Why only 73% attenuation

[eddiewould]

Hey,

I only saw 73% attenuation (1.069 - 1.018) with this grain bill - single infusion mash at 64c. Wyeast 1272 2L starter, fermented at 16.5c. Was expecting a bit more attenuation. Have tried raising the temperature (up to 21c) and swirling but think it's done?

5.00 kg Gladfield Ale Malt 70.4 %
1.00 kg Gladfield Munich Malt 14.1 %
0.30 kg Gladfield Roasted Wheat 4.2 %
0.20 kg Gladfield Dark Chocolate Malt 2.8 %
0.20 kg Gladfield Light Chocolate Malt 2.8 %
0.20 kg Gladfield Medium Crystal Malt 2.8 %
0.10 kg Gladfield Brown Malt (178.0 EBC) 1.4 %
0.10 kg Gladfield Roast Barley 1.4 %

Malt details are here: http://www.gladfieldmalt.co.nz/the-malt

I have a suspicion as to what the problem might be - which is that I think I may have decanted the liquid from my starter too early (only cold-crashed for one day before decanting). That would select for flocculative cells (not to mention reducing the cell count). Having said that, it was a very vigorous fermentation.

 

[kh54s10]

That yeast shows 72-76% for the range. You have a lot of dark malts in that recipe. I think 73% is about what I would expect.

 

[chickypad]

That yeast shows 72-76% for the range. You have a lot of dark malts in that recipe. I think 73% is about what I would expect.

Agreed. What was your mash temp?

 

[eddiewould]

Mash temp was 64c (147.2f)

 

[didinho]

Hey,

I only saw 73% attenuation (1.069 - 1.018) with this grain bill - single infusion mash at 64c. Wyeast 1272 2L starter

sounds OK for that yeast with all those dark malts. how long did it ferment? when I doubt it was not at FG yet, I let it stay in the secondary fermentor for few days more then I bottle.

 

[eddiewould]

Fermented for one week. Gravity was stable between day 5 and day 7. It's sitting at 21c for another 5 days or so to condition before I crash cool it.

Tastes good anyway - and I've added some cold-brewed coffee to it which will lower the gravity a little.