A question for you mashing experts out there...why does efficiency drop so drastically when mashing a high gravity beer, but a similar amount of malt & water for a 'double size' batch results in normal efficiency...why?
Brewed an Imperial Stout on my Brewzilla 65L Gen 4 yesterday, using a full 21lb of malt & 1.5lb sugar and shooting for a 1.107 OG and 5.25gal batch size. That OG was using an assumption of 70% efficiency, which is 7-8 points lower than normal. What I got was shocking...about 60% efficiency with a 1.090 OG. While efficiency losses are common with high gravity beers, what occurred to me was that this batch in some ways was not that different than a 10gal one. A 10gal lager batch would use almost the same amount of malt, uses a similar amount of water, but boils for less time than the 90-min boil I used on the Imp Stout. But, the 10gal batch efficiency will be in the high 70s, much higher than the Imperial Stout that I just did.
One of the explanations for the high gravity efficiency losses is the thick grist to water ratio. While the Imp Stout grist was more thick than a 10gal lager batch, it was not vastly different. And, I question whether that is the only reason for the massive efficiency differences. The Stout boiled for a lot longer to get down to a 5.5gal volume, but that would not effect efficiency. The clear difference is in the volume and gravity of the resulting beers, but how does that effect efficiency when mashing?
Brewed an Imperial Stout on my Brewzilla 65L Gen 4 yesterday, using a full 21lb of malt & 1.5lb sugar and shooting for a 1.107 OG and 5.25gal batch size. That OG was using an assumption of 70% efficiency, which is 7-8 points lower than normal. What I got was shocking...about 60% efficiency with a 1.090 OG. While efficiency losses are common with high gravity beers, what occurred to me was that this batch in some ways was not that different than a 10gal one. A 10gal lager batch would use almost the same amount of malt, uses a similar amount of water, but boils for less time than the 90-min boil I used on the Imp Stout. But, the 10gal batch efficiency will be in the high 70s, much higher than the Imperial Stout that I just did.
One of the explanations for the high gravity efficiency losses is the thick grist to water ratio. While the Imp Stout grist was more thick than a 10gal lager batch, it was not vastly different. And, I question whether that is the only reason for the massive efficiency differences. The Stout boiled for a lot longer to get down to a 5.5gal volume, but that would not effect efficiency. The clear difference is in the volume and gravity of the resulting beers, but how does that effect efficiency when mashing?