I recently brewed the St. Paul Porter kit from Northern Brewer, and got a consistent final gravity reading over the past couple of days. However, the numbers seem a bit off.
I got an OG reading of 1.048 and a FG reading of 1.021. From what I can tell, that's about 3.5% ABV. The beer should've finished off around 5.5% or so, based on others' comments. Any thoughts on why this happened?
I fermented around 70-72 degrees. Visible fermentation in the airlock for a couple of days, but nothing crazy. I did not use a yeast starter for this brew.
Should I consider pitching some more yeast on it and going for a second round? Am I doing the math wrong?
Thanks for the help!