Food Safe Finish Considerations
It’s about more than what’s in the bottle
What finishes are food safe? This is one of the most common questions and one of the most hotly contested topics in the woodworking world right now, and the answers range from “all of them” to “none.” Rather than give you a list of “safe” or “not-safe” products, I’m going to walk you through a basic understanding of food safety regulations in the US, and some other considerations that can help you choose the right finish for your circumstances.
First, it’s important to understand that the FDA (Food and Drug Administration) doesn’t approve products, they regulate them. The FDA hasn’t tested every available brand and product, they’ve just set up guidelines for determining whether a “food safe” label can be used. There’s an inherent level of risk when using any finish product, whether it has that label or not; but it’s also true that there’s an inherent level of risk in driving to work each morning. That’s just part of life.
Now back to finishing. When two surfaces come in contact, it’s pretty common for a phenomenon called “leaching” or “blooming” to occur. At a microscopic level, each surface will pick up molecules from the other. The longer they’re in contact, the more molecules will be exchanged. In woodworking terms, that means your morning cereal is picking up very tiny amounts of the finish off the surface of your bowl every time you use it. In order for a finish to be considered “food safe” by the FDA, the molecules that are leached into food from the finish must either be totally safe to consume, or they must be leached in such tiny amounts that your body can easily and safely flush them through.
According to the FDA database of approved ingredients for finishes and adhesives, all modern unpigmented finishes (ones that don’t contain lead, mercury or toxic colorants) are technically considered food safe IF they are applied in reasonable amounts and allowed to cure properly. The FDA’s list of approved ingredients includes every solvent, hardener, drier, oil and resin commonly available on the market. So in a way, any finish that only uses these ingredients and that cures properly according to the FDA’s tests can be considered food safe.
An important thing to note here is that “curing properly” in this context takes much longer than the 24 or 48 hours on the back of your bottle of finish. Those numbers usually represent how long it takes for a finish to cure to optimal hardness, or durability. After 24 hours, you’re not going to leave fingerprints if you touch it. But just like a newly finished piece will keep a funky smell for days or even weeks past the cure time on the bottle, it’ll also continue to leach small amounts of finish and additives onto anything that touches it. The standard guideline is to let a finish cure for 30 days before it can be considered food safe, meaning that the tendency to leach has dropped down to safe levels.
With Federal regulations in mind, here are a few other things to consider.
Avoid oils that can go rancid
Some oils, like vegetable oil and olive oil, will go rancid if they’re left at room temperature for a long time. There’s no way to clean rancid oil out of wood, so using these oils as finishes is a recipe for disaster.
How long can you wait?
As mentioned above, it’ll take 30 days for most finishes containing solvents or driers to cure to food safe levels. If you’ve got the time, that leaves your options wide open. If you don’t have the time, it’s best to choose a finish that is made from pure ingredients that are safe to consume as is (such as tung oil, beeswax, shellac, or any other finishes from this article). Some of these finishes still have long curing times before they harden up (and some of them never harden), but since the raw finish is safe to consume, leaching from an incompletely cured finish is less of a concern.
How durable does it need to be?
Different applications can warrant different answers to this question, and it doesn’t always make sense to pick the hardest, most durable finish for every project. For example, while a coat of polyurethane might make perfect sense on a salad bowl, putting a hard, chip-prone finish on a cutting board can be dangerous. If your finish is going to take abuse from a knife or regular pounding, it’s likely that chips of finish will break off and get into your food in much higher quantities than typical leaching, so it’s best to choose a consumable finish in those cases.
If you’re making bowls or platters, though, “softer” finishes like some oils and waxes will wear, wash or dissolve off much more quickly than a hard finish, or they might leach right into your food and give it a funny taste or smell (walnut oil especially will leave all your salads smelling a little nutty). If the finish is consumable, the leaching isn’t a safety concern, but it will need to be replenished regularly. Some people like the process of caring for wooden objects, but for others, the idea of having to oil their salad bowl every month is a turn-off. If you have the time to let a finish with solvent or drier cure properly, it might be just the thing your customer is looking for.
Am I going to be safe when applying this?
This is the part where you get to be really honest with yourself about your own attitudes and practices. While most finishes are safe after they’ve cured properly, many are very toxic when they’re wet. Uncured finishes with solvents and hardeners let off toxic fumes and some toxic additives can be absorbed through your skin. If you know that you’re not going to take the time to get out a respirator and put on some gloves, then don’t use those finishes.
How hot is the finish going to get?
Different finishes have different tolerances for heat. Especially when finishing cooking spoons and spatulas, check the safety labels on the back of a bottle of finish to make sure that the finish wont melt or disintegrate at high temperatures.
Is the object itself food safe?
I know this is a discussion about finish, but paying attention to the shape you’re making is just as important when making an object safe to use with food. Avoid creating sharp inside corners, grooves, and other nooks and crannies for bacteria to grow. It’s also worth avoiding soft and extremely porous woods for the same reason.
Full FDA Resource:
Bob Flexner article recommending all finishes: