Slow Fermentation and Not reaching SG

[jasonboll08]

I started a Porter a few weeks ago and had a problem reaching an end Specific Gravity lower that 1.022. Beginning SG was 1.052. The dry yeast took off rapidly at the beginning of fermentation and the air lock was very active for the first day and then slowed for a day and then stopped completely. At the end of the first 5 days I had a SG of 1.022 and the local brew store recommeded that I stir up the bottom of the fermentor because I may have flocculated out quickly and need to get the yeast back up into the brew to complete the job. Did that, didn't make a difference. Added another packet of yeast and had no more fermentation. Bottled the beer a few days later and we'll see what happens in a couple of weeks.

I started another beer yesterday (red ale, initial SG of 1.052) and the yeast took off again just fine, but now within 20 hours of pitching the yeast, the air lock is slowing down to almost no activity again, just like the Porter. I'm wondering if I do not have enough in there for the yeast to eat. Can anyone offer any insight as to what the problem might be?

 

[JVD_X]

Did you aerate the wort before pitching?

 

[Ecnerwal]

If it's beer, there's plenty for the yeast to eat. You can add yeast nutrient if it makes you happy, but that's utterly not needed for beer (mead and cider benefit from it).

Aerating the wort helps.

Having realistic expectations helps. Specific numbers quoted in recipes are often dubious, and always reflect someone else's particular process (assuming they actually brewed the recipe - otherwise it may reflect their software's guesses).

A porter inherently has a number of non-fermentables from the dark grains. Depending on the recipe there may be other non-fermentables.

As for the new batch, time of active airlock tells you little - you can have a long ferment that never gets very low, and a short one that goes terribly dry. Until you take a gravity reading you don't know, but there's very little reason to jump in early and take a reading.

If getting a low final gravity is important to you, choose a yeast with high attenuation, rehydrate it properly if dry, give it a good big starter if liquid, aereate the wort well, and if doing a mash, mash low.

 

[67coupe390]

If it's beer, there's plenty for the yeast to eat. You can add yeast nutrient if it makes you happy, but that's utterly not needed for beer (mead and cider benefit from it).

Aerating the wort helps.

Having realistic expectations helps. Specific numbers quoted in recipes are often dubious, and always reflect someone else's particular process (assuming they actually brewed the recipe - otherwise it may reflect their software's guesses).

A porter inherently has a number of non-fermentables from the dark grains. Depending on the recipe there may be other non-fermentables.

As for the new batch, time of active airlock tells you little - you can have a long ferment that never gets very low, and a short one that goes terribly dry. Until you take a gravity reading you don't know, but there's very little reason to jump in early and take a reading.

If getting a low final gravity is important to you, choose a yeast with high attenuation, rehydrate it properly if dry, give it a good big starter if liquid, aereate the wort well, and if doing a mash, mash low.

I agree 100% Your final gravity depends on a lot of things. Another simple way to see if your all fermented is to watch the airlock. Action greater than 2 mins means your done.

 

[jasonboll08]

I did aerate prior to pitching. I shook the primary back and forth for two minutes prior to pitching and stirred for another minute or two when I actually put the yeast in. I'm not going to take a SG reading until day 6 or so, and I don't feel like I'm hung up on numbers, per se, just concerned when I see such a dramatic drop off in air lock activity two batches in a row and wondering what is going on. I am used to seeing airlock activity for several days before such a drop off, not 20 hours like this batch and the last. How do I rehydrate the yeast properly? I just spread the yeast on top and gave it a good stirring.

 

[67coupe390]

To make a good yeast starer to hydrate the yeast I use two cups of 100 F water then add my dry yeast to it and cover. Making sure everything is sanitary. This is the first thing I do before I start boiling water for the mash.

 

[Ecnerwal]

There's no doubt more than one way - what I do is to put a half-cup of water in a 1-cup pyrex measuring cup, cover with plastic wrap and microwave until it boils. Then let it sit on the counter until it's down to 95-100F (sanitize the thermometer). Sprinkle the dry yeast on top and leave it alone for 15 minutes, then come back, stir it to suspend, and pour into the fermenter with the wort.

If going with "spring water is clean", you can just sanitize a cup and warm it to 95-100F - I'm starting with tap water and want it boiled first.
<edit-add>
Went and read the back of the package:

Danstar suggests 86-92F as a temperature range, and (after the 15 minute soak) avoiding temperature shock by adding a small amount of cooled wort every 5 minutes until the temperature in the measuring cup matches the temperature in the fermenter - otherwise as I stated.

Rehydrating for the entire two hours or more that you're brewing without providing some food (sugar) is dubious, in my understanding of the process - once rehydrated (15 minutes or so) the yeast want to eat.