Mineral oil for cutting boards

Overview

Mineral oil is a refined petroleum oil. The white, odourless, USP-grade kind sold as cutting board oil never polymerizes, so it never forms a film: it soaks into the wood and stays liquid. The USDA Wood Handbook says nondrying oils penetrate wood but do not cure, and that mineral oil, being petroleum-derived, is not prone to mildew or to harbouring bacteria the way vegetable oils can be. Wikipedia notes food-grade mineral oil is popular for boards, countertops and bowls. It is the cheap default for kitchen boards.

Pros

• Very cheap, easy, and always available.
• Does not go rancid and does not need curing; the board is usable at once.
• Colourless; deepens grain a little.
• Easy to renew and cannot fail by tackiness, the usual hazard of drying oils.

Cons

• No hardening or film; protection is mostly a temporary water barrier, so reapplication is routine.
• Petroleum-derived; some users prefer plant-based oils (Walnut oil and other food oils).
• Wikipedia notes some oil may be picked up by food and ingested (the claim is flagged there as needing a citation), and mineral oil has a laxative effect at dose; the amounts involved from a board are small but not documented here.
• Nondrying oil blocks later film finishes and glue-ups on the surface.
• Not suited for furniture or anything that needs durable protection.

Suitability

A good choice for Hard maple, European beech, European walnut, Black walnut and Black cherry boards, butcher blocks, bowls and utensils. The Wood Handbook says film finishes perform poorly on cutting boards, and that a simple option is melted paraffin (canning wax). Not for outdoor or high-wear furniture. For end-grain boards, apply liberally to the ends (Finishing end grain).

Coats and application

Wash and dry the board; sand to 150 to 220 if rough (Sanding schedule). Warm the oil slightly if you like, pour or wipe on a generous coat, let it soak for several hours or overnight, then wipe off the surplus. Repeat until the surface stops absorbing, then re-oil monthly or whenever the wood looks dry. For a better water barrier, follow with a beeswax and mineral-oil blend such as Howard's Butcher Block Conditioner (USP mineral oil with beeswax and carnauba), which the maker says also helps repair knife marks.

Compatibility

Mineral oil is compatible with waxes (Beeswax and carnauba), and many board products are oil-and-wax blends. It is not compatible with drying-oil finishes or varnish: oil that is still in the wood interferes with cure, and Tried & True says not to use mineral-oil polishes before or after its products (Polymerized linseed oil (stand oil)). Do not use it as an undercoat for film finishes; for a different finish later, the board needs thorough cleaning back to bare wood.

Care and repair

Re-oil whenever dry. Wash with mild soap and water, dry upright, never soak. Light scars can be sanded and re-oiled. There is no film to strip.

Safety and environment

Mineral oil does not cure, so it lacks the oxidation chemistry of drying oils. The USDA Wood Handbook, however, warns about rags wet with "any other oil" as well as oil-based stain and urethane, and no source opened for this entry clears mineral-oil rags specifically; handle any oily rag per Oily rag safety, and keep rags from drying-oil blends away from the rest.

Food contact claims: 21 CFR 172.878 (as published by Cornell LII) covers white mineral oil with USP-type specifications as a permitted food-use substance; that is a regulation about the oil as a material, not an approval of a particular finished board. Howard's pages call their product USP food-grade, state that it exceeds FDA requirements for direct and indirect food contact, and say it will never go rancid and has no contact with nuts, gluten or other allergenic materials. Those are the manufacturer's statements. The Wood Handbook advises checking the label, the manufacturer or FDA for any food-item finish. See Food-safe finishes. Buy labelled USP or food-grade oil, not motor or machine oil.

Related

• Walnut oil and other food oils: plant-based alternatives.
• Beeswax and carnauba: waxes to seal the surface.
• Food-safe finishes: how to read claims.
• Finishing end grain: boards and end-grain soak.