Total beginner with 1 gallon IPA kit - activity in fermenter has increased suddenly after 2 weeks, why?

[mrniaboc]

I'm a total beginner and really appreciative of any advice here. I'm making a 1 gallon batch of IPA from a kit. I brewed 16 days ago, and in the first 48 hours of the wort being in the fermenter it was bubbling away like crazy. It then settled down and I could see the liquid become less opaque and darker, as the yeast cake formed at the bottom. Today I went to look again as I had planned to bottle this evening, and it's more opaque again, and looks more active. What could be the cause for this. The last few days have been slightly warmer here (it's gone from ~20 degrees to 25 degrees), could it be the temperature variation?

In addition to this, I have been measuring the gravity with a refractometer every 3/4 days just to see how it was changing. After the first 3 days it had dropped to 1.034. Since then (almost two weeks now) it has remained at that value, so I thought fermentation must have been over? I have tested my refractometer on water and it seems to be calibrated well. Either way, poor calibration wouldn't account for the value not changing at all.

So, in summary, why does my wort suddenly seem more active again after 16 days, and why hasn't my gravity measurement changed for two weeks?

Thanks in advance for any help!

 

[Pirate_Pete]

Well, I'll be guessing here but I'd imagine that it stalled for some reason.
Maybe it got a bit cool overnight. Yeast likes a constant temperature.
A constant 20C would have been good. Although letting it get up to 25C isn't so good.
Then when the weather got warmer it kicked off again.
1.034 is too high to bottle. Depending on what fermentables and yeast you used it should come down a fair bit.
Mine usually end up around 1.010, with the yeast I use. But I know of people who use the kit yeast with Coopers beer who say they hit 1.008.

 

[honeymonster]

Try measuring with a hydrometer, if you have one.
Refractometers don't work very well with alcohol present, it screws with the readings, regardless of the calibration.
Refractometer before fermentation, hydrometer once it's started.

 

[peebee]

Being a "total beginner" probably saved you from panicking a week or more ago. But what "Pirate_Pete" says should be about right.

But what @honeymonster says also makes a good point: SG1.034 is way too high to bottle and you are using a refractometer but 1.034 looks suspiciously like a reading from a finished beer where the reading hasn't been converted to account for alcohol. Or it may be one of those refractometers with a "SG scale" which is completely useless once fermentation starts. Refractometers do work for fermenting and fermented wort. but the reading must be converted: There is no "ahh, it won't make much difference, I can't be bothered", it will make a lot of difference!

The temperature has risen to 25C which can make the most reluctant yeast have a crack at sugars it left behind first time around.

 

[mrniaboc]

Thanks for all the replies! Very helpful indeed. I will leave it for a little while longer, as it's clear the main culprit is probably the increase in temperature.

I use a refractometer instead of a hydrometer as I am only brewing 1 gallon batches to start, and I don't want to lose too much of the wort measuring it. I understand the gravity reading from a refractometer has to be adjusted once there is alcohol present, and I've found online calculators (and the actual formula) to help with this.

Thanks again!

 

[Pirate_Pete]

What I do is this.
I take a sample when I start the brew. I then leave it alongside the FV with the hydrometer in place.
Over a few days you can see it drop as the brew ferments.
It probably isn't that accurate, but I have a temperature controlled brew fridge.
I don't always take a final reading. If it ain't done after 14 days @ 20C there's something wrong!

 

[mrniaboc]

Just a wee update: Things have calmed down a bit again. Took an SG reading just there and it has finally lowered for the first time in about 10 days! So I guess the yeast had gone dormant for a while then got all excited again when it got slightly warmer? I'll leave it a few more days before bottling.

I used a couple of online calculators to adjust my refractometer SG reading, and it's coming out at about 1.016-1.018, which sounds pretty reasonable (OG=1.054).