There are numerous misconceptions out there about the wood used in aging alcohol, and hopefully this blog post will clear a few of them up. End grain is the surface of wood that you would see (the rings of a tree) if you cut a tree down. Side grain is the surface of wood that you would see if you vertically split a tree in half up the middle. Wood cells are long and thin, and are oriented vertically in the trunk of a tree so that they can shuttle moisture from the soil to the rest of the tree. Real bourbon barrels were constructed so that no end grain touches the alcohol inside of the barrel. There are two primary reasons for this.
The first is that if end grain came into contact with the alcohol, the alcohol would leach out of the barrel leaving an empty barrel after a few years. Second, and more importantly, end grain exposes the capillaries and has a high ratio of destroyed wood cells vs whole cells. Especially in oak varieties, capillaries themselves and their contents tend to impart an undesirable brown paper bag flavor to alcohol. In addition, the flavor imparted by alcohol passing into and out of a structurally sound cell wall is vastly superior to the flavor imparted by a compromised or broken cell wall where the "guts" of the cell are exposed.
An extreme example of the difference between in tact wood cells (fibers) vs destroyed cell walls is the results derived from soaking a "tea bag" of wood sawdust in alcohol. Sawdust is nearly exclusively made up of destroyed wood fibers and all of the contents of the capillaries. It is widely understood that sawdust is completely useless for adding flavor to alcohol because it produces such foul tasting results. Compare this to the results achieved in a real barrel.
Bottle Aging Staves™ are designed to minimize end grain as much as possible to produce the best results. In every blind experiment conducted by Beyond Barrels where the amount of end grain was the only variable, everybody unanimously chose the product with the least amount of end grain as superior. The ratio of side grain vs. end grain in Bottle Aging Staves™ is high enough that the negative influence of end grain is undetectable to everyone who tested it.