safe and pleasant smelling

Carnauba Wax

• Harder than beeswax, produces a higher shine
• Comes from the leaves of the carnauba palm (tropical regions)
• Often blended with beeswax for easier application (pure carnauba is very hard)
• Excellent for decorative pieces and turnings

Simple Wax Recipe

1. Shave or grate beeswax into a heat-safe container
2. Add oil (linseed, walnut, or olive) — about 1 part oil to 3 parts wax
3. Warm gently until the wax melts and blends with the oil (do not boil)
4. Stir, pour into a tin or jar, let cool
5. The result is a paste wax ready to apply

Varnish and Shellac

These finishes form a film on the wood surface, providing much stronger protection than oil or wax alone.

Shellac

Made from lac — a resin secreted by the lac insect (Kerria lacca), found in India and Southeast Asia.

• Dissolve shellac flakes in alcohol (ethanol)
• Apply with a brush or pad in thin coats
• Dries in 15-30 minutes — very fast
• Beautiful, warm appearance
• Builds to a high gloss with multiple coats
• Not water-resistant — water leaves white marks. Not suitable for outdoor use or items that get wet
• Easily repaired — new coats dissolve into old ones

Natural Varnish

Traditional varnish is made by cooking a resin (pine rosin, copal, amber) with a drying oil (linseed, tung).

1. Heat the resin until it melts and flows (200-300°C depending on the resin)
2. Slowly add hot drying oil, stirring constantly
3. Cook until the mixture is smooth and pulls into long strings
4. Thin with turpentine (distilled from pine resin) to brushing consistency
5. Apply in thin coats, allowing each to dry fully (24-48 hours)

Warning

Varnish cooking involves very hot, flammable liquids. Work outdoors, away from structures. Have sand or a metal lid available to smother flames. Never use water on a resin fire.

Natural varnish is hard, glossy, and reasonably water-resistant. It was the primary furniture finish for centuries before synthetic alternatives.

Paint and Milk Paint

Milk Paint

A durable, matte paint made from ingredients available on any farm.

Recipe:

1. Mix 1 part hydrated lime (calcium hydroxide) with 1 part skim milk curds (casein)
2. Stir until smooth — this is the binder
3. Add earth pigments for color: iron oxide (red, yellow, brown), charcoal (black), chalk (white), copper compounds (green, blue)
4. Thin with skim milk to brushing consistency

Milk paint adheres well, dries hard, and lasts for decades. It produces a distinctive chalky, matte finish found on antique furniture worldwide.

Lime Wash

For rough surfaces and exteriors (fences, outbuildings, barns):

1. Mix hydrated lime with water to a thin cream consistency
2. Add a small amount of linseed oil or tallow as a binder
3. Apply with a brush in thin coats
4. It carbonates as it dries, forming a durable mineral surface

Exterior Finishes

Outdoor wood needs aggressive protection. Interior finishes will fail within months outdoors.

Pine Tar

• Produced by slowly burning pine wood in a kiln with restricted air
• The dark, sticky liquid that drips out is pine tar
• Thin with turpentine and brush onto exterior wood
• Extremely durable, water-resistant, and pest-resistant
• Traditional finish for boats, fences, log buildings, and wooden shingles
• Dark color — not suitable where appearance matters

Linseed Oil + Turpentine

• Mix 1 part raw linseed oil with 1 part turpentine
• The turpentine helps the oil penetrate deeply
• Apply liberally, let soak, wipe excess
• Reapply annually for best protection
• Good for fence posts, garden furniture, tool handles

Charring (Shou Sugi Ban)

• Char the wood surface with a torch or controlled flame until it is 2-3 mm deep black
• Brush off loose char with a stiff brush
• Apply oil to seal
• The carbon layer resists rot, insects, UV, and fire
• Works best on cedar, cypress, and pine
• Dramatic black appearance

Finish Comparison Table

Finish	Water Resistance	UV Protection	Durability	Food Safe	Ease of Application	Recoatability
Raw linseed oil	Low	Low	Low	No*	Easy	Excellent
Tung oil	Medium	Low	Medium	Yes	Easy	Excellent
Walnut oil	Low	None	Low	Yes	Easy	Excellent
Beeswax	Low	None	Low	Yes	Easy	Excellent
Shellac	Low	Medium	Medium	Yes (when cured)	Moderate	Excellent
Natural varnish	High	Medium	High	No	Difficult	Poor
Milk paint	Medium	Medium	High	Yes (when dry)	Easy	Good
Pine tar	High	High	Very High	No	Easy	Good
Charring	High	High	Very High	No	Moderate	N/A

*Raw linseed oil with metallic driers (boiled linseed) is not food safe. Pure raw linseed oil is debated — use walnut or tung for food contact.

Choosing the Right Finish

Kitchen items (cutting boards, spoons, bowls): Walnut oil, mineral oil, or beeswax. Must be food-safe and easy to reapply.

Indoor furniture: Oil first (linseed or tung), then wax. Varnish or shellac for high-use surfaces like tabletops.

Outdoor furniture: Linseed oil + turpentine, or pine tar. Recoat annually.

Tool handles: Raw linseed oil, rubbed in with use. Never varnish — slick finishes cause blisters.

Musical instruments: Shellac (French polish) for beauty, oil for utility instruments.

Buildings and fences: Pine tar, charring, or lime wash. Maximum durability, minimum maintenance.

Common Mistakes

• Applying too thick — thick coats of oil dry slowly, become sticky, and attract dust. Always wipe off excess
• Not enough coats — one coat of anything provides almost no protection. Most oil finishes need 3-5 coats
• Finishing over a dirty surface — dust, fingerprints, and pencil marks get sealed in permanently
• Using the wrong finish — varnish on a cutting board (toxic), shellac on a garden bench (dissolves in rain), paint on a tool handle (blisters)
• Impatience between coats — let each coat dry fully before applying the next. Rushing creates a sticky, soft finish
• Skipping surface preparation — a finish makes scratches and tear-out more visible, not less

Wood Finishing — At a Glance

Every piece of wood needs a finish to survive moisture, UV, insects, and use. Oil finishes (linseed, tung, walnut) penetrate and protect from within — apply thin, wipe excess, build with multiple coats. Wax adds a pleasant surface over oil. Shellac and varnish form a protective film for higher demands. Pine tar and charring protect exterior wood against the worst conditions. Match the finish to the use: food-safe oils for kitchenware, tough varnish for tabletops, pine tar for outdoor structures. Always prepare the surface first, always apply thin coats, and never wad up oily rags.