Dear Mr. Wizard,

If I wanted to use oak or beechwood chips in brewing a 5.5 gallon batch of beer, how would I go about it? How many ounces would I use and how would they be handled in the mash or fermentation containers? How long would they be left there? I realize that they would have to be steamed for 15 minutes before using.

Paul A. Borowski
via email

Mr. Wizard replies:

You have really asked two different questions here: How to add oak for flavor and how to add beechwood for aging. Beechwood does not not add flavor. Adding oak chips — which is done in the fermenter, not the mash tun — can add some interesting flavors to your homebrew as well as acting as a surface area to accelerate aging.

Whether using oak for flavor or beechwood to help with aging, the weight of the wood chip is not the most important consideration. Rather, the surface area is the key factor to consider. The flavor from the chip is released into the beer only where the beer and the chip are in contact. You could have a bag of thin oak chips and a bag of thick oak chips that both weigh the same, but the thin chips would have a greater surface-area-to-weight ratio. So the thin chips would add more flavor than the same weight of thick chips.

I recently made some oak-aged hard cider and got an incredible aroma from the wood during the aging process. The barrels I used are about three feet in diameter,
four feet long and contain 50 gallons of liquid. To put this in beer-geek terms, the barrels have about 149 square inches of oak area per gallon of contents. This statistic is the barrel’s surface-to-volume ratio. That’s a good number to keep in mind, since most barrels used for aging wine are in this size range. As the capacity of a barrel increases, its surface-to-volume ratio decreases and the time required for the oak to flavor the contents of the barrel increases.

When I decided to do an oak-aged cider, I had to make a few decisions. To begin with, I had to choose between new and used barrels. I wanted to flavor my cider with oak and nothing more, so I chose new barrels. I then had to choose among several different levels of “toast.” Toast refers to the firing the inside of the barrel receives during the manufacturing process, similar to the toasting or roasting of malt during kilning. I also had an option of interior surface roughness and could buy American or French oak.

I chose American oak, with a medium toast and a “normal” surface roughness. According to the barrel maker, this would give me nice vanilla notes from the toast level, an aroma consistent with American oak. The roughness of the interior would result in a faster release of oak flavors than a barrel with a more polished finish.

To be honest, I felt pretty ignorant when faced with all these options. So I asked, “What barrels are used by winemakers producing aggressively-oaked Chardonnays?” “Most of our customers use American oak with medium-plus toast with a normal roughness,” was the reply. “Very well,” I said, “I’ll buy two of those!”

Most of these same options are available when buying oak chips that are added to the aging vessel. You may also choose used barrels because used barrels may add more than oak flavors. There are many stouts available these days, for example, that have been aged in used bourbon barrels. As a result, these bourbon stouts have complex bourbon flavors. Sam Adams uses port and sherry barrels to age their triple bock family of beers. Used barrels open up a whole world of options that can be explored to create new and interesting beers. If the barrel contained whiskey, most brewers don’t worry about sanitation. Used wine barrels, however, can pose problems and must be sanitized prior to use.

Right now it’s summer, a good time to brew a big beer for the winter. Imagine a strong ale with assertive bitterness, low hop aroma and a full and clean malt backbone. This beer has just finished primary fermentation and the plan is to age it on oak to add further complexity to its flavor. A bag of oak chips with the desired toast has been purchased and the question is how much to add. If the chips are two inches wide, four inches long and 0.25 inches thick they will each provide 19 square inches of surface area (two sides at eight square inches, two edges at one square inch and two edges at 0.5 square inch). Eight of these chips per gallon of beer will give about the same surface-to-volume ratio (149) as an oak barrel. So set aside 43 of these chips for the 5.5-gallon batch of beer.

Chips will float and it is important to keep the entire surface of the chip in contact with the beer during aging. A hop bag weighted with some stainless steel bolts (or some other inert weight) will do the trick. Sterilize the bag, chips and weight with either steam or hot water. I chose to fill my barrels with 195° F water and let the barrels sit for several hours prior to use. Either method will work for sterilization. Some sanitizing solutions will damage the wood and perhaps flavor the beer. Burning sulfur is one method of sanitizing barrels used by winemakers, while using a dilute solution of KMS or Campden tablets is another. I like hot water because there is nothing added to the barrel other than water.

The next step is to place the chip bag into a vessel for the aging process. This poses a dilemma since the chip bag won’t fit into a carboy and a plastic secondary allows oxygen into the beer. The ideal container is a five- gallon Cornelius keg. Place the chips in the keg and rack the beer from the primary into the keg for aging. Try to minimize the amount of yeast carried into the secondary as excessive yeast will impart autolyzed flavors from yeast death over the aging period. The beer can be primed at this time or you can wait until later. Priming at this stage will be easy since the yeast viability is still excellent. If primed later, more yeast will most likely need to be added.

Now it’s time to wait. This is the most important step to oak aging. It is tempting to place the keg in a cool corner and to forget about it for several months. After all, if you pay attention to the beer during aging, the temptation to drink it early may get to you and you will have no beer left after nipping on it for several months. However, if you store the keg where it is too cool, the flavor takes longer to extract. Too warm and the beer suffers because of yeast autolysis. Cellar temperature (55° F) works well for the aging step.

Vigilance and restraint are required during aging. Sample the beer on a regular basis — say once every three weeks — to keep tabs on its progression. The purpose is to prevent the beer from becoming excessively oaky. The oak should add complexity to the beer, but not dominate its flavor. Once the flavor reaches the intensity you desire, you can rack the beer into a second keg or bottle it.

Another variation is to not worry about the oak intensity during aging and to blend the oak-aged beer with a batch of non-oaked beer to produce the desired oak intensity. This is how I treated my cider, which became so oaky after three months in a new barrel that it was hard to smell or taste anything else but oak!

You also mentioned beechwood in your question. Beechwood aging has absolutely nothing to do with wood flavor. The wood gives the yeast more surface area to cling to and helps the beer age. The one brewery I know that still uses beechwood aging goes to a lot of effort to cook all the wood flavor out of the chips prior to use. This process also renders the chips non-buoyant so that they lay on the bottom of the chip tanks during the lagering process. These long, curly chips add a tremendous amount of surface area that yeast settles on during lagering. Diacetyl and acetaldehyde reduction during aging requires yeast and beer to interact, and that is precisely what the beechwood chips do for the brewer. This reactive surface area is similar to the enormous surface area in the human intestine across which we absorb nutrients from food. If the intestine were smooth it would have a much lower surface area than it does with its microscopic convolusions. Beechwood chips give yeast a large surface area where they can hang around and interact with the aging beer.

Although I have no data to support my opinion, I bet any benefit to this practice would be very hard to quantify in a 5-gallon batch of beer. Most chip tanks in the United States are horizontal tanks containing about 60,000 gallons of beer. That’s a lot of beer!

For more of the Wizard's wisdom, pick up the latest issue of Brew Your Own now available at better homebrew shops and newsstand locations.