Beers Finishing at 1.020

[Covey]

Hi Guys,
I ve had a few beers that have finished well short of the mark, one is a Irish stout mashed @ 65, i thought it might be a bit cold in the location where its been so i ve moved it to a warmer location roused the yeast for a week but it has'nt drop a point. Its tastes find but a tiny bit sweet, i had hoped for a dry finish. would re-pitiching help. what has caused this any ideas. (used and rehydrated USO4)
Thanks

[Oh Crap]

What was the OG?

[DEMPSEY]

How healthy is your yeast and are you pitching enough.

[Covey]

The OG was about 0.1060, pitch a full packet of yeast into lukewarm  500mls of sugary water (25C) for 2hrs you can see the yeast kicking off before i added it to the fermenter. If you mash high will you have a lot of unfermentables left over. Im brewing in a BIAB in Boiler. Have checked the hydrometer too. Would a high mash temp cause this

[Sorcerers Apprentice]

In addition to previous suggestions
Had the mash fully converted - did you test with Iodine?
Did you oxygenate the wort sufficiently
Is this first generation yeast, if not did you add yeast food?
It is possible to repitch, I would suggest take a litre of wort whip it up well to add O2 and pitch into this, if there are signs of fermentation, then there are fermentable sugars left in the wort, if not then the yeast has reached maximum attenuation and won't convert any more sugar regardless of how much yeast you add.

[DEMPSEY]

You mashed at 65 so that's not high but are you sure that was correct

[Covey]

is it enough to let you beer pour into the fermentation vessel to aerate the wort. Im not going to aerate the wort at this stage incase i oxidize it. I have start to aerate the wort on my next batches with the paddle stuck in the drill and the beer has taken off in less than 12 hours. So i will be doing this from not on. On another note i have under carbed bottle beers have not idea why, i'm doing everything normally(prime 500ml botle with a 1 and 1/2 carbonation drops.) its been  4 weeks and a reg IPA at 5 % is still under carbed. Think its all down to the low temp in my Brewery (Utility room). Going to map it to see what the temp is like, thought it was around 16-19 but it must be lower than that

[Covey]

Pretty sure it was 65, and i mashed the shit out of it and was happy with it, i use two thrmocouples with outwell stuck into the mash so when they are agreeing at the temp i need i take it to be mashed

[Qs]

Don't use sugary water to rehydrate your yeast, just use normal water and don't leave it for 2 hours, 20-30 minutes is plenty.

[nigel_c]

Work backwards and eliminate possible problems.

Boil up some water and check your termineter is reading 100c.

Check your hydrometer in water at the correct temp and make sure it reads 1.000

The beer could be grand and it's just your hydrometer readings could be off.

[winstonia]

Isn't 1020 the norm for stouts unless you were aiming for a dry stout?

Any oats used?

[Alex Lawes]

I've had this issue and this is how I sorted it.

S-04 has a habit of not finishing up due to it being super flocculent. I've had beers stop there with that yeast that should have come down as low as 1.008. This over flocculation can lead to high levels of diacetyl as well.

S04 needs zinc, as do all yeasts. For some reason I've found that S04 needs a little bit more. You need to make sure it has enought nutrient if you water doesn't have that particular micronutrient. The council will usually try to deliver you water with zero zinc levels but you actually need 0.1-0.5ppm. Half a teaspoon of yeast nutrient or a tiny bit of a zinc tablet from the chemist will help. Add it either at the beginning of the boil or make a shot of liquid and dash it in when you pitch your yeast.

Secondly, it's good practice to rouse S-04 for lower ABV beers (3-5%). The fermentation isn't as lively for these as HG ones which tend to keep the yeast in suspension easier. When you see the yeast is starting to drop, give it a gentle stir to re-suspend with a sanitised paddle and it should help, but be careful not to introduce more oxygen. This will help clean up diacetyl as well.

You'll very rarely get full attenuation from S04 in its first generation but as you re-pitch you'll notice it dropping that bit more. Expect it to be 1-3 gravity points out on gen1.

I hope this helps.

[Qs]

They're some good tips Alex. I'd recommend just shaking the carboy rather than opening and stirring to rouse the yeast though. I often shake to rouse the yeast and my hope is that the bed of CO2 produced from the fermentation to that point will protect my beer from oxygen. Opening and stirring will certainly allow the CO2 to be replaced by oxygen.

Your point on needing yeast nutrient corresponds with rehydrating as the manufacturer recommends too. There are nutrients in with most dried yeasts and creating a small starter will waste some of them. Thats why just rehydrating is recommended.

[Covey]

Ok So as i didnt have any Yeast nutrient i read up and use what i d had to hand which was Champagne yeast. I boiled it in a 3/4 cup of water about to 1/2 cup. Then added ot and and gently stired up the yeast. So let see what happens, thanks for allt eh adivce guys..Every days a school day

[irish_goat]

Ok So as i didnt have any Yeast nutrient i read up and use what i d had to hand which was Champagne yeast. I boiled it in a 3/4 cup of water about to 1/2 cup. Then added ot and and gently stired up the yeast. So let see what happens, thanks for allt eh adivce guys..Every days a school day

When you're done, freeze some of the yeast at the bottom of the FV and you can bung that into the boil next time for handy (and free) yeast nutrient.