The finish is the first thing most people notice about a piece of woodwork. A good finish can lift an ordinary piece, and a poor one can spoil weeks of careful work in an afternoon. Many beginners rush finishing, and many experienced woodworkers find it the least enjoyable stage, which is exactly why it repays planning and the right supplies.
This post covers sanding before finishing and choosing sanders, the main types of finish, the supplies a small shop needs, brushing, thinning and sanding between coats, pre-finishing parts before assembly, and working safely with finishes. For a business, a consistent, durable finish is part of what buyers pay for.
Sanding Before Finishing
Almost every piece needs sanding before finishing, to remove machine marks, scratches and glue and leave an even surface that takes finish well. Fine Woodworking’s finishing expert Jeff Jewitt starts no coarser than 100 grit, then works through 120, 150 and 180 to 220 grit. Do not skip grits; each one removes the scratches of the one before. Finish by hand-sanding with the grain, using the last grit you used on the machine, to remove any swirl marks.
- Scrape off dried glue with a card scraper before sanding. Glue left on the surface clogs paper and blocks stain.
- Sand parts before assembly where you can. Corners and inside edges are much harder to reach once a piece is put together.
- Very fine sanding before stain can make the wood absorb less stain. Test your sanding and stain on scrap of the same wood.
- Vacuum and wipe off all dust before applying finish.
Random Orbital Sander
A random orbital sander is the main sander in most shops. Its pad spins and moves in small, random orbits at the same time, which leaves far fewer swirl marks than a sander that only spins or vibrates.
- Size: 5-inch sanders are the most common; Jewitt prefers a 6-inch pad on large surfaces for its larger area. Choose one that is comfortable in one hand.
- Hook-and-loop pads make changing discs quick and hold better than adhesive discs, which lose grip after repeated changes.
- Dust port: choose one that connects to a shop vacuum; small bags fill fast.
- Variable speed helps with fine work and finishing between coats.
Keep the sander moving and flat, and let its weight do the work. Pressing hard slows the pad and leaves swirls. If you need to press, the disc is worn or too fine. Round pads do not reach into corners, so finish those by hand or with a detail sander.
Belt Sander
A belt sander runs a continuous abrasive belt over two rollers. It is the most aggressive sander, used for flattening panels, removing heavy marks and shaping. It can take off a lot of wood quickly, and can just as quickly gouge a surface.
- Practise on scrap of the same wood first.
- Keep the sander moving and flat. The front tends to lift; keep even pressure.
- Do not press down; the sander’s weight is enough.
- Sand with the grain for the final passes.
- Jewitt favors a heavy 4 by 24-inch sander for flattening, and making several passes across the panel diagonal to the grain, then diagonal the other way until the scratch pattern is even.
- Follow belt sanding with a random orbital sander and hand-sanding.
Belt widths run from about 2 1/2 to 4 inches. Wider belts are easier to keep flat and remove wood faster. Look for a dust port that connects to a vacuum. Variable speed matters mainly if you sand materials other than wood.
For sanders in a starter tool kit, see woodworking tools for beginners.
Types of Finish
- Oil finishes (tung oil, linseed oil, Danish oil and oil-varnish blends): easy to apply by wiping, soak into the wood and give a natural look. They offer modest protection and need reapplying over time.
- Wax: a soft sheen over bare wood or another finish. Little protection on its own.
- Shellac: dries fast, gives a warm color and works as a sealer under other finishes. Damaged by alcohol and heat.
- Lacquer: dries very fast and is usually sprayed. Common in professional shops.
- Varnish and polyurethane: durable film finishes that resist water, heat and wear. Oil-based versions amber slightly; water-based versions stay clear.
- Water-based finishes: lower odour, easy water clean-up and fast drying. They have improved greatly and are now widely used, including in home shops.
For cutting boards and other food-contact items, see the finish guidance in top woodcrafts to sell.
Essential Finishing Supplies
1. A Clean Finishing Area
Dust in the air settles on wet finish, and every speck has to be sanded out later. The cleaner the air when you apply a coat, the better the result.
- Use a separate small room or a corner of the shop for finishing if you can.
- If you cannot, set a day aside for finishing, when no dust-making tools run, and run an air filter.
- Collect dust at the source when you do cut and sand. See woodshop dust collection.
A few dust nibs can be sanded out between coats, so a perfectly dust-free room is not essential. Water-based finishes dry faster than oil-based ones, so they have less time to collect dust.
2. Ventilation
Finishes give off vapors that you should not breathe for long. Ventilation comes first: an exhaust fan set fairly high in a wall pulls fumes out without stirring dust from the floor onto wet surfaces. Pair it with an opening on the other side for fresh air.
3. Respirator, Glasses and Gloves
- Respirator: use a half-face or full-face respirator with organic vapor cartridges for solvent-based finishes, and add particle filters if you spray. Cloth and paper masks do not stop fumes. People with beards cannot get a seal with a tight-fitting respirator; a powered respirator with a hood or helmet is the alternative. See woodshop dust collection for respirator ratings.
- Safety glasses: drops of finish can splash into your eyes from a brush or spray. Wear glasses for all finishing work.
- Gloves: thin nitrile or vinyl gloves protect your hands from stains and solvents without losing your sense of touch. Check the finish label for the right glove material.
4. Fine Abrasives and Non-Woven Pads
Sanding between coats removes dust nibs and gives the next coat a surface to grip. Use fine paper, such as 320 or 400 grit, between coats, and finer wet-and-dry paper, up to around 2,000 grit, for rubbing out a final coat to an even sheen.
Sanding a coat that has not fully dried clogs the paper and tears the finish. Let each coat dry fully; check the label, as some finishes need a day or more.
Non-woven abrasive pads, such as Scotch-Brite hand pads, are a useful alternative. They do not clog as quickly, follow curves, can be used in any direction, and can be tapped clean and reused. 3M grades its maroon pads as very fine, gray as ultra fine and white as the finest, for light rubbing and buffing. They feel gentler than they are, so try them on a finished scrap first.
5. Brushes
- Natural bristle brushes suit oil-based finishes, shellac and varnish.
- Synthetic brushes suit water-based finishes. Natural bristles soak up water and go limp.
- Artist’s brushes in small sizes reach corners, crevices and missed spots, and are useful for touch-ups.
- Foam brushes and lint-free cloths work well for wiping finishes and stains.
6. Solvents
Solvents clean brushes and spills, and thin finishes so they flow out and soak into the wood. Thinning also lets you build several thin coats, which give a stronger, smoother finish than one thick coat, especially on open-grained woods such as oak. Use the solvent the label specifies:
- Mineral spirits for oil-based varnish and polyurethane.
- Denatured alcohol for shellac, including shellac you mix yourself from flakes.
- Lacquer thinner for lacquer.
- Water for water-based finishes.
If you mix your own finish, such as shellac from flakes, write down the ratios so you can repeat the result.
7. Jars, Strainers and Filters
Pour a small amount of finish into a clean jar to work from, and keep the main can sealed, so it does not thicken or collect dust. Strain finish through a paint strainer or filter before use to remove lumps and particles, which saves hours of sanding out defects.
Applying Finish
- Test the full finishing sequence on scrap of the same wood.
- Dip the brush only about a third to halfway up the bristles. It holds enough finish, cleans more easily, and traps fewer air bubbles.
- Brush in long strokes in one direction, with the grain. Working back and forth whips air into the finish and leaves bubbles and streaks.
- Apply several thin coats rather than one thick coat. Sand lightly between coats once each is fully dry.
- Finish all sides of a panel or top, so moisture moves in and out evenly and the wood does not cup.
Caring for Brushes
A good brush can last for years with proper cleaning. Clean it straight after use in the solvent for the finish, then wash out the solvent gently with warm soapy water, working the bristles apart with your fingers. Let it dry flat and store it in a zip-top bag or its original cover to keep its shape.
Pre-Finishing: Finishing Parts Before Assembly
Corners, slats, spindles and inside surfaces are hard to sand and finish once a piece is assembled. Pre-finishing means sanding and finishing the parts before you put them together. For pieces such as chairs, cabinets with many inside corners and frame-and-panel doors, it is easier, faster and gives a better result, because every surface can be laid flat, turned and inspected.
How to Pre-Finish
- Sand all parts to the final grit.
- Mask or protect glue surfaces, such as tenons, mortises and the edges of joints, with tape, so glue will bond to bare wood.
- Find a surface on each part that will be hidden once assembled, such as the top of a chair leg that fits into the seat. Drive a small screw hook into it to hold the part while you finish all its visible faces.
- Apply finish, then hang the part by the hook to dry, so no wet surface touches anything.
- Hang parts on a line or rack. Heavy parts make a wire or clothesline sag, so parts slide together; tie slipknots in a nylon line, or wrap tape around a wire, to keep each part in place.
- Assemble once the finish is dry, and touch up any marks.
Raised panels in doors are a common case for pre-finishing: finished before assembly, they do not show a bare line when the panel shrinks in winter.
Finishing Safely
- Read the label. Labels and safety data sheets list the hazards, ventilation needs and protective equipment. If the label says to work in a well-ventilated area, do.
- Oily rags. Rags used with oil finishes can heat up and catch fire on their own as they dry. Fine Woodworking’s Jeff Jewitt says more finishing fires are probably caused by this than anything else. Soak used rags in water, then hang them or spread them flat outdoors to dry before throwing them away. Never leave them in a pile or a closed bin.
- Flammable finishes. Keep solvent finishes away from heaters, pilot lights and sparks. Keep an ABC fire extinguisher near the finishing area.
- Waste. Do not pour finishes or solvents down the drain. Use your local hazardous waste program; dried finish residue can go in regular trash.
- Sanding dust. Wear a respirator for sanding and collect dust at the sander.
See woodworking safety rules for more.
Finishing Products You Sell
- Standardise your finishes. Use the same tested finishing sequence for each product, so pieces match from batch to batch and photos match what buyers receive.
- Choose finishes for the use. Hard-wearing film finishes for tables and desks, food-safe finishes for kitchenware, outdoor finishes for garden pieces.
- Allow curing time. Many finishes take days or weeks to fully cure. Build this into your delivery times and do not pack pieces too soon.
- Include care instructions. Tell buyers how to clean and maintain the finish, such as re-oiling a cutting board.
- Price the finishing time. Sanding and finishing can take as long as building. Count it when you set prices.
For common finishing problems such as blotchy stain and glue spots, see woodworking mistakes and how to fix them.
Practical Tips
- Sand through the grits without skipping, and finish by hand.
- Test the full finishing sequence on scrap.
- Apply thin coats and let each one dry fully.
- Keep finishing separate from dust-making work.
- Handle oily rags safely every time.
Sources
- Jewitt, 2020, Power-Tool Flattening, Fine Woodworking
- Jewitt, 2020, Fire and Disposal Safety, Fine Woodworking
- 3M, n.d., Scotch-Brite Hand Pad Product Selection Guide, 3M
