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Abstract

Why was the work done: The reduction of maturation loss is a significant opportunity for increased revenue in aged spirits and varies through several factors. This work aims to better understand maturation loss by isolating and measuring spirit flow through wood.

How was the work done: Bourbon stave disks were fabricated by computer numeric control milling and loaded into a sealed module consisting of flanges holding the stave disk over a liquid filled pipe. The modules were filled with new make spirit at 50, 62.5 or 70% ABV, with either liquid or vapour contact with the stave disk. Further, the grain angle was measured for each sample. Samples were weighed each month to measure flux through the wood, with measurement of initial and final ABV and liquid mass to differentiate between ethanol or water loss.

What are the main findings: The initial alcohol content had a statistically significant (p value ≤ 0.05) effect on spirit diffusion, with the highest initial alcohol content exhibiting a 6.9 g reduction in total mass loss over the initial alcohol content. Based on the change in alcohol content, the change in mass loss is attributed to increased water uptake. Liquid versus vapour contact showed similar monthly rates of loss of mass and a statistically significant difference in total mass loss, though the magnitude of the difference is small (5.2 g, p value = 0.049), due to increased ethanol loss with liquid contact. Grain angle had no significant effect on spirit diffusion. A predicted average annual liquid loss of 1.2 ± 0.3% was calculated for non-leakage losses from a standard bourbon barrel (200L) matured in Kentucky.

Why is the work important: While the transport of water and alcohol through solid wood has been previously observed, this is the first study to investigate the diffusion of high proof alcohol through undamaged barrel staves. Maturation loss is a complex, unavoidable, and important aspect of ageing spirits, and this work establishes a lower level for maturation loss for spirit matured in Kentucky, USA.

Document Type

Article

Publication Date

2026

Notes/Citation Information

© 2026 Chartered Institute of Brewers and Distillers

This is an open access article distributed under the terms of the creative commons attribution-non-commercial- no-derivatives license (http: // creativecommons.org/licenses/by-nc- nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed or built upon in any way.

Digital Object Identifier (DOI)

https://doi.org/10.58430/jib.v132i1.87

Funding Information

This work was supported by Suntory Global Spirits and the James B. Beam Distilling Company. The charred white oak staves used in this study were provided by the Independent Stave Company (https://www.independentstavecompany.com/).

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