LLBeanJ
Well-Known Member
As others have stated, mash temp directly affects the fermentability of the wort and, therefore, FG. Lower mash temps will result in lower FG and vice versa.
I think your issue is a result of a couple of things:
1) Partial mash. It's not uncommon for extract to result in a higher FG than expected. Since you brewed this as a partial mash with a high percentage of extract, I would speculate that the extract is mostly responsible for the high FG. Next time, try replacing some of the extract with table or corn sugar to help lower the FG;
2) Mash temp too high. Granted, the partial mash results in a much lower grain bill than you'd have if it were an all-grain batch, so the mash temp will have less of an affect on the FG than it would if it were all-grain, but it will have some affect nonetheless. Also, unless you added some pale malt to the mash, the Munich is the only base malt you have there. Munich is not very high in diastatic power, but it is high enough to self-convert and convert other grains as well; it may just take longer than 60 minutes. Fortunately, the higher mash temp would have aided in the conversion process. Regardless, I would think that whatever sugars you did get from the mash were probably less fermentable than they would have been if you better controlled the mash temp and held it to around 150° for, say, 90 minutes. The lower temp would produce a more fermentable wort and the longer mash would ensure full conversion of the starches.
