Food-Safe Wood Finishes: What the Evidence Supports

21 CFR 175.300 sets the terms for resinous and polymeric coatings used as the food-contact surface of articles meant for repeated contact with food. Such a coating must form a continuous film that acts as a barrier between food and the material beneath; the regulation lists the substances it may be made from — tung, linseed and walnut among the permitted drying oils — and limits what the finished coating may give up to solvents in a laboratory extraction test. It regulates formulations and finished coatings. It does not certify a can of finish, and an oil being on its list of permitted ingredients is not a finding that any product made with it is safe for food.

A cutting board is cut into, washed often and soaked repeatedly, so a film on it will be cut through. The Forest Products Laboratory's suggestions for cutting boards and butcher blocks are mineral (paraffin) oil and paraffin wax: they do not go rancid or support microbes, the Laboratory says, but they do not cure either, so they wear away and are renewed. It warns that baby oil should not be used, because it contains ingredients that should not contact food. General Finishes draws the same line in its own range, pointing countertops used for chopping to its butcher block oil rather than its film-forming bowl finish.

• Film finishes. The Laboratory says film finishes are the easiest to clean and resist staining better than oils, but eventually crack, chip and peel; it notes that lead was once used in varnish but that the practice ended long ago in the United States and Europe.
• A maker's food claim, with its cure. General Finishes describes its Wood Bowl Finish — an oil-based polyurethane — as 'food safe when cured', for bowls, cups, spoons and decorative countertops, and gives oil-based finishes 30 days to cure. The claim is GF's, for that product, after that cure.
• Oils. Drying oils such as tung and linseed cure and resist water, but may take several weeks; the Laboratory's advice for oiled utensils is to let them dry thoroughly for several weeks before use. Vegetable oils, it notes, can go rancid and taint food.
• Dishwashers are hard on any wooden object, whatever the finish, the Laboratory says.

• Is tung oil food safe? Tung appears on the FDA's list of drying oils permitted in food-contact coatings, and the Laboratory names it among drying oils for kitchen items. That is not a finding about a particular product — and some products sold as 'tung oil finish' are varnishes made with tung oil; see oils.
• Is polyurethane food safe? General Finishes makes that claim for its Wood Bowl Finish once cured; no general statement covering all polyurethanes was found.
• Is Danish oil food safe? Watco's data sheet for its Danish Oil makes no food-contact statement either way, so none is made here.
• Food-safe stain? None of the stain documents reviewed makes a food-contact claim. Stain is colour under a finish; ask the maker of the specific product.
• Furniture wax? Minwax labels its paste wax harmful or fatal if swallowed; the Laboratory's food-item wax is plain paraffin.
• Shelves, tables and other incidental contact are not addressed by the documents reviewed.

CPSC limits lead in paint and similar surface coatings on children's products and certain furniture to 90 parts per million — a limit on lead, not a general approval of any coating. Beyond that, the statements are makers' own: Osmo says its dried Polyx-Oil is suitable for children's toys under EN 71.3, and Zinsser says its Bulls Eye Shellac suits wood toys and dries to a non-toxic film. Anyone making children's items for sale should read the CPSC requirements directly.