Reducing the proof of whiskey to bottle proof is an interesting subject. People talk about filtration, but not many people talk about the water added to adjust the proof. Most big distilleries simply dump the whiskey from the barrels into a huge tank sitting on scales. They weigh the whiskey, check the proof and then using mathematics, figure out how much water is needed to add to reach the desired proof, and then they add Reverse Osmosis treated water. This is the most efficient way to reduce proof and it works fine with the chill filtration systems of today. However, that is not the way it has always been done.
In Europe, the ancient way of reducing the proof of brandy was to add water to aging barrels every year to reduce the proof as it aged. There is always a little angel’s share in the barrel and so topping it off the barrel with water to reduce the proof of the spirit and give the spirit time to incorporate the water into the spirit was how they reduced the proof. When the desired proof was reached, they would stop adding water. This works fine for a small distillery with only dozens of barrels produced per year, but on a larger industrial scale, something else needed to be done.
On a large scale, brandy producers of today dump their barrels into a tank and then add water to reduce the proof only about 3% at a time, waiting a week between additions of water. It may take several weeks to reduce the proof to bottling proof, but it does allow the water to incorporate into the brandy more efficiently.
I discussed this with Alan Bishop at The Spirits of French Lick Distillery. Alan has experience as a brandy distiller as well as a whiskey distiller. He tells me that this is important when making a whiskey or a brandy in a pot still. There are more of the grain oils coming through with pot still distillation of whiskey and too much water at one time causes chemical reactions that create globules of oil that can cause an off-taste in the spirit. He reduces his whiskey by adding water over a period of time and aerates it as well to prevent this from happening so he does not have to chill filter the spirit before bottling.
Alan explained that with column still distilled spirit, fewer oils from the grain pass through the distillation process, and with modern chill filtering processes adding the water at one time is less a problem for the distiller. He states that he has found many pot still whiskeys that he has enjoyed when he first tried it, but then found that they were not so good the next time. He believes that this was caused by the proofing down for bottling. Alan believes the secret is to make sure the temperature of the water and the spirit are very close when proofing down. A large difference in temperature can cause problems.
There is more to reducing the proof of whiskey to bottling proof than just adding water. Lincoln Henderson stated that a distiller has to get it right every step of the way to bottle a good whiskey. Willy Pratt was a firm believer in creating a filtration system that fits the whiskey to be bottled and the proofing down was probably a huge part in doing his evaluation of the whiskey to pick his method of filtration. It is something every artisan distiller should consider before bottling their whiskey. It would be a shame to do everything well up to that point and then mess it up in the end.
Photos Courtesy of Rosemary Miller
July 31, 2021 at 7:00 pm
The increase in temp as a result of addition of water to the matured whisky should be taken care by relatively chilling the water to the extent that takes care of the increase in temp as a result of exothermic reaction. So that both the Spirit & water strike temp are same everytime on the dilution. Will this be the right approach.
August 8, 2021 at 4:26 pm
Maybe. I am not sure of the chemistry here, but contact Alan Bishop at the Spirits of French Lick Distillery. He can discuss it with you in detail.
January 16, 2023 at 5:52 pm
Adding water to high-proof alcohol is an exothermic reaction, I.e., it’ll produce some heat and elevated temperature.