Board Butter

WHAT IS BOARD BUTTER?

“Board butter” is a blend of non-toxic wax and oil to make a food-safe finish for wooden kitchen implements – cutting boards, spoons, bowls, and so on. You can uses waxes and oils by themselves for this purpose, but the combination of the two makes the finish more attractive and durable. The oil soaks into the wood, accentuating the wood grain. The wax helps keep the oil from leeching out and creates a sheen. Both protect the wood from water and food juices.

Traditionally, board butter is made with mineral oil, but you can use a variety of other food safe-oils, such as coconut and walnut oils. You can also use “drying” oils such as linseed oil and tung oil. These offer an advantage in this application because they eventually cure to harder and more durable versions of themselves. This, in turn, produces a harder and more durable finish for kitchen utensils. In fact, these board butters are only one ingredient away from being a hardwax finish. Add a little hardening resin, and you’re there.

However, there is also a disadvantage – you shouldn’t use the wooden utensil immediately because these oils don’t become non-toxic (technically, food contact safe) until they are fully cured. You also have to be careful to get raw oils with no additives. “Boiled” linseed oil, for example, includes chemicals called driers that speed up the curing process. These are often toxic. “Partially polymerized”* oils may be okay as long as they have no driers or other toxic additives.*

RECIPE

In our board butters we used raw linseed and tung oils because they are “drying oils” – unlike mineral oil, they eventually cure to harder and more durable versions of themselves. This, in turn, produces a harder and more durable finish for kitchen utensils. In fact, these board butters are only one ingredient away from being a hardwax finish. Add a little hardening resin, and you’re there.

Raw Plant Oils

After some experimentation, we settled on a 6:1 ratio oil to wax:

• 6 ounces (170 grams) raw tung or linseed oil
• 3/4 ounce (21 grams) beeswax
• 1/4 ounce (7 grams) carnauba wax

Mineral Oil

When making board butter with mineral oil it came out a bit thinner so we used less oil at a 4:1 ratio oil to wax:

• 4 ounces (113 grams) Mineral Oil
• 3/4 ounce (21 grams) beeswax
• 1/4 ounce (7 grams) carnauba wax

Put the ingredients in a glass or metal container, and place the container in a hot water bath or double boiler until the waxes have melted, stirring occasionally. Warning! Both the oil and the waxes are flammable. Use an electric burner or hot plate; do NOT heat over an open flame. And do not heat above the temperature of the boiling water (212 degrees F or 100 degrees C).

Application

This recipe cools to a fairly hard “paste wax” consistency. You have to work the surface a bit to get it soft and buttery, but once you do, it spreads easily. Since I was covering an end-grain cutting board in the video – and end grain sucks up a finish more so than long grain -- I applied three coats, buffing between each coat. I also gently warmed the cutting board with a heat gun before each buffing. This lowered the viscosity of the butter and helped it to soak in.

CURING

How long does it take the finishes to cure? Both oils react with oxygen as they dry, and the wax limits their exposure to air. This extends their curing time to about twice what it would take the oils alone to cure. Allow 4 to 7 days for the linseed oil board butter, and about twice that for the tung oil.

SHELF LIFE

What sort of shelf life can you expect from this finish? Since the oils cure upon exposure to air, you have to keep the board butter in an airtight jar or can. It’s also wise to keep it out of the sunlight. Do this, and you can expect a shelf life of six month to a year. Refrigerate the butter, and you can extend that up to two years. If you’re worried about the linseed oil going rancid – and it may, especially in a warm climate – add one or two drops of Vitamin E oil. This retards the oxidation process that causes rancidity, but surprisingly it does not affect the curing process. And if you’re worried about the about the linseed oil going rancid in the cutting board, don’t be. Once it’s exposed to light and air, it will cure long before it has a chance to go rancid.

COMPARISON

Were there noticeable differences between the tung oil and linseed oil butters once applied? As you can see in the video, there were almost none at all. Both warmed the color of the wood and produced a slight sheen once they were buffed out. I attribute this sheen to the carnauba wax rather than the oils – the mixes I tried without carnauba were considerably less shiny.

The one noticeable difference was that the tung-oil-coated surface of the board felt more oily than the linseed oil surface. This is probably because tung oil contains some tree resins, while the linseed oil has none. These resins are what cause the tung oil to cure more slowly. It remains tacky longer, but the tackiness eventually goes away as the resins dry. And because tung oil is not considered non-toxic until it’s cured, that tackiness may be a handy indicator. Once the tackiness goes away, the utensil is likely safe to use.

DURABILITY

One last question: How long will this finish last? Conventional board butter, made with non-drying mineral oil, has to be renewed from time to time depending on how it’s used and abused. Both the linseed oil and tung oil board butters are much more durable. And when they begin to look worn, you can either renew them with more board butter or just paste wax.