nathanm wrote:Forgot I posted this - thanks all for the detailed responses, they don't go unnoticed. I have tried to wrap my head around the idea of adding sugar (and thus gravity) for the purpose of achieving a lower gravity. Seriously this doesn't make sense to me no matter how much I think about it. Does it just get the yeast going again and they eat all the added sugar and while they are at it, eat some more the maltose etc?
Thanks again.
The thing is, you aren't adding sugar to achieve a lower FG. You're replacing some base malt with sugar to achieve a lower FG. Let's say you brew a 5% ABV, 1.050 OG IPA at 75% apparent degree of fermentation (FG is 1.012) and add to that 10 gravity points of sucrose. Now you have a 6.6% ABV, 1.060 OG IPA at 83% ADF (FG is 1.010). Everything else being equal, if you had just brewed an all malt 1.060 IPA with a yeast capable of 75% AA, you'd have a 6% ABV beer with a 1.015 FG.
Here's the same thing, but in a table. The bolding illustrates how the next recipe is connected to the previous.
Small IPA....................IPA w/sucrose....................All malt IPA
OG: 1.050........................1.060...............................1.060
FG: 1.012..........................1.010................................1.015
%ADF: 75%......................83%..................................75%
%RDF: 63%.....................69%.................................63%
RE: 1.019........................1.019................................1.023
%ABV: 5%........................6.6%.................................6%
(The residual extract, RE, is held the same between #1 and #2 because the both contain the same amount of sugars in the end. I.e., all of the sucrose is fermented completely.)
(The real degree of fermentation, %RDF, is held constant between #1 and #3 because the same yeast, given the same wort composition will ferment the same absolute percentage of sugars. In reality this probably wouldn't work for, say, a 1.060 IPA and 1.110 barleywine because of the additional stress upon the yeast.)
I probably over complicated that, but I like thoroughness. Hope it helps.
