Oil Finishing for Butcher Block Tops
While traditionally the butcher blocks were meant to be used for chopping, cutting and slicing meats, nowadays we find that this strictly functional role is slowly left behind and the butcher-block tops are mainly employed on the grounds of the visual effect that wood generates.
In such instances, the wood is commonly finished with polyurethane-based or water-based varnish, acrylic lacquer, stain, or any other sort of build-up finish, which both seals the wood and creates the desired looks. For those few left cases of butcher-block tops that are actively used for food preparation, however, the range of finish choices is substantially narrowed down to the oil finishes, which raises a bit of a problem.
The problem is, the oil finishes are not finishing actually, but more of a continuous treatment to the wood. As soon as the oil is applied onto the wood surface, it will reach, due to capillarity, to the wood core, which will eventually leave the surfaces dry and hence, a new coat of oil will be required. Routine maintenance becomes, therefore, part of the deal since, if the treatment is not carried out periodically, the wood will start exchanging moisture with the environment and, consequently, the wood may swell or warp in an excessively moist climate, or, conversely, crack if the atmosphere is rather dry.
Regular application of oil thus being the only way to secure a long, functional life for your butcher block, it is usually carried out monthly during the first year and once every 4-5 months ever after. Particular circumstances, however, will further adjust the frequency. Wood species with a higher porosity such as beech or oak will require a more frequent treatment than maple, black locust or other similarly tight-grain wood. The pace of wear and tear is another factor to influence how often the re-oiling is to be performed. As the butcher block is sanded down at times in order to remove cut marks and scratches, a new coat of oil must follow each sanding. The blocks extensively used on a daily basis are usually sanded down every couple of weeks or so and hence, the re-oiling would follow the same frequency pattern, too.
When choosing the oil finishing, it is important to select a food-grade inert oil, like walnut oil, tung oil or food-grade mineral oil. Vegetable oils, although safe in contact with foods will eventually go rancid and impart undesired odor and taste. Others, such as the Danish oil, although stable are not suitable for food contact. For increased water-repelling and stain protection properties, mineral oil can be heated, mixed thoroughly with beeswax and immediately applied, the resulting mixture being something in-between a penetrating and a build-up finish.
The oil is applied extremely easy, by pouring it onto the wood surface and then smearing it with a paintbrush, rag or sponge. Never worry about applying too much oil, especially during first time session. When the oil is indeed too much, it will stagnate onto the wood surface for many days and would have to be wiped off with a clean, dry rag or paper towel, but it will take time for the wood to achieve this level of oil saturation. Most often, the oil will go into the wood fiber within a 2 to 24 hours interval. The speed at which the wood will suck the oil in will vary with the type of oil used, the wood species and the grit the wood was sanded at. Woods with a naturally oily fiber, like walnut or black locust, will absorb the finish at a slower pace and so will do the wood polished down to a very smooth surface. Walnut oil generally gets absorbed slower than the mineral oil but faster than the tung oil, which also tends to dry the wood and sometimes raise the fiber.
Three to four coats of oil are required before installation on both topside and bottom one, particularly insisting on the end-grain area, where the wood pores are open wider and the oil is absorbed about twice faster. Following the installation, the re-coating is done on the topside only.
Adrian Laza, Lafor Wood Products. https://www.hardwoodcountertops.com