Food Safe Finishes, Part 1 - Oil Finishes
This will be part one of a three part series we will be doing on food safe finishes. In this article, we will begin by covering the oil based food safe finishes which are readily available on the market today. In the next two parts, we will cover wax finishes and blended finishes.
Pure tung oil -
Pure tung oil is a nut extract and is food safe. Tung oil blends (which are frequently found in most hardware stores) can potentially contain unsafe additives. Most pure tung oils are labeled as such, but always check for any warning labels on the product you wish to use. Tung oil requires at least several applications to build a sufficient surface, but is the most durable oil finish that you will find. An additional benefit: tung oil can be sanded or buffed to produce nearly any sheen.
Raw linseed oil -
Raw linseed oil is an extract of flax seeds and is food safe. Boiled linseed oil, however, contains additives which render the product unsafe for usage with foods. The oil produces a dull glossy surface with just a few applications, but is not very durable or water resistant. Additionally, most woods will darken heavily after several years if linseed oil is continually reapplied (which must be done repeatedly since this finish is non-durable).
Mineral oil -
Mineral oil is a petroleum extract which is food safe. It is sold as a laxative, and is readily available at nearly any drug store. It is easy to apply, dries quickly and is very inexpensive. The only drawback to mineral oil is that it must be continually reapplied unless a more durable surface (such as wax) is added to keep the oil from evaporating from the wood, and to keep water from penetrating into the wood.
Walnut oil -
Walnut oil is extracted from walnuts and is food safe. It is available in many grocery stores (usually near other salad oils), and sometimes in woodworking stores as well. Like mineral oil, it is easy to apply and dries quickly, but must have a more durable surface applied to it to reduce the evaporation of the oil and to reduce the penetration of water into the wood.
Commercially available oil blends -
There are other oil based finishing products, such as Waterlox and Behlen's Salad Bowl Finish that are available on the market today. Just about all are one of the previously mentioned oils (tung oil, linseed oil, mineral oil or walnut oil) which have either been blended together, or which contain additives to improve water resistance, wear resistance and/or ease of use.
Plant oils -
Plant extract oils, such as vegetable oil, peanut oil, and soybean oil (to name a few) can be used to produce a food safe finish, but only temporarily. All of these oils will eventually become rancid with time, creating a habitat which becomes ideal for the growth of bacteria. While it may be tempting to use these oils since they are readily available in most homes, it is not recommended, and can be potentially unsafe.
If you should decide to use an oil based finish, remember that although they produce a beautiful surface initially, most will have to be reapplied regularly to maintain the finish. The only exception to this rule is pure tung oil, which will provide a hard, durable finish after several applications. To really get the best durability out of items you finish with oil, a wax finish should be applied afterwards to increase wear resistance. We will cover this more fully in next month's newsletter article!