||11-25-2012 11:42 PM
Mystery low FG
So, I'm a relative beginner, I've brewed maybe a dozen all-grain batches. Starting to get the hang of it. I recently purchased a refractometer to make gravity readings easier. Prior to that purchase, I had never measured the final gravity of my beer, mostly because of contamination concerns and because using a hydrometer wastes a lot of beer (relative to a 5 gallon batch).
Anyway, for the last 2 batches I've been able to measure the final gravity as I'm racking it to the secondary. And, both times it has been surprisingly high, in the 1.030 range. However, in neither case did the beer taste sweet, as one might expect in an incomplete/stuck fermentation. In fact, in both cases, the beer tasted quite good, close to what I was shooting for.
Both brews were all-grain batches. One was mashed around 150 degrees, the other around 148. I did an iodine test at the end of the mash on both batches to ensure that all starches were converted. I saw normal and vigorous yeast activity in the primary on both batches.
I can't understand why the final gravity is so high, 7+ days into the fermentation, well after yeast activity has plummeted. The beer tastes fine, but I wonder if something is wrong with it? Or maybe I'm just using the refractometer incorrectly? It seems to be calibrated correctly, since if I put water on it, it reads 1.000 exactly. And, when I'm testing the pre-boil gravity and original gravity during the brew, it seems to read reasonable/expected values.
Any ideas of what else I can check?