Before a single stave is bent into shape, it spends more time simply sitting outdoors than it will spend as part of almost any finished barrel-making step that follows. That waiting isn’t wasted time. Natural wood seasoning, the outdoor drying of freshly cut oak staves, is one of the few stages in cask making where there’s no shortcut that doesn’t show up later in the glass.
This article looks at what natural wood seasoning actually does to the wood, why it takes so long, and why the extra time is worth it compared to faster alternatives.
What natural wood seasoning actually is
Once oak logs are split into rough staves, that wood is still too wet, too tannic and too unstable to build a barrel from. Natural wood seasoning is the process of stacking those staves outdoors and leaving them exposed to the elements, rain, sun, and temperature swings, for months or years before manufacturing begins.
This is different from cask seasoning, which happens later and involves filling an already-finished barrel with sherry wine. Wood seasoning happens first, to the raw staves, before the cask even exists.
Why time matters: what happens to the wood while it dries
Two things happen to a stave during natural seasoning, and both take time to complete properly.
First, moisture content drops. Freshly cut oak needs to dry down to a moisture level the wood can hold its shape at, roughly around 12%, before it’s stable enough to be shaped and toasted without cracking or warping.
Second, and less obvious, the wood’s harsher compounds break down. Rain and sun wash out some of the greenest, most bitter tannins, while natural microbial activity in the wood stack helps soften what’s left. The result is oak that gives a rounder, less aggressive character once it eventually holds spirit, compared to wood that hasn’t had time to go through this.
Natural seasoning vs kiln drying
Not every cooperage seasons its wood naturally. Kiln drying, where staves are dried in a heated chamber over a matter of weeks rather than months or years, is faster and cheaper, and some producers use it for that reason.
The trade-off is in the wood itself. Kiln-dried staves tend to retain more of the harsh tannins and bitter compounds that natural seasoning gradually removes, and can be more prone to shrinkage cracks once shaped into a barrel, since the drying happens faster than the wood’s structure fully adjusts to. Natural, outdoor seasoning takes longer precisely because that gradual adjustment, and the slow leaching of harsh compounds, can’t be rushed without losing the result it produces.
How long is long enough
Industry practice varies, with outdoor seasoning periods ranging anywhere from a few months up to two or three years depending on the cooperage and the intended use. At Tonelería Juan Pino, staves are seasoned outdoors under the Andalusian sun for at least 18 months before manufacturing begins, and every batch of wood is inspected before it ever reaches that stage: staves with knots, insufficient thickness or an irregular grain are rejected rather than seasoned and used anyway.
The longer end of that range tends to matter most for spirits with long maturation programmes ahead of them, where a harsher, less-seasoned stave would have more time to overcorrect a spirit’s profile than a well-seasoned one.
Why this stage shapes everything that follows
Wood seasoning happens before toasting, bending, or any of the other steps covered in our step-by-step cooper’s guide, but its effects don’t stay confined to that first stage. A well-seasoned stave takes heat and toasting differently than an under-seasoned one, and carries a different set of compounds into the spirit for as long as the cask is in use.
Skipping or shortening this stage doesn’t just risk a rougher-tasting spirit; it also increases the odds of cracking or leaks once the barrel is in service, since insufficiently seasoned wood hasn’t fully stabilised before being shaped and heated.
Frequently asked questions
How long does oak need to season before it can be made into a barrel?
It varies by cooperage and intended use, typically anywhere from a few months to two or three years. At Tonelería Juan Pino, staves season outdoors for at least 18 months before manufacturing begins.
What’s the difference between wood seasoning and cask seasoning?
Wood seasoning is the outdoor drying of raw oak staves before a barrel is built. Cask seasoning happens afterward, once the barrel is finished, and involves filling it with wine to prepare it for spirit maturation.
Is kiln-dried oak worse than naturally seasoned oak?
Kiln drying is faster and cheaper, but tends to leave more of the harsh tannins and bitter compounds that natural seasoning gradually removes, and can leave staves more prone to shrinkage cracks once shaped.
Do you have questions about how we season our oak?
At Tonelería Juan Pino every stave is seasoned outdoors under the Andalusian sun for at least 18 months before it becomes part of a cask, with every batch inspected before manufacturing begins. If you want to know more about our wood sourcing or seasoning standards, our team is ready to help. Write to us here.