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UNDERSTANDING WOOD FINISHING
UNDERSTANDING WOOD FINISHING
How To Select And Apply The Right Finish
By Bob Flexner
WHY FINISH WOOD, ANYWAY?
Sanitation
Stabilization
Decoration
PREPARING THE WOOD SURFACE
Preparing the Lumber
Sanding and Smoothing
Sponging
Sharpening a Hand Scraper
Sharpening a Cabinet Scraper
Solvents for Removing Cured Glues
Glue Splotches
Dents, Gouges, and Holes
Wood Putties
TOOLS FOR APPLYING FINISHES
Rags
Brushes
Rubbing Pads
Spray Guns and Equipment
Common Spraying Problems
OIL FINISHES
Our Ancestors and Linseed Oil
Applying "Oil" Finishes
Oil Finishes and Penetration
How Oil and Oil/Varnish Finishes Protect
Types of "Oil
Safety and Oil Finishes
Using Wax as a Finish
Bleeding Oil Finishes
Which One Is Which?
How to Tell Which "Oil" You Have
How to Maintain and Repair "Oil" Finishes
Guide to "Oil" Finishes
STAINING WOOD
What Makes a Stain
Understanding Stains
A Guide to Stains
Using Aniline Dyes
Bleaching Wood
Chemical Stains
Ebonizing Wood
Matching Color
A Sampler of Wood Stains
Solvents and Thinners for Dyes and Stains
Compatibility of Stains and Finishes
How Woods React to Stains
Applying Stain
Applying Glaze
Pickling
Common Staining Problems, Their Causes, and Solutions
FILLING THE PORES
Filling the Pores with the Finish
Filling the Pores: Finish versus Paste-Wood Filler
Filling the Pores with Paste-Wood Filler
Using Oil/Varnish Paste-Wood Filler
Using Water-Based Paste-Wood Filler
INTRODUCTION TO FILM FINISHES
What's in a Name?
Sealers and Sanding Sealers
The Way Finishes Cure
Finishing Materials: How They Cure
Stain and Finish Compatibility
Classifying Finishes
Comparing the Three Types
Solvents and Thinners for Various Finishes
Solvents and Thinners
SHELLAC
How Shellac Performs
Shellac as Sealer, Washcoat, and Barrier Coat
Common Problems Applying Shellac
Categories of Shellac
Alcohol
Brushing and Spraying Shellac
Applying Shellac
French Polishing
LACQUER
Nitrocellulose Lacquer
Characteristics of Lacquer
Spraying Lacquer
Applying Lacquer
Lacquer Thinner
The Problem with Lacquer
Fish Eye and Silicone
Common Problems Applying Lacquer
VARNISH
The Mix of Oil and Resin
Characteristics of Varnish
Identifying Varnish Types
Applying Varnish
Brushing Varnish
Common Problems Applying Varnish
Turpentine and Petroleum-Distillate Solvents
WATER-BASED FINISHES
What is Water-Based Finish?
Characteristics of Water-Based Finish
Glycol Ether
Brushing and Spraying Water Base
Applying Water-Based Finish
Common Problems Applying Water Base
CONVERSION FINISHES
Characteristics of Conversion Finishes
Applying Conversion Finishes
CHOOSING A FINISH
Appearance
Protection
Durability
Ease of Application
Safety
Disposing of Your Solvent Waste
Reversibility
Rubbing Qualities
How to Choose
Guide to Finishes
FINISHING THE FINISH
Factors in Rubbing a Finish
Rubbing with Steel Wool
Synthetic Steel Wool
Leveling and Rubbing to a High Gloss
CARING FOR THE FINISH
Causes of Finish Deterioration
Causes and Prevention of Finish Deterioration
Preventing Finish Deterioration
Applying Paste Wax
Furniture Polish in Brief
Applying Liquid Furniture Polish
How to Choose
REPAIRING FINISHES
Repairing Superficial Damage
Applying Padding Lacquer
Repairing Color Damage in the Finish
Compatibility of Colors and Binders
Touching Up Color
Repairing Color Damage in the Wood
Repairing Deep Scratches and Gouges
Using a Burn-In Stick
FINISHING DIFFERENT WOODS
Pine
Pine with Brushing Lacquer
Gel-Stained Pine with Satin Varnish
Toned Pine with Satin Polyurethane
Oak
Oak with Satin Lacquer
Oak with Walnut Oil/Varnish
Pickled Oak with Satin Water Base
Pickled Oak with Satin Lacquer
Oak with Contrasting Pores and Lacquer
A Gallery of Finishes
Walnut
Walnut with Oil/Varnish
Walnut with Orange Shellac and Wax
Mahogany
Mahogany with Wiping Varnish
Stained and Glazed Mahogany with Lacquer
Stained and Filled Mahogany with Rubbed Lacquer
Hard Maple
Maple with Water Base
Maple with Wiping Varnish
Dyed and Glazed Maple with Oil/Varnish
Cherry
Gel-Stained Cherry with Oil/Varnish
Toned Cherry with Rubbed Lacquer
Ash, Elm, and Chestnut
Toned Ash with Satin Lacquer
Soft Maple, Gum, and Poplar
Dyed Poplar with Water Base
Aromatic Red Cedar
Birch
Dyed Birch with French Polish
Oily Woods
Rosewood with Wax
STRIPPERS
Stripping Solvents and Chemicals
Stripper Safety
Using Oxalic Acid
Using Strippers
Choosing Which Stripper to Use
Common Problems Using Strippers
Breaking the Code-An Overview of Strippers
SOURCES OF SUPPLY
INDEX
Why Finish Wood Anyway?
Why do we finish wood? It's an extra step, or steps, that most woodworkers don't find at all enjoyable. It's smelly and messy, and all sorts of things can go wrong. In addition, most woods look pretty good unfinished. Why bother? There are three good reasons for finishing wood: to help keep it clean, to help stabilize it, and to decorate it.
SANITATION
Wood is a porous material. It contains countless holes of various sizes. These holes can accumulate dirt and grime from handling, atmospheric contaminants, and food. Grimy wood is unattractive, and it can be a health hazard, providing a breeding place for bacteria. A finish seals the porous surface, making it less susceptible to soiling and easier to clean.
STABILIZATION
Besides being porous, wood is hygroscopic: It absorbs and releases moisture. Moisture within wood is called moisture content- moisture in the environment is either liquid water or water vapor (humidity). Wood responds to changes in the level of moisture around it. If you put very dry wood in water or in an area of high humidity, the wood will absorb moisture and swell. If you put wood that has a high moisture content in a relatively dry climate, the wood will release moisture and shrink.
These dimensional changes, commonly called wood movement, do not occur consistently throughout a piece of wood. The surface of wood, for instance, responds more readily than the core. Wood swells and shrinks mainly across the grain; that is, in the width and thickness of boards, not appreciably in the length. And wood swells and shrinks more around the annular rings than it does perpendicular to the rings. The result of these different responses is that wood movement generates great stresses in wood and on the joints that hold pieces of wood together. The stresses cause splitting, checking, warping, and weakening of the joints. A finish slows moisture exchange, thus reducing the stresses and stabilizing the wood.
As a general rule, the thicker the coating of finish, the better it limits moisture exchange. This is the reason you should coat all sides of a piece of furniture-top and bottom, inside and outequally. Another important understanding is that moisture exchange in wood does not have to be in the form of liquid water. It can be, and usually is, water vapor. Water-vapor exchange causes much damage to otherwise sheltered wood furniture and woodwork. It just does this more slowly than in wood subjected to liquid-water exchange.
Splits, Checks, and Warps
To better understand how moisture exchange causes splits, checks, and warps, look at Figure 1-1. A solid piece of kiln-dried wood is clamped securely so that it can't expand in width. Then it is saturated with water. The cell walls swell and try to expand but are constrained by the clamps. So the cell walls compress, changing from cylindrical to oval in shape.
If the board is released from the clamps, the cells don't return to their cylindrical shape: They remain flattened. When the water evaporates and the cell walls shrink to their previous thickness, the board shrinks, becoming narrower than it was originally. The amount of shrinkage is as usual, but the starting point is now the clamped width rather than the width the board would have swollen to without the clamps. If the board is reclamped and made wet and dry again, it will shrink further. This phenomenon is called compression shrinkage (also compression set). It explains why nails and screws work loose in wood, and why the wooden handles of hammers and hatchets loosen over time, after becoming repeatedly wet and then dry.
Compression shrinkage also accounts for splits developing in the ends of a board, checks in the middle of a board, and cupping (a type of warp) on the si