Sorry, I want to set my question up a bit, so bear with me.
I've brewed 4 batches, all partial mashes. The last batch I brewed, I took a hydrometer reading immediately after lautering to get an initial boil gravity of 1.045 for 5 gal. of wort (I stirred the wort thoroughly to make sure the first and second runnings were well mixed). During the boil, I added 1 lb. of candi sugar syrup at 32 ppg and 2.5 lb. of LME, which I assumed was at 36 ppg. By my calculations, that should all add up to 347 total gravity points, which, for a 5.25 gal. batch, should have given me an OG of 1.066.
However, after adding a 2 qt. yeast starter (OG 1.040) and 1.25 gal. of top-off water to the final 3.5 gal. of wort I got after the boil, and shaking the fermenter really vigorously for several minutes (producing several inches of froth on top), I measured an OG of 1.059.
Something similar happened in my previous two batches as well, where, based on measured initial BGs and the amounts of extract added, I expected OGs of 1.047 and 1.060 but measured OGs of 1.044 and 1.053, respectively.
I thought I understood how to calculate gravities based on gravity points, but am I missing something? Why would adding top-off water have such a great effect on my gravities, so they are several points off what I expected based on my calculations?
I read in some threads on the forum that it is hard to get an accurate gravity reading after adding top-off water because of the difficulty of mixing wort and water, but again, for each of these batches, I shook the fermenter (very) vigorously for several minutes after adding top-off water before taking a hydrometer reading, so that there were several inches of froth on top each time. Is it so hard to mix wort and water that you can't get an accurate hydrometer reading even after this much shaking of the fermenter?
The only other thing I can think of is that the extract I am using has a much lower yield than I am assuming (it would have to be between 21 and 29 ppg to get the readings I got), but this doesn't seem feasible. Is there another explanation for my low gravity readings?
Thanks for any help you can give.
I've brewed 4 batches, all partial mashes. The last batch I brewed, I took a hydrometer reading immediately after lautering to get an initial boil gravity of 1.045 for 5 gal. of wort (I stirred the wort thoroughly to make sure the first and second runnings were well mixed). During the boil, I added 1 lb. of candi sugar syrup at 32 ppg and 2.5 lb. of LME, which I assumed was at 36 ppg. By my calculations, that should all add up to 347 total gravity points, which, for a 5.25 gal. batch, should have given me an OG of 1.066.
However, after adding a 2 qt. yeast starter (OG 1.040) and 1.25 gal. of top-off water to the final 3.5 gal. of wort I got after the boil, and shaking the fermenter really vigorously for several minutes (producing several inches of froth on top), I measured an OG of 1.059.
Something similar happened in my previous two batches as well, where, based on measured initial BGs and the amounts of extract added, I expected OGs of 1.047 and 1.060 but measured OGs of 1.044 and 1.053, respectively.
I thought I understood how to calculate gravities based on gravity points, but am I missing something? Why would adding top-off water have such a great effect on my gravities, so they are several points off what I expected based on my calculations?
I read in some threads on the forum that it is hard to get an accurate gravity reading after adding top-off water because of the difficulty of mixing wort and water, but again, for each of these batches, I shook the fermenter (very) vigorously for several minutes after adding top-off water before taking a hydrometer reading, so that there were several inches of froth on top each time. Is it so hard to mix wort and water that you can't get an accurate hydrometer reading even after this much shaking of the fermenter?
The only other thing I can think of is that the extract I am using has a much lower yield than I am assuming (it would have to be between 21 and 29 ppg to get the readings I got), but this doesn't seem feasible. Is there another explanation for my low gravity readings?
Thanks for any help you can give.
