I mentioned this problem in the Brewing Activities thread and it has come true: I brewed a Maine Beer Zoe clone and did a 2.5-gallon batch. I misread my boil-off rate in my notebook (doh!) and ended up with an OG of 1092 instead of the target 1074. I used a dilution calculator and got it down to 1076, and I was fairly happy with this. I then pitched, per the recipe, 3/4 of a packet of US-05. However, I just took the first reading today (it's been in the fermenter for 12 days) and it was 1010. 8.6 ABV(!) compared to the target 7.2%. This is a problem I've been having lately: The OG is usually a tad low, which makes me weep over a grain bill calculator and my low efficiency. But then the FG comes in way below what it's supposed to be. I don't know if my hydrometer is off - I measured a long time ago in water and it seemed right on. The really frustrating part is that even diluted it's only going to give me about 22 - 24 12-ounce bottles, but 12-ounce bottles of what is now an imperial amber. I would rather have 30 bottles of 7.2 percent hoppy amber. Estimates were: Recipe OG 1064 FG 1009 According to Brewer's Friend grain bill calculator with the grain I used OG 1074 FG 1021 What I got OG 1076 FG (so far) 1010 What am I not seeing here? Thanks in advance.
When a tool gives an estimated FG that is based upon an assumed attenuation. A tool really doesn't 'know' how fermentable a given wort is (i.e., percentages of the various sugars in the wort). Can you please provide a list of grains you used in producing your Zoe clone and the specifics of your mashing regime. It seems that you produced a wort which was highly fermentable (i.e., had a lot of simple sugars which are very fermentable) and the result is the low FG value. Cheers! P.S. For further reading: https://byo.com/article/whats-in-your-wort/
Hey, Jack. Thanks for the reply. I used: 3.3 pounds Weyerman pale 3.3 pounds Maris Otter .45 pounds Munich .45 pounds amber .2 pounds crystal light .2 pounds crystal medium .12 pounds chocolate malt I milled twice using the smallest setting and mashed for 80 mins (recipe called for 60) at 151º degrees. I mash in the kettle, so controlling the temperature is a little tough. I had to reheat the wort, so I let it go a bit longer. I also mash longer due to efficiency problems in the past. I mashed with 2.7 gallons and sparged with .7. (I brew in metric, hence the whacky measurements).
With that grain bill and mash temp/length, an OG of 1.076, and US-05, I'd expect an FG of about 1.015. How certain are you about the volume of wort you had before adding water to dilute? Did you measure it, and if so, was it still hot when you did? (Volume will be (temporarily) higher at higher temps.) ETA: I also note that the attenuation you seem to have got is almost the same as the attenuation the recipe called for.
Thanks for the reply, VikeMan. The OGs are really coming to the aid of the rookie today! The level is marked on the fermenter. It was 2.24 gallons when I put it in, and it is sitting just a hair over 2 gallons now. Can I ask what software/tool you used to calculate this?
I'm not sure I follow. What was the volume and temperature of the wort before you added water and how did you measure it? And how much water did you add?
Sorry, I misread your question. I measured the gravity and it came in at 1092. I used a dilution calculator, which said to add .36 gallons to get to 1076. I had chilled the wort when I took the sample and it was at about 75º F. I put the original quantity into the fermenter, then boiled more water and added it.
What was the volume of the 75F wort before you added the water, and how did you measure the volume of the wort? And how did you measure the volume of the water? What I'm getting at here is gravity dilution needs pretty accurate measurements of the wort and the water. If either is off, you won't hit the expected combined OG. If the combined OG was actually lower than 1.076, that could explain (at least partially) a lower than expected FG.
Just to double check, the value you quote above of 1.076 is from he calculator? Or did you actually measure the specific gravity after adding the water? And if you did conduct a measurement did you do anything to ensure proper mixing (e.g., did you stir the wort after adding the water)? Cheers!
Sorry for leaving that out. The pre-diluted volume was 1.85 gallons, as measured by the fermenter. If I understand your second question, I measured the water that I boiled in a Pyrex measuring cup.
If my Apparent Attenuation numbers were consistently higher (or lower) than expected, I'd be (first) looking at my mash temperature, i.e. making sure my thermometer was calibrated. I say Apparent Attenuation rather than FG, because you'd expect FG to be low when OG was also low. The question is whether or not the attenuation (percentage) is as expected.
Well, with an OG of 1.076 and a specific gravity reading now of 1.010 you have achieved an Apparent Attenuation of 86%. As a basis of comparison for my last batch of IPA I had an OG of 1.062 and a FG of 1.009, an Apparent Attenuation of 85%. So you are pretty much in line with me here. Cheers!
If you would prefer to achieve lower attenuation there are some options: Mashing To achieve a wort with more unfermentables: Mash at a higher temperature (e.g., 154 - 155 degrees F) Mash for less time (e.g., 45/60 minutes) Or you could do both of the above. Grain bill Use more specialty malts like crystal/caramel malts since they will add more dextrins to the resulting wort. Cheers!
I just bought a digital thermometer, so hopefully this will make the process more accurate than the old 'kitchen' thermometer that I was using. Thanks for all the help.
