Last time, I mentioned that I had two stages left in my process. The next to last stage was bourbon barreling the beer. I didn’t have a bourbon barrel. I did have bourbon, and I did have oak chips. That was enough for me. I took some of the oak chips and decided to let them soak in some of the bourbon. While that was happening, I did some calculations to figure out what sort of effect I would get by adding bourbon. Through a ratio field test (the lay way of saying that I made some extreme boilermakers to see how the bourbon would come through), I settled on an appropriate level of bourbon.
My beer gravity was 1.092, meaning the the beer was 20.37 (and some)% ABV after the difference from the initial gravity. The bourbon I had was hot. It was 65.05% ABV. So, I took the amount of 20.37 and multiplied it by 84 ounces of beer. Then I took 65.05 bourbon and multiplied it by my ounces of bourbon (14 ounces, in this case). I added the two products of the multiplication and divided by the total ounces. It looked a bit like this:
65.05% ABV*14 ounces=910.7
So, my ABV from the Bourbon addition yielded 26.76% (roughly) ABV. I approached this two ways to make sure that I was getting an accurate reading. First, the simple math from the hydrometer told me my ABV. From there, it was only a matter of figuring volumes. The other check had to do with the relative density in solution. So, the effect of the alcohol was to drop my hydrometer to give me a new reading of 1.075. I figured that for every percent alcohol on the hydrometer reading, I was actually getting 2.8143295% by volume increase.
I know this is getting a little convoluted, but the relative density of a distilled spirit is actually less than water and it affects the gravity reading in the negative even though the ABV goes up. I’m not going to go into the math because it’s tedious, and it took a long time to figure out.
The only reason I bothered was for the next stage in my beer: I still had to eisbock the brew, which involved the removal of water. Fortunately, the decreases viscosity of the beer via the addition of distilled spirit renders the beer more freezable. However, the gravity was still pretty high and reminded me once again that my initial gravity was simply too high. Next time, I’ll get it right.
Since I’m removing water, the thickness has re-increased. All this means is that my gravity is going to go back up. Therefore, I’m still using the formula that says for every 1% of ABV on the hydrometer (still basing the idea on relative density from the Bourbon), I’m actually getting 2.8143295% ABV. Sorry if this has become too much. Let me put it this way: The more moisture loss I see, the more water I know has been removed from solution, thus the more ABV. Yet, because of the effect the bourbon had on the beer, I can’t rely on simply getting a straight reading, hence all the calculating.
I promise that the next section will be more interesting. Let me just say that I had an almost 27% beer that I put in the freezer and wish it would have been less thick. The bourbon did thin it a bit, which meant for a little better freezing. We’ll see. Even as I write this I’m still not done eisbocking. Stay tuned, I only have one more post and will reveal how the thing ended up.