by db1979 » Tue Dec 19, 2017 11:07 am
I reckon this is a matter of the equilibrium system in the spirit. It's a series of dynamic (constantly changing) reactions that occur where the reactants are reacting to make products and at the same time the products are reacting to go back to the reactants again.
Over time, if left undisturbed, an equilibrium system will establish at a specific point where the amount of reactant and product appears to be fixed and unchanging (this is referred to as "at equilibrium"). In reality, the concentrations of both are staying the same because the reaction that uses up the reactants is happening at the same speed as the reaction that uses up the product.
The concentration of the reactants and products will influence the position of the equilibrium (favouring more reactants or more products) and so adding water to the spirit will cause the dynamic system to respond until it reaches equilibrium again (this is because water is a reactant in the hydrolysis of esters). This means the speed of the two reactions will change until they both become equal again. This takes time, especially for slow organic reactions, like the hydrolysis of large esters by water into fatty acids (soap taste) and an alcohol.
Adding water slowly may help to keep the equilibrium from going too far from where it was in the barrel (and possibly needing more time to readjust) and then needing less time to return closer to where it was before the addition of water.
On the other hand, quick dilution with water should just need time for the spirit to sit and return to equilibrium. Perhaps it's faster overall to add the water slowly.