For thousands of years, wood finishes have been evolving to suit a myriad of situations. But if you want to use a finish for a surface that will be coming into contact with food, it’s imperative to use one that’s non-toxic. And in the case of items like chopping surfaces that wear down quickly, ease of serviceability will also be key. Let’s look at some user-friendly options that will keep our woodenware, and bodies, in good shape.
Tree nuts and other plant seeds have been providing an array of oils for millennia. Some of these are suitable for finishes on wood, stone, and even metal. The preferred oil is one that is classed as a drying oil—one that doesn’t remain fluid, but rather cures to form a film. It’s this film that affords the oils the durability of water resistance, and in the case of food contact items, a nobler barrier to micro-organisms looking to set up shop. Also a real risk with using non-drying oil is the fact that it offers an easy food source for microorganisms, and becomes rancid. Rancid oils are toxic, so as tempting as it is to douse your wooden cutting board with olive oil, don’t do it.
Going back many centuries, the Chinese discovered that the nut of the tung tree (which is native to China), had some interesting properties. Classed as a drying oil because it forms a tough film, it was used for waterproofing ships, stone, and rope. In more modern times, Tung oil is also offered up in polymerized form to expedite drying. The addition of solvents and metal driers renders the finish toxic, and these altered versions of oils should be avoided for food contact items. Just look for terms like “100% pure” or “natural” to be sure it’s food safe. In addition to Tung, other drying oils include the once ubiquitous linseed, safflower, soybean, and my favourite, walnut. Of these, tung and linseed are the most durable outside, but both will attract mould, so you have to be diligent about keeping the surfaces clean.
So let’s say that outside you have a wooden shelf on your barbecue, and you need to protect it from the elements while also being able to safely place food on it. Several coats of tung oil will do the trick, as the oil forms a highly elastic surface that holds up when the wood moves from swings in humidity. To apply it, sand and clean the surface before using a small cloth (torn from an old t-shirt) to saturate it with the first coat of oil. Let this soak in for 20 to 30 minutes before wiping off any excess. Oils have a tendency to ooze a bit from wood pores even after wiping, so be sure to periodically check the piece. If you notice little beads of oil, wipe them off. In one to three days, depending how ambient conditions affect curing, you can apply the next coat. Aim for three coats as a minimum, sanding lightly between coats to remove any upstanding fibre. When sanding, the finish that sloughs off should be dusty, not gummy, to indicate adequate drying. Remember to wipe the surface well to remove dust between coats.
Oil and wax
Indoors, we have a neat option that incorporates oil into its making. By heating wax and oil together, we can easily make our own paste-wax. Into the top of a double boiler, place one part beeswax with about five parts of your choice of drying oil. Some folks use mineral oil, but it doesn’t dry, and it can attract dust. Heat the blend until the wax is liquefied enough to stir into the oil. I then pour this mixture into shallow wide-mouthed mason jars. Wad a piece of cheesecloth as an applicator. Warming the cutting board, chopping block, salad bowl, or wooden spoon before you begin to apply the paste will make it flow more easily and saturate more deeply.
The advantage with a paste-wax finish on a cutting surface versus an oil film is that the former is a very “casual” finish that takes wear, whereas the latter shows every knife mark. The drying oils don’t behave quite the same once they’ve been married to wax, so you can do quick touch ups and have your wooden item back in service straight away. Of course, the longer you can leave a finish to harden after buffing it out, the more fortified it’ll be. Experience will guide you as to how many coats to use here.
Sean Ledoux is a designer/master fine craftsman working with wood and other found media to create unique furniture. Having diversified skills helps support studio life in North Bay, ON. www.seanledouxfurniture.com