Consistently High FG (All Grain)

[guinnessface]

Brewers-

I'm a little stumped here, I'll defer to the experts on this. My last three AG batches have finished with uncharacteristically high FG. I'm pretty experienced and haven't run into this problem before. All 3 were in the 1.05 to 1.06 OG range and finished around 1.04-1.06. Here's what the conditions were (All were mashed around 154-156 degrees):

Beer 1: Coffee Porter. This had lactose, so I expected the high FG, but there were still more to ferment out at the end.
Beer 2: Double IPA. This finished around 9%, but I used honey for a cleaner finish, it's still pretty cloying. For this and the porter, I used Cal Ale yeast and fermented around 68-72 degrees.
Beer 3: Hefeweizen: I used a Hefe Ale yeast and same fermentation conditions...it only went from a 1.054 to a 1.014 after 3 weeks and re-agitation...it initially had a very active start. Plus the finished product is more tart than I expected. In the past, the FG on this recipe usually ends up right around 1.01.

So with the 1st 2, I used starters and let things go for about 3 -4 weeks in a conical. I'm pretty sure I even re=pitched some more yeast in the porter, so it leads me to believe it's a mash problem rather than a fermentation problem.

I hit my strike temps in a cooler, spot on, then leave it for about an hour. Will the dropping temp cause a rise in unfermentable sugars? It hasn't been a problem in the past. I usually heat the sparge water up to 180 and even that only brings the mash up to the upper 150's....maybe the conversion is going on too long? I wonder if a mash out after 45 minutes would help instead.

I've double checked other things like m thermometer and equipment; everything is calibrated properly. The only remaining thoughts I have is that maybe the temperature change is affecting the beer (at the top of a finished basement stairwell, next to the kitchen). Maybe the swings in temp from the oven and cold from the basement have an effect, though they haven't in the past!

I'm at a loss here. I've tried to look at this from several angles and keep coming up short. Any thoughts you might have would be greatly appreciated.

All the best, and cheers!

guinnessface

 

[fosaisu]

What was your FG for the first two beers? It reads like they finished at 1.040+, which seems extremely high, especially if starting gravity was 1.050 or 1.060. I'm guessing they actually finished at 1.014 - 1.016? If so, that's within the range of acceptable FGs for many yeast types, and especially so for a DIPA. That said your mash-temp theory makes sense, and you might be able to bring those FGs down a bit by mashing a few degrees cooler (I don't think sparge temp should have much impact on wort fermentability).

 

[flars]

Have you changed from using a hydrometer to a refractometer for FG?

 

[Beernik]

154 - 156F is high to be mashing at and if your thermometer is off by a couple degrees, you could up up to or over 158F. At 158F, you're getting mainly dextrins instead of sugars.

I'd first check your thermometer calibration and second mash your next brew around 150F. The only reason to mash over 150F is if you want a less fermentable wort.

 

[guinnessface]

Thanks all. To clarify, I mistyped: it was 1.014, not 1.04. I use a pretty reputable scientific thermometer that's cumbersome, but reliable. I tried a digital one for a bit, but wasn't crazy about the results....I haven't tried a refractometer yet. I may try to lower the temp for the next batch, but am still puzzled as to why my "repeatable" recipes are turning up with high FG. Great insight though, I appreciate the help

 

[Gnomebrewer]

Brewers-

I hit my strike temps in a cooler, spot on, then leave it for about an hour. Will the dropping temp cause a rise in unfermentable sugars? It hasn't been a problem in the past. I usually heat the sparge water up to 180 and even that only brings the mash up to the upper 150's....maybe the conversion is going on too long? I wonder if a mash out after 45 minutes would help instead.
guinnessface

The dropping mash temperature will do the opposite - it will give you more fermentable sugars. The longer conversion will also do the opposite - it allows Beta-amylase (which is slower to act than Alpha-amylase) more time to convert starch to fermentable sugar.

Have you recently started measuring the temperature in a different part of the mash tun? There can be considerable variation throughout the grain bed, and for consistency you need to always measure temperature in the same place. Just a thought.

The final gravities sound about right for the mash temp you have been using (which is quite high) but doesn't explain why your FG's have changed recently using the same process. Whatever the reason is, lowering your mash temp by a few to several degrees should help.

 

[guinnessface]

Perfect, thanks. Excellent advice

 

[Natdavis777]

The FGs dont seem out of character, but like stated, I would lower the mash temp, especially for any type of pale beer.

One issue that popped in my head first, that was brought up, was thermometer accuracy. Maybe test it @ freezing and boiling temps to insure that its accurate. A few degrees here and there during the mash can affect FG by a few degrees.

 

[guinnessface]

@Natdavis: Will do, thanks