Читать книгу Finishing Techniques for Wood Crafters - Lora S. Irish - Страница 11

Once a project is complete, you may want to give all raw wood, burned wood, and painted surfaces a final sealer or finishing coat to protect them from the environment and from UV rays. As we work through the techniques and projects in this book, we will see several options for final finishes you can use. They can include boiled linseed oil (BLO) mixed with turpentine, Tung oil or Danish oil, spray or brush-on polyurethane sealer, brush-on acrylic sealer, a rub and buff wax finish, and hand buffing with a soft cloth. Here is a brief summary of each finish, followed by more details about each one.

• Acrylic Sealer: A soft polymer sealer, acrylic sealer is available in multiple sheens from dull matte to high gloss, dries quickly, dries crystal clear, and does not change or affect the color of the wood or paint. Use on decorative, highly detailed painted projects.

• Paste Wax: This is easy to apply, leaves a non-slick finish, seals the wood surface without leaving a plastic or oil feel, and can be reapplied over the lifetime of the piece. Use on any project that will be handled, held, or gripped.

• Hand Buffing: Some coloring agents like watercolors, pastels, and colored pencils do need a finishing layer or sealer applied to the project to protect the colors from damage or moving. Oil paints, which penetrate into the wood fibers, and acrylic paints, which are polymer-based, do not require a protective sealing layer, as they create their own semi-hard, durable, dirt-resistant finish. To strengthen that self-sealing surface, however, you can buff the painted surface with a dry, clean cloth after the paint is thoroughly dried. Buffing acts like a polishing process, leaving the painted surface with a soft sheen and smooth feel. If you want to avoid excess use of oils or chemicals, or just want a vintage look, try hand buffing.

• Boiled Linseed Oil: This works as a pre-treatment that can be covered with other sealers, infuses the wood deeply with the oil, prevents the project from excessive drying, can be reapplied over the lifetime of the piece, and does not hide or cover the wood grain of the work. Use whenever you may want to make carving or painting changes to the project after a finish is applied.

• Danish Oil: This leaves a soft to glossy sheen with a hard finish, is excellent for decorative items, and is easy to reapply over the lifetime of a piece. Use on any decorative project when you do not want the finish to overpower the painting work.

• Tung Oil: The hardest of the oil finishes, tung oil is used primarily for furniture, leaves a soft sheen, and emphasizes the color changes in the wood grain. Use on a project that will receive hard use or where you want the wood grain to be an emphasized feature.

• Polyurethane Sealer: The hardest of the polymer sealers, polyurethane sealer is used commonly for furniture and floor finishes, is easy to apply and quick to dry, and can be used on indoor and outdoor projects. Use on any project that will be subject to hard, constant use.

Boiled Linseed Oil

Boiled linseed oil penetrates deeply into the wood surface. It leaves a very soft sheen to the surface of the wood and often darkens the overall tonal value of a project. To facilitate the penetrating properties of boiled linseed oil, you can mix it one to one with turpentine. You want the oil to be thinned to a thickness that can be brushed, but not as thin as water. Apply one coat at a time, brushing each coat well to avoid allowing any puddles to form. Let the coat set for about ten minutes, then wipe the project well with a dry, clean, cotton cloth. After two to three coats have been applied, allow the project to dry overnight.

Advantages: This oil finish does not leave a visually hard coating on top of the project, and instead accents the wood grain and woodworking steps. It adds long-term protection to the wood by preventing it from excessive drying while repelling excess water moisture. You can re-carve or even repaint areas of a project once the first coats of BLO dry thoroughly.

Possible Problems: Rags, cloths, papers, and brushes that have been soaked in BLO and/or turpentine can be susceptible to spontaneous combustion. When using any oil-based finish, stain, or solvent, remove all oily rags, cloths, and papers from your work area immediately after use and submerge in a solution of water and dishwashing soap until you can properly dispose of them according to local refuse laws. Clean the brushes using a solution of dishwashing detergent and water.

1. Start applying a boiled linseed oil/turpentine mixture to the piece.

2. Apply oil all over the piece, making sure to get around the sides and edges.

3. After allowing the oil coating to sit for about ten minutes, remove the oil with a soft, clean cloth.

4. Add additional coats of oil as desired. Always make sure to remove the oil from the deep crevices of a piece.

5. Dry overnight. The finished effect is impressive.

Danish Oil

Danish oil is a variation of boiled linseed oil that has had varnish added to facilitate drying. It gives a hard, water-resistant finish, and is available in soft gloss or satin sheen finishes. Although Danish oil does penetrate the wood surface, it leaves a firm, semi-hard layer of oil on top of the wood. This is a great oil finish for any project that will be heavily handled over time, providing both the oil benefits to the wood as well as a soft-feeling, durable surface. Apply straight Danish oil in the same manner as you would a BLO/turpentine mixture, allowing 4–24 hours of drying time before adding the next coat. Use the same safety precautions as you would use with BLO.

Tung Oil

Applying an oil finish.

Tung oil is the hardest of the oil finishes and is most often used as a furniture finish. It dries quickly and leaves a glossy finish on the surface of the wood. While tung oil can take up to 30 days to completely dry, it does harden to a workable finish in just a few hours. The first application of tung oil, which is applied with a rag, brush, or foam pad, will penetrate into the wood surface. All other applications then lie upon the first layer, creating a thin, high-gloss surface above the wood. Tung oil requires multiple coats to build up a strong, long-lasting finish. Follow the directions for use on the can. Use the same safety precautions as you would use with BLO.

Polyurethane Finishes

Polyurethane, whether used as a spray, brush-on, or wipe-on, is a polymer, long-lasting finish that may be either water- or oil-based. It can be used on raw wood as well as on painted projects. This sealer lies on the surface of the wood, not penetrating into the wood fibers like an oil finish does. You can find polyurethane sealers in a variety of finishes, including matte, satin, semi-gloss, gloss, and high gloss.

Advantages: A polyurethane finish can apply absolutely smoothly, without any brush strokes or ridges. You have a wide choice of sheens that are both water resistant and UV protective. This is an extremely hard, durable topcoat for any wood.

Possible Problems: Polyurethane is very fluid when applied and can puddle in the crevices of a project. Thick areas can appear darker or yellow.

Acrylic Finishes

Acrylic finishes retain their crystal-clear look for many years without yellowing. Although it is not as hard a finish as polyurethane, acrylic provides both indoor and outdoor protection, including water resistance and UV protection. Available in both brush-on and spray forms, acrylic sealer is low-odor and dries quickly. You can be working over the acrylic sealer or applying a new coat in less than an hour.

Advantages: Because acrylic sealer is the clearest of all the finishes, it provides long-term protection without distorting color work.

Possible Problems: Acrylic sealers can be affected by the weather or atmospheric environment. Avoid using this finish on extremely hot or cold days or when there is high humidity. All three conditions can cause the acrylic sealer to dry cloudy or white in the crevices of a project.

Wax Finishes

Applying a wax finish.

Grab a can of paste wax or buff wax, also referred to as wood floor wax, when you want the wood to have a wonderful, silky feeling. It’s perfect for walking sticks, canes, wizard wands, jewelry boxes, and chess sets—any wood project that will receive heavy handling during its lifetime. In general, paste wax is applied with a soft cloth or with a soft toothbrush, working an even, thin coating over the entire piece. Allow the wax to dry for about ten minutes, then buff the wax surface briskly with a clean, dry cloth. Multiple thin layers will build up a smooth, semi-gloss finish. Although this method is more time intensive than many other sealers and finishes, it leaves a water-resistant surface that is super-smooth and comfortable when handled.

Advantages: One can of paste wax can last a lifetime. Over the life of a project, you can apply new coats of paste wax to refresh the surface and appearance of a project. It leaves neither an oily nor overly slick finish, making it perfect for any project that will be gripped or held repeatedly.

Possible Problems: Obtaining a deep, smooth finish with paste wax does take a little more time and effort than other finishes. Do not hurry the application of multiple layers when working with paste wax. Instead, allow a day or more between coats to allow previous coats to thoroughly cure. Slow and steady creates the perfect wax finish.

Spray Versus Brush-On Sealers

Polyurethane, acrylic, varnish, and even shellacs are now readily available to crafters as both spray-on and brush-on finishes. Use a spray sealer when you need a fast-drying finish or an intermediate sealing layer between color applications. There are no pans, tubs, brushes, or rags to clean up after you have applied a spray sealer layer. They tend to dry to a reworkable stage within a few minutes to up to a few hours. Use any spray sealer in a well-ventilated area or outdoors. Several light coats of spray sealer are better than one heavy coat, which can take extra time to cure or can cause dripping or allow puddles to form. Turn the orientation of the project with each new layer of spray to ensure that you seal all the cracks, crevices, and undercuts.

Brush-on sealers are often used when you want an even, controllable application. They should also be used in a well-ventilated area. Apply thin coats, brushing the excess sealer out of any deep areas of the work. Brush-on sealers tend to take longer than spray sealers to cure to a reworkable stage, so allow a little extra time to complete a project. Read the instructions on the jar to discover what solvents may be needed to clean the brush after each use.

This is a brush-on acrylic satin finish.

UV Protection

Not all wood finishes or wood sealers add UV protection to your project. Check the can or jar label if you need a finish that can stand up over time to bright, direct sunlight. Polyurethane and acrylic sealers offer the strongest UV protection. Also check the labels for indoor and outdoor use.