As coopers, we are often asked about the different char levels. Mainly, “Why are the higher char levels –  Char #3 and Char #4 – the industry standard?” Much like the genesis of the charred barrel itself, there isn’t one definitive answer. According to our records, the current char level system wasn’t used until the 1950’s. Prior to that, the level of char was determined by the thickness of the char layer. Purchasers of bulk whiskey would request product that had been aged in barrels charred to a certain depth as opposed to requesting Char #1 or Char #4. This is shown at the bottom of this letter dated February 15, 1826, from a Lexington, Kentucky grocer to Distiller John Corlis.

We can see that after twelve months; the Char #1 barrel contains more extractives than the Char #4 barrel. Moreover, between year one and year two, the Char #1 experienced a larger increase in extractive concentration. If more extraction is the goal in your double-barreled product, keeping the char level low on the secondary barrel will benefit the cause greatly. In 95% of the double barrel applications, we are going to recommend a barrel with a light char and possibly a toast if more extractives are needed.

We know that the charred layer of the barrel contains very little flavor due to the intense heat of the charring process. We also know that the char layer, being essentially a layer of carbon, serves as an exceptional filter. As such, some flavor compounds that were brought into solution during primary maturation can be diminished when introduced to a fresh layer of char. See Figure 2 below.