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Scottish scientists reduce ‘angel’s share’
A team of scientists at Edinburgh Napier University has received an award for developing a whisky barrel that reduces the share of spirit lost to evaporation, known as the “angel’s share”.
As much as 20% of the contents of a whisky barrel can be lost to the angels depending on the length of time it spends ageing (Photo: Wiki)
Without adding any other material like glue to the wood, the team of scientists from the university’s Centre for Timber Engineering were able to build a barrel that reduces evaporation without compromising the quality of the whisky.
The scientists, led by professor Abdy Kermani, were awarded on behalf of Napier University along with 21 other higher education institutions as recipients of The Queen’s Anniversary Prizes for Higher and Further Education.
Professor Kermani told The Herald: “We worked using the existing cask and improved that so that the reduction was at an absolute minimum.”
As much as a fifth of the whisky in a barrel can be lost through evaporation depending on the length of time it spends ageing.
It is not yet fully known how much whisky the newly developed barrel will save from evaporation given that the whisky it contains will be aged for 10 years.
The research into barrel construction was funded by global drinks producer Diageo, which has a large stake in the Scotch whisky industry, owning the Johnnie Walker and Bell’s brands.
A Diageo spokesman said: “High quality oak casks are crucial in the maturation of quality Scotch whisky, with the interaction of the spirit and the cask as the whisky matures having a vital influence on the final whisky.
“The focus of the work with Napier University was new research into the maturation process designed to optimise the use of the traditional oak casks we use to mature our Scotch whiskies.”
Intriguing but I would have thought that if you half the Angels’ share, you would double the required maturation time?
Most types of oak are chosen for the level of absorption they offer and are used by different cellar masters to suit their own distillation requirements. In order for the reaction between the oak and spirit to occur, it is necessary for the spirit to penetrate the oak for as long as possible. The only way one can reduce the spirit evaporation is for the barrels to be in damp conditions. A water molecule is bigger than a spirit molecule so a damp outer will tend to block the eventual evaporation of the spirit. It is difficult to understand how any change in the physical structure of the barrel can benefit the barrels contents.
I’m sorry, David, but your comment contains some serious inaccuracies. First, a water molecule is not “bigger” than an alcohol molecule, no mater how you look at it. Water, H2O has a weight of 18 grams/mol while Ethanol, C2H6O, has a weight of approximately 46 grams/mol.
The concept I believe you’re trying to articulate is one of temperature and relative vapor pressure rather than molecular weight. Alcohol has a lower boiling point than water. At any given temperature, all other things being equal, alcohol will always be more likely than water to evaporate. At a lower temperatures, both will evaporate at a lower rate.
You are correct that relative humidity in the rickhouse is what reduces the evaporation of water relative to alcohol, but there is no “blocking” involved. For the same reason that a glass of water will evaporate faster on a very dry day vs. a muggy day, the vapor pressure of the liquid is inversely proportional to the content of its vapor form in the surrounding atmosphere.
As for why a change in barrel structure can benefit the contents, the “tightening” of staves has the net effect of reducing evaporation. While a standard barrel may be watertight, the minute spaces between staves are anything but airtight. A barrel that is coopered so as to minimize that space even further will result in a reduction in angel’s share. Another way that barrel structure may affect the final product dramatically is size. Smaller barrels (often referred to as quarter casks and “kilderkins”, have significantly greater surface area, and have been used widely in recent years to impart more flavor and “age” whisky more rapidly.
Very interesting subject of finding.It is of very vital importance for the industry.If proved beyond doubt & without compromising the sensory quality, it will revolutionize the concept & would mean a big saving in revenues & carbon footprint.
Diageo have full whisky casks in the warehouses at Blackgrange Bond wrapped up in plastic film using a hay bail wrapping machine to see if it reduces the angels share. The funny thing is the slit the wrap to let the whisky breath… Does that not totally defete the purpose?
I have a question directed as someone who really understands the physics of the Angel’s Share. Specifically, do you know how much of the evaporation is lost through the wood, from the cracks in between the staves and from the cracks in between the staves at the top of the barrel. What I am looking for is an idea of how much is lost because the staves at the top of the barrel when it is resting in storage will naturally dry out more than the staves at the bottom of the barrel where the whisk(e)y is still in contact with the inside of the stave. I hope this makes sense. I’m an old navy guy and aside from loving whisky, I know that when a wooden boat is taken out of the water, openings form between the boards which is what leads to leaks. just wondering if this is relevant to the storage of spirits. I’m sure some distilleries rotate the barrels but I know some do not. Anybody have a good answer?