Fermentation stuck at 1.020 from 1.040 what should I do?

[benkbenkbenk]

I made this recipe http://thehomebrewforum.co.uk/viewtopic.php?f=14&t=46622 two weeks ago. The fermentation has been stuck at 1.020 from an OG of 1.040 for the last week. The fermentation started,very vigorously, but then the krausen all fell away after about 72 hours.

It was my first time using this Mangrove Jacks yeast, so I think it could be that, and I have read about it having a low attenuation for others online. I also put a bit too much chocolate malt in the recipe which I have heard can make fermentations stick. I tried raising the temperature for the last week with hot water bottles and a sleeping bag, but there has been no change.

The question is, do I try to restart the fermentation or not? It will come out at about 2.7% when I was aiming for more like 4%.

If I do try to restart it, should I do this by

a) Stiring with a sterilized spoon
b) adding more of the same yeast
c) adding a different yeast

or should just chuck in my rum and oak chips today and bottle next weekend as planned?

Thanks!

 

[rpt]

I would first give it a stir. You want to rouse the yeast - get the flocculated yeast back into suspension - but not splash which will cause oxidisation. If this fails to bring the gravity down then you can pitch more yeast. Most of the flavours will already have developed so it probably doesn't matter what yeast you use (as long as it's a beer yeast). Ideally you want to make a starter and pitch at high krausen but as long as you rehydrate the yeast you are probably ok as your wort isn't too alcoholic.

 

[mike77]

I would rouse the yeast a little and perhaps up the temp a bit. What temp is it at? Their website says between 18-22 degrees

 

[rpt]

That's a good point about the temperature. At this stage you can safely raise the temperature to 24C which should help attenuation.

 

[benkbenkbenk]

Yeah I tried raising the temperature, its been mostly around 18C but I suppose it may have dropped lower at night. I've just pulled the fermenter out of the cupboard to give it a stir and there is hardly any trub, probably about 5mm at the bottom of a 25 litre FV. Normally I'd expect to see about an inch there. Could this be due to poor aeration at the start?

 

[calumscott]

viewtopic.php?f=30&t=15082

:thumb:

 

[benkbenkbenk]

Thanks, did a search but somehow didn't come across that thread. Really useful!