sapwood and heartwood is the same. Depending on the species, these tubes, or "pores" may be more or less pronounced, which can give rise to finishing problems.
In each hardwood species, the pores arrange themselves into one of three possible configurations. The first is called ring-porous. That means that the pores are concentrated along the newest growth region in the earlywood portion of the growth ring. This pattern is typical for many, but not all, hardwood species grown in temperate climates with distinct seasonal patterns, such as North America. A few examples are red and white oak, black walnut, white ash, shagbark hickory, chestnut, and Osage orange. In general, these ring-porous species benefit from using a filler as part of a glossy, film-building finish. Diffuse-porous pattern means that pores of identical diameter appear throughout the entire growth ring. It makes it very difficult to discern ring patterns. This pattern is very common in tropical hardwoods that can grow almost continuously throughout the year. These woods can include koa, cocobolo and Gaboon ebony. Domestic examples are hard maple, boxwood, and basswood. These species generally do not require a filler. The third category of pore distribution is halfway between the first two classes. It is called either semi-ring-porous or semi-diffuse-porous. The characteristic of this class is that the pore diameter decreases as they march into the latewood portion of the ring. Examples of this class are persimmon, Spanish cedar, holly, cherry, and butternut.
Finishes for Carvings
Just as we talked about how the wood pores can affect the finish placed on the wood, here are some finishes that we can use to put on our completed carving.
Beeswax is easy to apply, dries quickly and is food safe. It should be reapplied yearly and has low durability.
Lacquer can be brushed or sprayed on. It dries quickly but the vapor is harmful and combustible. It is not food safe. Second and/or third coats can be applied but be sure the previous coat is completely dry before applying the next coat. Contact with water is detrimental to the finish. Varnish is a very durable finish. It is not food safe, but it can be great for walking sticks. It is slow drying so make sure the environment is relatively dust-free. Brushed on polyurethane can make the carving look plastic.
Shellac dries fast and gives the wood a warm amber color. It is a universal sealer so it can be used under any finish.
Oil Finishes are brushed onto the wood allowing the oil to penetrate the wood then wiped off with a rag. Drying time varies with the type of oil finish used. Linseed oil can take up to 14 days to dry. It is not food safe. Tung oil is very durable but takes up to a month to dry between coats. Walnut oil is easy to apply and is used to finish bowls and utensils coming into contact with food. Let the oil soak into the wood for a few hours to overnight. It should be reapplied periodically as needed. Mineral oil is also used for treating utensils and bowls. Just make sure it is safe for human consumption. Danish oil comes in a variety of colors. It is wiped on then off after a period of time. Drying time is up to 24 hours.
Acrylic paints are very familiar to those of us who use them to color our carvings. It is not food safe so care must be used when the carving may come into contact with children. Since the paint can absorb into the wood some people will seal the wood with boiled linseed oil or a diluted lacquer/sanding sealer.
Watercolor paints could be applied to your carving if you wish to keep a lot of the woodgrain visible and want a subtle color to portions of the carving.
Cooking oils should not be used to finish bowls or utensils. While mineral oil and walnut oil is great to use, using cooking oils such as olive oil, canola oil or vegetables oils will go rancid and start to smell after a while causing the carving to become gummy and gross. They can also deteriorate your carving and attract bugs.
When disposing of rags used in wiping finishes off of the carving, I will place the rag in a closeable plastic bag and add a cup or two of water and seal the bag. I want to prevent the possibility of combustion. It is also placed outside of my workshop/house...just in case.
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