The practice of ageing brown ales in oak casks has likely been around since soon after the introduction of hops to brewing, many centuries ago.  Before the days of hops beer would be oxidised to malt vinegar.  With the arrival of hops, brewers found that beers were better preserved, and even if they still turned acidic stored in oak, it took some months and when it happened, the tang was from the much more acceptable, tasteless and odourless lactic, which is produced by the action of anaerobic bacteria called lactobacilli. 

Even with the advent of paler malts, most aged beers have remained brown, as in the right amounts the pairing with background caramel and malt flavours found in stronger brown ales is far more interesting. Some variants do not see wood but instead get a light tang from the use of an open cooling vessel, with some exposure to ageing in steel, leaving them less complex. 

The examples that oak-aged beers that survived beer’s dull, homogenising, 20th century of uniformity were typically aged for up to two years in temperature-controlled cellars, eventually being blended with fairly fresh beer of the same type to create a skilfully complex balance.  Most of these were located in East or West Flanders, the westernmost part of Belgium. 

Flemish Old Brown (or Red Brown)

The shared characteristics of the aged brown and red-brown ales (5.5-7.0% ABV, from respectively East and West Flanders is that of a sampling strength brown ale with a distinct lactic tang.  Buttery caramel is fine, lightly sherried notes are allowable but any hint of vinegar should be barely perceptible.  The beers are aged in an oak tun (foeder or foudre) for between six and twenty-four months, at which point the brewer or an expert blender will mix the contents of two or more together and prepare the beer for bottling, usually by filtering and adding a small amount of unfermentable sugar.  Yeast is not added to the bottle as its job is already done. 

Other oak-aged ales

While a few oak-aged pale ales have been produced successfully, experience continues to suggest that it is sweet brown ales of sampling strength and darker beers of sipping strength that gain most from these efforts.  More experienced brewers in the field suggest that for the most positive results oak-ageing needs to occur for no less than six months and usually no more than two years.  One or two other heritage examples exist of blended beers featuring one aged in oak.  Recent years have seen brewers in many countries experimenting in reviving the arts of ageing and blending, some going to extraordinary lengths to build up a stock of oak casks and learn the skills and pitfalls of this ancient craft. 

Wood-aged ales

One of the common themes to the older arts of beer making, such as the deployment of microorganisms other than saccharomyces yeast in fermentation and conditioning, is that the phrase “not fully understood” crops up quite often.  This has not stopped some brewers believing that if you pitch netted bags of wood chips into a beer for a few weeks, it will mimic oak-ageing, because some recent scientific paper said it did.  Many tasters do not believe that is correct.  For now, such beers are termed, by convention, wood-aged. 

Barrel-aged ales

A novice may be forgiven for thinking that a barrel-aged beer will have been put in a barrel for the purpose of ageing.  This is not correct.  It means that a beer has been put into a barrel that previously contained some form of spirit or strong wine.  The effects of this depend to a significant extent on what kind of spirit had been there and how much remained.  Leaving a gallon of single malt in an old cask will certainly add pep to a beer, though whether this is any greater in quality or quantity than it would be were the same amount of single malt simply poured into the beer from a bottle is unclear.  Doing the same with casks formerly used for wines, fortified or otherwise, is far more hit-and-miss.  If the lees of old wine remain in the cask when the beer is racked into it, the result can be uniquely vile.  The jury is still out on whether or not beers racked into drained and dried wine casks develop characteristics from the action of residual wine yeast lodged in its walls.