gravity issue

So the musts og was 1.18 ending after the primary with an acceptable 1.06 (going for a sweeter mead). After racking on some oak chips and adding a gallon of water (i lost a bit from the yeast cake and fruit cap) the SG was at 1.05

So my question is do I take this as a negative gain in terms of abv? Ie: 1.18 to 1.06 yields approximately 16% and with the change from 1.06 to 1.05 would that mean my final abv is 15% +/- .4%?

Could use some help.

Hard to really know with the addition of a gallon of water. More math involved than I care to undertake. Was 15.5 before the water addition.

120 point drop equates to 16.3% ABV - you don't say what your ingredients were (yeast specifically), so no idea of whether there's any room for increasing that with any modified technique.

So unless you want to be really anal about the % ABV, I suspect you're about right with the guesstimate of 15 to 15.5 %.

Irrespective of that, with a finished gravity of 1.060 (see, 3 decimal points, as is the norm when quoting gravity figures) is gonna be sweet as hell, to my taste, that'd be "cloyingly" sweet.

You could mask that a bit, by balancing it with some acid (I use the mix suggested in Ashton & Duncan's book "Making Mead" (out of print now) which is 2 parts malic acid to 1 part tartaric acid), but whatever you use, I'd take a little must, mix it with some acid (a teaspoon at a time - I'm guessing this is a 5 gallon sized batch) and then add it in, stir gently to mix and taste.

You need to tell us how big your batch was...

You can average the ABV in each volume. How much mead did you rack to secondary?

If you needed to add a gallon of water, I'll guess you racked 4 gallons into a 5 gallon carboy. Here's how I would calculate it.

4 gallons mead @ 16% ABV
1 gallon water @ 0% ABV

(4 x 16) + (1 x 0) = 5 gallons at "X" ABV
64 + 0 = 5X
64 =5X
64 / 5 = 12.8% ABV

You could also do it this way. If you racked 4 gallons of 16% mead, it contained 0.64 gallons of alcohol. 4 x 0.16 = 0.64 gallons alcohol

If you added a gallon of water, then you now have a 5 gallon batch containing 0.64 gallons of alcohol. Divide the alcohol by batch size. 0.64 / 5 = 0.128 or 12.8% ABV

Thank you guys you helped a lot. Yes it was a 5 gallon batch and yes I racked 4 gallons into the secondary. I also used lalvin 1118.

Thanks again for the help on the math I simply didn't know where to start with it.