I just finished my second Brew in a Bag (BIAB) and although everything went well, I had a difference in my anticipated FG. The recipe and Brewmate was giving me a finaly gravity of 1.014 but it finished fermentation at 1.010. Any reasons why the beer didn't reach the anticipated FG? I achieved my original gravity of 1.050 and I mashed at 66°C-67°C.

  • 3
    There is a certain degree of variability when it comes to the yeast's attenuation. Other factors include things like mash temperatures. What temperature did you mash at?
    – Scott
    Jan 7 '14 at 6:22
  • +1 to @Scott, who should have posted this as an answer. You should not expect your FG to exactly match your recipe or software; rather that is an estimate based on estimated attenuation of sugars by the yeast (how much of the sugars the yeast eat) in theoretical situations. Yeast often perform differently than the estimate (high and lower) in real-world conditions. Did you hit your target OG? Jan 7 '14 at 22:19
  • Indeed if following a cake recipe you wouldn't expect to get exactly 1.5 inches of rise on a sponge cake simply as that is what the original author got with a different brand of ingredients of different ages mixed with different mixers and cooked in different ovens at different altitudes. It is the same here, you will get something very similar to the original, but it will not be exactly the same.
    – Anigel
    Jan 9 '14 at 15:26

A possible cause could be when you took you SG the wort would have suspended particles from the malts. These particles in solution will effect the density of the wort and your reading. When left to settle by the time of FG reading these particles are no longer in suspension.

The density of a sediment-water suspension depends on the concentration and specific gravity of the sediments present in the mixture. If the suspension is allowed to stand, particles will settle out of the suspension and the density of the sediment-water suspension will decrease.

O.004 is quite a small difference (+0.5% ABV) and being lower shouldn't be anything to worry about just slight more alcohol. With wines/ciders it can make taste more dry.

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