I get how to calculate attenuation, but I'm not really sure I understand it. If I have a wort that I want to dry out past intial FG, can I just keep pitching fresh yeast to get multiple fermenations of say 73% (wyeast website mean attenuation = 73% for Irsh ale yeast) attenuation rate? This intuitively doesn't seem right, but I don't know.
My problem: I brewed a stout two weeks ago, with OG of 1.084. Made a nice starter and fermentation started pretty quickly and actively. After three active days fermenting in my 60F basement (temp strips read 67), I moved fermentor into a warm chamber at about 65 and went on vacation. While away, the breaker on my heater cicrcuit tripped and ferm dropped to 58% for a few days. When I got home I read gravity (1.025), fixed the heater problem, warmed the beer up to 68F, roused the yeast and let it go for another 6 days. Had no sign of activity and gravity remained the same at end of those 6 days; I think that I had uneven temps in my mash with some very warm spots. I'd like to get this beer more in the 1.018 - 1.020 range. If I pitch a yeast with higher attenuation (SafeAle US05, for example, for wich Fermentis indicates 81% attenuation) on top of the Irish ale, could I expect to see an 81% attenuation of the current gravity (.025), or an overall attenuation 81% of my OG of .084?
My problem: I brewed a stout two weeks ago, with OG of 1.084. Made a nice starter and fermentation started pretty quickly and actively. After three active days fermenting in my 60F basement (temp strips read 67), I moved fermentor into a warm chamber at about 65 and went on vacation. While away, the breaker on my heater cicrcuit tripped and ferm dropped to 58% for a few days. When I got home I read gravity (1.025), fixed the heater problem, warmed the beer up to 68F, roused the yeast and let it go for another 6 days. Had no sign of activity and gravity remained the same at end of those 6 days; I think that I had uneven temps in my mash with some very warm spots. I'd like to get this beer more in the 1.018 - 1.020 range. If I pitch a yeast with higher attenuation (SafeAle US05, for example, for wich Fermentis indicates 81% attenuation) on top of the Irish ale, could I expect to see an 81% attenuation of the current gravity (.025), or an overall attenuation 81% of my OG of .084?