Higher Than Expected FG

[Steve SPF]

So, my stout went into the fermenter last Sunday and the brew went relly well, nailed all the temps and was a very clean day.

OG was 1058 and the recipe called for 1059 so I was happy there as well. I set the temp to 18° and left it there until Friday, I bumped it up to 19° and gave it 24 hours at that hoping that it would ferment out a little more but today we are only at 1015 and I think it's done. The recipe called for a FG of 1010 so I'm quite a way off, why would I miss the FG by quite so much?

I'm not too worried because the beer tastes great now but if I have something wrong I would like to figure out what.

Thanks for help.

 

[philjohnwilliams]

Was this an extract or all grain batch? I have found it is not unusual for extract batches, especially if made with older LME to finish higher than expected.

 

[Steve SPF]

All grain.

Edit: Looking at it, last time it finished at 1022 and the recipe that I took my recipe from called for a FG of 1018 so maybe 1015 is it?

If that's the case then maybe my question is why would the recipe calculator here give an FG of 1010?

As I say, I'm not too worried but I am curious and want my results to be predictable so am trying to understand.

 

[Megary]

Assuming I'm doing the math correctly (always a big assumption):
If the recipe called for an OG of 1.059 and a FG of 1.010, that's 83% attenuation. What yeast did the recipe call for and what is its average attenuation?

 

[Mase]

Some yeasts can get stuck around that gravity. Give it a swirl and wait for three days of the same gravity reading before you call it.

 

[Steve SPF]

There's maths involved? Here's me thinking it's witchcraft!

The yeast is Safale US 05, apparent attenuation 78-82% according to their website.

 

[Mase]

There's maths involved? Here's me thinking it's witchcraft!

The yeast is Safale US 05, apparent attenuation 78-82% according to their website.

Should finish around 1.012 @ 80% attenuation. 80% of 59

 

[Steve SPF]

Brill. I can understand maths so that's a neat bit of knowledge.

 

[716Brewer]

Some yeasts can get stuck around that gravity. Give it a swirl and wait for three days of the same gravity reading before you call it.

Agreed. I had to do this with the last stout I brewed. Brought it right down.

 

[Bubba Wade]

Besides yeast attenuation, another factor is the percent of fermentable sugars in the mash. Different mashing techniques and temps will yield different proportions of fermentable sugar. You can have two worts of the same OG, use the same yeast, and get a different FG if the mash was a bit different..

 

[Mase]

Great point!

 

[Steve SPF]

All interesting; so much to learn.

I looked at the recipe here again and it seems to be telling me that I should have used a starter so that's something to look at as well.