DIY Network

Wood Finishing: Surface Prep and Safety Issues From "Wood Works" episode WWK-504

	Great woods are like fine wine. Part of what makes them great is their finish.
	A well-chosen finish not only enriches and protects the wood, it can bring out and accentuate the rich tones, grains and figure inherent in the wood.

Every great piece of furniture deserves a great finish. The finish is the final step in a long series of creative decisions, and should not be taken lightly. Though it's the last thing applied, it's usually the first thing about a beautiful piece of furniture that captures the yet. In this special episode of DIY Wood Works, host David Marks provides some basic information as well as expert advice on a number of wood finishes.

Wood finishing is an art that's been around for 7,000 years. Finishes are used to beautify and protect wood. They penetrate into the wood's pores, and bring out the depth and beauty of the grain patterns. They enhance the natural color of the wood and offer protection against moisture and abrasions.

Exactly how the wood is treated will impact the overall beauty of the piece -- usually quite dramatically. David discusses a range of finishing techniques beginning with surface preparation. Learn about the benefits of tung-oil finish, the use of wax, and elaborate treatments such as fuming or ebonizing wood. In this first segment, David reviews some of the basics of prepping wood prior to applying a finish.

Safety Alert: Always wear protective gloves, and ensure adequate ventilation, when working with wood stains, solvents and other toxic solutions.

Materials may include:

Scrapers -- gooseneck scrapers, cabinet scraper, etc.
Planes -- block planes, etc.
Flexible sanding strip
Carpenter's tape
Sandpaper, various grits
Sanding block
Abrasive pads
"0000" (extra-fine) steel wool
Raking light
Protective gloves
Eye protection
Respirator

advertisement

	Figure A
	Figure B
	Figure C
	Figure D
	Figure E
	Figure F
	Figure G
	Figure H
	Figure I
	Figure J

Surface Preparation

• Surface preparation actually begins as you're building your project. Small things like pre-sanding parts (especially in tight corners), protecting joints with tape during glue-up (figure A) and removal of excess-glue squeeze-out all make the job of finishing easier.

• In the process of assembly, once the glue has dried remove any dried glue-squeeze-out with a hand scraper (figure B) and/or sandpaper.

• To properly prep wood, you'll likely need a variety of hand tools (figure C) such as chisels for cleaning up tight corners, block-planes for leveling joints, cabinet scrapers for flattening surfaces and a variety of hand-scrapers to help bring out the natural beauty of the grain.

• When prepping sculpted curves such as in a cove-cut, use a gooseneck scraper (figure D) to remove saw-marks and high spots. Another useful tool in this type of application is a wood dowel wrapped in sandpaper. Sand the curve with appropriate grit until you reach a fine finish with 220-grit.

• To shape and sand large curves, use a flexible sanding strip (figure E). You can make one of these by simply attaching sandpaper to flexible, thin strips of wood using double-stick tape. The key is to get the entire curved surface blended to a common smoothness.

• When prepping textured surfaces, begin by lightly sanding the wood with 320-grit paper to knock off the sharp edges. Then buff the surface with a synthetic abrasive pad. Finally, burnish the surface using 0000-grade steel wool.

• Another useful tip for finishing a surface is to examine it closely under a raking light (figure F). The angle and intensity of the light will reveal subtle imperfections as well as high and low spots on the surface.

• After prepping and sanding, clean away dust with a vacuum, or (if you have a compressor) blow it away using compressed air.

• At this point, you'll need to consider if you want to continue by raising the grain. This may be especially important if you plan to use a water-based finish or color treatment, or for any piece that might be exposed to moisture. The process basically minimizes future grain swelling. Once you have raised the grain and applied the finish, it will prevent you from sanding through the color.

• To pre-raise the grain by spraying on clean water to soak the entire surface (figure G). After the water sets for a minute or so, wipe away the excess. Allow the wood to dry for a few hours. Sand the surface with 320-grit sandpaper. Remove any dust and burnish the entire surface with steel wool. The steel wool gets down into the pores of the wood and removes minute rough fibers.

Safety and Environmental Issues

Generally speaking, wood finishes are toxic. They can be harmful to your skin, lungs and eyes. If not disposed of properly, they can cause far-reaching damage to the environment. It's vital to handle and dispose of these chemicals in ways that are safe and responsible.

• Always read manufacturer's labels, and read and follow any safety precautions.

• Always ensure adequate ventilation, when working with wood stains, solvents and other toxic solutions.

• Always wear protective gloves when working with caustic or toxic chemicals (figure H). Use vinyl or nitril gloves when working with milder finishes. Use neoprene gloves when working with harsher chemicals.

• Always use safety glasses or goggles when working with toxic chemicals.

• When necessary, use a charcoal respirator (figure I) to help filter out the fumes of the solvents.

• It's advisable to wear an apron to protect your clothes and body.

• Have a well-stocked first-aid kit on hand, as well as a multi-purpose fire extinguisher.

• For environmental safety, never simply pour finishes or solvents on the ground. They can contaminate the water supply. Contact your local waste company to learn the proper ways of disposing of harmful chemicals.

• To deal with used rags, soak them in water before disposing of them (figure J), or store them in tightly sealed metal cans for re-use.

• Note that, in their liquid form, most finishes are toxic. But once the solvents have flashed off or dried, many of them become relatively benign. If you're finishing a woodworking project that will be used by children, use non-toxic coloring and finishing agents.
  

In the segment that follows, David Marks goes over dyes and coloring agents.

Click here to order your tools and materials for this project from Woodcraft!