Inconsistant Fermentation

[brewologist]

Hi All,

I hope some of you can help me out with whats going on with my fermentation. This is my fist time using a fermenting freezer and for the first 6 or 7 days of the ferment I was regulating the temp with frozen water bottles and turning the freezer on manually to keep the temp at 18c. Yesterday I finally got my stc wired up and plugged the freezer and heat mat into it so the temp should be better regulated now.

So anyway I brewed this recipe and put it down on the 2nd of Jan and one FV reads 1.010 and the other 1.019. I started with a OG of 1.069. I over shot the 1.060 I was going for. I think due to the hot weather my mash temp and boil off were a bit higher than I bargained for. Also the batch with the higher gravity took a bit of traub out of the kettle and had a liter less than the one sitting on 1.010 so I don't know if thats causing the difference.

The FV's have been kept at the same temp but their gravities are very different. Is there a reason for this and some way to ensure it doesn't happen in the future?

This was my recipe.

Recipe Specifications
--------------------------
Boil Size: 55.97 l
Post Boil Volume: 44.72 l
Batch Size (fermenter): 41.00 l
Bottling Volume: 38.20 l
Estimated OG: 1.062 SG
Estimated Color: 12.4 EBC
Estimated IBU: 39.9 IBUs
Brewhouse Efficiency: 70.00 %
Est Mash Efficiency: 73.4 %
Boil Time: 90 Minutes
Ingredients:
------------
Amt Name
6.00 kg Golden Promise (Simpsons) (3.9 EBC)
5.00 kg Pale Malt, Traditional Ale (Joe White)
0.50 kg Caramel/Crystal Malt - 30L (59.1 EBC)
25.00 g Centennial [10.00 %] - Boil 60.0 min
15.00 g Galaxy [14.00 %] - Boil 20.0 min
15.00 g Topaz [17.00 %] - Boil 20.0 min
1.00 Items Irish Moss (Boil 10.0 mins)
15.00 g Cascade [6.20 %] - Boil 5.0 min
15.00 g Centennial [10.00 %] - Boil 5.0 min
15.00 g Galaxy [14.00 %] - Boil 5.0 min
10.00 g Citra [12.00 %] - Boil 5.0 min
5.00 g Topaz [17.00 %] - Boil 5.0 min

 

[kelbygreen]

the one reason its happening you did not give us any information on! YEAST!

What was it?
are they both the same yeast?
How did you add it?

You will find just coz you get a pack or yeast that it will work 100% the time. There is prob 100's of reasons why it happened but your best bet is rousing it a little raising the temp to 20 and see how it goes.

You can control the yeast one your end to a point but if its been mishandled or is out of date or been shocked before you get it then your already struggling and not know it.

being in a freezer you may of had colder spots where the cooling lines are so it might of cooled one to much. Again there is prob 100+ reasons and you will prob never know unless it happens again.

 

[brewologist]

Thanks kelbygreen,

It was US05. Always stored in the fridge. I pitched it dry no starter. I'm pretty new to brewing. Maybe its time to get into yeast starters.

Cheers,

Gav.


Edit: Also the one with the high grav spewed its krausen while the other was a gentler ferment. Don't know if that changes anything tho?

 

[kelbygreen]

did you loose alot out the fermenter? Maybe it lost to much and didnt have enough to keep going. I would warm it up a bit and rouse without splashing see if it will start again. Some time some can take longer then others, it seemed like it started off well though so thats good not sure why it would be that far off unless it stalled some how

 

[jakethesnake559]

Where are you measuring the temp?
If you had a slightly warmer temp in one of the fermentors, it would ferment out quicker.

 

[brewologist]

did you loose alot out the fermenter? Maybe it lost to much and didnt have enough to keep going. I would warm it up a bit and rouse without splashing see if it will start again. Some time some can take longer then others, it seemed like it started off well though so thats good not sure why it would be that far off unless it stalled some how

I didn't lose much out of the fermenter. Maybe a cup or so as it just covered the top of the lid.

Where are you measuring the temp?
If you had a slightly warmer temp in one of the fermentors, it would ferment out quicker.

The probe is taped to the side of the fermenter under a couple of layers of cut up stubbie holder. It is ton the one with the slower ferment. From what I've read this seems to be the easiest way to get a temp reading without putting the temp probe into the wort.

The initial temp over the first few days was probably somewhere around 15 - 16c cause I had no way of getting an accurate temp. I only had the usual temp gauge on the side of the FV.

The freezer is now set to 20c so I'll leave it there for a couple of days and then take another reading. I'm probs just stressing out over this batch as my previous one (42L - 120 pots :huh: ) got tipped down the drain as I had no way to regulate the temp. I tried putting it in the bath tub with ice blocks etc but couldn't get it low enough to pitch. Loving the freezer with stc.

Cheers for your replies,

 

[Screwtop]

Were your fermenter volumes the same, I assume you pitched one pack of yeast to each. At 1.069 one pack would be enough for around 16 - 17 litres. Above this volume you would need to use more dried yeast for the correct pitching rate.

Screwy

 

[brewologist]

Were your fermenter volumes the same, I assume you pitched one pack of yeast to each. At 1.069 one pack would be enough for around 16 - 17 litres. Above this volume you would need to use more dried yeast for the correct pitching rate.

Screwy

I had 20L in one and 21L in the other. I will pitch more yeast if the gravity doesn't change over the next couple of days. Thanks for the tip.

 

[yankinoz]

How much yeast did you pitch in each FV?

Another possibility is that you oxygenated/aerated one batch better than the other.

Either way it's possible the yeast in one batch did not multiply enough in the aerobic phase of fermentation to complete the fermentation later. The risk goes up the higher the starting gravity. For dry yeast at your gravity, many brewers woud use 1 1/2 to 2 packets on each or else a yeast starter.

But try the above suggestions. If the final gravity readings stay the same, keep in mind that the unfermented sugars in the 1.019 batch might ferment later in bottles or kegs, especially if those get warm. I've had that happen and ended up with overcarbonation, though no explosions. Your difference between 1.012 and 1.019 is equivalent to about 300 g of fermentable sugar in a 20L batch, is about double what you'd add for priming to fairly high carbonation. That's a lot of CO2.