Whether you handcrafted a wood bowl or bought an unfinished bowl from a work shop, the bowl will eventually require a finish. Even a decorative bowl needs a finish of some kind to ensure the bowl enjoys a long lifetime, and if the bowl is intended for use in the kitchen a food-safe finish is absolutely necessary. A variety of finishes are available for wood bowls, but food-safe finish or no, even the most durable finish for a wood bowl is not dishwasher-safe.
One way to finish a wood bowl in a food-safe fashion is to use a drying oil, or an oil that penetrates the wood, repels moisture and hardens the wood all at the same time. Two of the most popular drying oils are linseed oil and tung oil. These oils are applied with a paint brush. Food-safe oil finishes, including drying oil, are typically not as durable as some non-safe food finishes, and the application of several coats of oil is usually necessary to protect the wood. However, each application of oil deepens the existing color and grain of the wood, so striking a balance between the desired appearance and protection is usually necessary.
Non-drying oils consist of those food-safe oils that penetrate the wood and repel moisture, but do not harden the wood in any way. Most of these oils are plant products of some kind, such as olive oil and walnut oil. Ordinary vegetable oil can be used in this fashion as well, and although vegetable oil is cheap, it will eventually turn rancid and is therefore not a very good idea. Non-plant oils, such as mineral oil, also fall into this category. Like drying oil, non-drying oils are applied with a paint brush, require several coats and deepen the color of the wood.
Another food-safe finish for wood bowls is wax, such as paraffin wax (the same wax used in wax paper) and beeswax. Waxes are harder than oils to pigeonhole in terms of their qualities. Carnauba wax hardens wood like drying oil, but beeswax has better water-resistant qualities. Like oils, waxes are brushed on, but a wax is solid at room temperature. It must therefore be melted before it can be applied, usually in a double boiler.
If the wood bowl is strictly decorative and will never be used for handling food, other, more conventional finishing techniques can be used, such as using wood stain and then sealing the bowl with polyurethane. Another technique is lacquering, which can be used for creating a decorative, Asian-style wood bowl. These finishes are longer lasting than any of the food-safe finishing ideas described above, but the resulting finished bowl can only be used as a decorative item and not in the kitchen.