Stuck fermentation when using two kits and two yeast sachets

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CiderTropica

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I have made around 12 brews and the only one which didn't taste great was a Czech pilsner where I followed the instructions to the letter by adding a load of sugar. The result was a thin, dry, cidery beer which was almost undrinkable. Lesson learnt – I never added sugar again to any kit. Now, I add water up to the desired ABV, and add some dried malt extract if I want to raise ABV. All my beers have been fantastic since then.

The result of this approach is that a beer kit will now only create about half or two-thirds of the volume printed on the label. I'm fine with that, since lower volumes are easier to manage.

On two occasions, I bought two identical kits and emptied the entire lot into the FV to make a larger volume. After allowing to cool, I added both sachets of yeast simultaneously. In both cases, this resulted in a stuck fermentation with SG only falling around half of what it should have done despite the brew sitting in the FV for two weeks. On the first batch, I disturbed the yeast sediment to put it back in suspension. When this didn't help, I raised the temperature of the heating mat slightly. This worked okay and "unstuck" the fermentation.

On the second batch, these steps did not work, so I had to add another sachet of yeast (luckily I had a spare sachet of yeast appropriate for this style). This restarted the fermentation immediately and I ended up with a great product. However, this did increase the fermentation time to over three weeks.

My working theory is that dumping in two sachets of yeast into the top of the FV creates too much competition at the surface and the yeast goes dormant. My approach next time will be to add the first sachet then add in the second one a week later if fermentation appears stuck again.

Any thoughts on this? I realise two batches is not enough data points to draw conclusions.

I will add that I am adding one teaspoon of yeast nutrient per gallon to all my brews after getting the OG right.
 
I think this just shows that kit yeasts can be a bit crap. With enough viable yeast added at the start you should be able to ferment a kit out without the use of nutrient. It's not about yeasts competing with each other.

Bit of context would be useful. What kits were they, and what were the volumes and OGs of the beers?
 
I've had a few stuck fermentations in the past. Some of those have been when the yeast took off like the clappers, generated a lot of heat, and then stalled when the temperature dropped.
Here is the last one I did with S-04 that stalled at 1.020.
1732892932358.png


One potential explanation is that by brewing in a bigger batch, with more yeast, the temperature rose more than your 'single' batches and when it started dropping, the yeast stalled.

Or it could be something entirely different!
 
I've had a few stuck fermentations in the past. Some of those have been when the yeast took off like the clappers, generated a lot of heat, and then stalled when the temperature dropped.
Here is the last one I did with S-04 that stalled at 1.020.
View attachment 106292

One potential explanation is that by brewing in a bigger batch, with more yeast, the temperature rose more than your 'single' batches and when it started dropping, the yeast stalled.

Or it could be something entirely different!
Did you ditch the beer?

Funny enough, I've an issue with an S-04 batch right now. I've had issues with it before too.
 
I think this just shows that kit yeasts can be a bit crap. With enough viable yeast added at the start you should be able to ferment a kit out without the use of nutrient. It's not about yeasts competing with each other.

Bit of context would be useful. What kits were they, and what were the volumes and OGs of the beers?

What volume were the two kits made up to? Did you add any extra fermentables?

Batch 1
Coopers Half Ruby Devil's Porter (two identical kits used)
~18 litres tap water
~400g light DME
Total: 19 litres
OG: 1.062
After 13 days, and some faffing with the temperature/disturbing the yeast, FG: 1.016
(Previous batch with just one of these kits was FG: 1.012 after just 9 days)

Batch 2
Brewferm Winter Ale Kit (two identical kits used)
~100g light DME
Tesco Ashbeck mineral water
Total: 13 litres
OG: 1.068
After 13 days, SG: 1.030 – pitched another sachet of yeast (spare Belgian yeast from another kit)
After an additional 11 days, FG: 1.012

OK, I was just told it could easily create bottle bombs.

This second batch caused bottle bombs! First three bottles opened emptied half their contents over the kitchen counter. This is despite the SG being lower than the 1.015 expected SG in the kit instructions.
To counteract, I place a bottle in the freezer for 35 minutes before drinking. This is "off-style" since Belgian ale should not be served this cold. However, the large head protects the beer while it is consumed slowly, allowing it to warm up. It still tastes really good.
 
Ok, so you are starting with high gravities so that may result in a higher final gravity. The first brew has an attenuation of 74% which is probably about right. In the previous brew which went down to 1.012 I'm guessing the starting gravity was lower? Note: some yeasts are not great with higher alcohol beers.

Not sure why you are having a gusher on the brewferm kit.

Note: I brew beers at more sessionable levels of alcohol.
 
When going for higher ABVs, try to help the yeast by (a) oxygenating the wort, and (b) keeping initial gravity down.

(a) By pouring from height; by vigerous stirring (easier with drill degasser, but introducing air); air bubbler for two days or a burst of compressed oxygen. Perhaps your batch 2 problems, were from Tesco mineral water being low in oxygen.

(b) An initial OG below around 1050, can produce healthy, un-stressed yeast. So delay any brew sugar additions till fermentation starts easing off. Or, (when doing double batch) could even start with just one kit in nearly the full water amount, (less any water needed for dissolving 2nd kit). Adding (cooled) 2nd kit once fermenting vigorously (allowing good headspace for potentially huge krausen).

Thoughts on gushers, despite eventual FG (1012) being lower than target. Either, if bottled shortly after 1012 reached, lots of ferment CO2 could still be in solution, or FG might have dropped further, if left longer.
 

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