Introduction This is a new series of iStill Blog posts, where a distiller asks a question and Odin answers. In his well known style. Direct and to the point. Always straightforward, sometimes confrontational. Read it, digest it, don't feel offended. The way it works? If you have a question where you think the answer can benefit you as well as the rest of the industry, give it a go. Email your question to Sales@iStillmail.com and Odin may chime in. Please know that the questioner will always stay incognito. Please also know that Odin will select if and when and what question he feels like answering. So if you don't see your question back here, on the iStill Blog, don't feel offended. Question Hi Odin, I'm a huge fan of your posts and content - thanks for being such an active contributor! I was chatting w/ another distiller at our place recently and he seemed appalled that we were just dumping RO water into our spirits to proof them down based on a target proof and volume. How he was taught, was that spirits need to be proofed down very gradually over time (sometimes even years?!?!?!) to minimize any sudden changes the spirit would go through that could negatively affect the final spirit. We rest our gins for at least a month in steel prior to bottling, as you've told many to do, but it sounds like they proof their gins and whiskies down to bottling proof gradually over many months. Have you heard something similar and do you find any truth to this statement? Aside from reserving half a batch of gin and performing this trial ourselves, I wanted to reach out to see if you could shed some more light on this. It seems to me, that whether the water is added in quickly, or slowly, there is nothing else "forcing" chemical reactions to happen more quickly or slowly.... as long as you give the spirit a week to stabilize, it seems like it shouldn't matter.... Thanks for your time! Answer Hi, Thanks for reaching out. Glad to see you like my posts. If you encounter any and give them a thumbs up that would be appreciated! Theoretically, if you proof down in one big gulp, this can happen: temporary (for a few seconds up to a minute) certain parts of the now diluted gin or whiskey may see a situation of uneven water/alcohol distribution. You aim for 90 proof, poor in water, and parts are 100 proof and other parts are 80 proof. Makes sense? Now, the 80 proof parts can (temporarily and theoretically) put the oils in 'm (especially tails oriented tastes - so pot distilled whiskey or heavy rum) out of solution, and if they come out of solution, this gives them a change to (relatively) overly evaporate. Reason? Solvency power (for taste oils) is lower at lower proof. Now, that's the theory. Practically, this does not happen, especially if you stir or if you add the dilution water with force. If you add it slowly without causing any agitation, its the top part of your mixing tank that you dilute. And it is at the top that evaporation takes place. So here it comes (and hence the misunderstanding): an example where things can go wrong in practice. Say people treat their whiskey gentle and dilute slowly. Now they take a reading and it does not make sense (because of the uneven distribution). The distiller's mindset? "Something is going on! The math was right, right? I have to be more careful!" They wait. Guess what, another reading a day later and its spot on (because of now even distribution). Instead of being more careful, add the dilution water hard and fast, and aim for 91 proof. The smaller the amounts and the gentler the pours, the lesser the agitation and mixing that takes place and the more relative potential evaporation of tails oriented flavors actually happens. Why? Because any evaporation takes place at the top of your mixing tank. Or better put: if you dilute slowly at the top. So dumping in the biggest part is the way to go. Fast and hard, so the dilution water reaches deeper down. Then give it a 5 minute stir (manually will do), then measure again. Then go the final 1 proof down (or so) to reach your goal ABV. Hope this helps, Odin. PS: The weird thing is most whiskey and Bourbon in NA is now made on what was traditionally a fruit brandy still: plates with bubble caps. Great at preventing tails smearing ... so the whole evaporation is a real non-issue due to lack of fatty acids coming out of solution for most distillers. It is only an issue if one dilutes a pot distilled product slowly and without agitation. A pot distilled product that aims to reap the benefits of tails oriented flavors like heavy rum and single malt whisky.