Ibiduin said:
I've currently started a batch, extremely sweet (1.17), and am planning on adding water down the road and re airating close to the end of "first" fermentation.
He sounds to be very early into fermentation (less than 2 weeks?) Nutrients would be a good idea if he hasn't added any... they will help the yeast convert more of the sugars, but I doubt the yeasts are even close to being stressed this early(except for the stress of a high gravity).
Without nutrients he would be in for a very long fermentation. If he had added nutrients and the heat was in the high 70s to 80s then the yeast might have brought the ABV high enough and the nutrients low enough to stress the yeast. In any case... in my mind the only thing diluting would do at this point is lower the stress on the yeast by lowering the gravity and Alcohol %. IMHO it would be best to add the water while the batch is still very young. A definite no on late aeration though.
Excerpt from a paper on High gravity brewing - This environment (high gravity) can leave even the most resilient yeast more susceptible to infection, mutation, and damage. Inhibiting growth factors, yeast stress and subsequent fermentation problems.
Taking the above into account... it is my belief that the easiest way to relieve stress in a high gravity environment is to dilute as soon as possible, taking efforts to minimize aeration. Doing so will return the environment to a more acceptable range for the yeast, they in turn will be healthier & happier for the remaining duration of the fermentation.
In response to - When diluting the must, sugar is not the only nutrient to consider. Nitrogen sources, vitamins and other growth factors can become limiting. - True... to a point, but not noticeably more than if the mead had originally been started at a lower gravity (if it's still early into the primary fermentation)
I do believe fermaid K would be an excellent addition if diluting at this point though.
Wrathwilde