Ambient temperature drop and effect on fermentation.

[ericmark]

During the winter my fermentor was placed next to the radiator in kitchen so kept quite warm. As summer arrived central heating went off but ambient temperature in house 18 to 22 degrees C but as winter is approaching again the central heating has not kicked in but fermentor down to 16 degrees C with a Geordie bitter in it around the time where I expect to bottle.

The air lock bubbles have reduced to one a minute and s.g. around 1.010 (start was 0.046) but temperature is also of course changing the hydrometer reading. I have placed a sample under floor heating tile under the fermentor which draws 16W and wrapped it in my florescent jacket to try and raise the temperature back to 18 – 24 degrees recommended by the kit instructions, but how important is the temperature? I was expecting the s.g. to drop to 0.005 which the instructions say should be shown over 2 days, but with 0.002 being likely due to temperature drop I am uncertain.

I did an experiment with the two hydrometers I have, and the temperature change resulted in very different readings between the two both showed same at 60 degs F but varied widely as temperature was dropped and increased. If it were not near the end I would not worry but the temperature drop is just at the wrong time in process.

I am sure many others have the same problem so any ideas how to assess if ready to bottle when air lock and hydrometer seem to give unreliable results due to temperature change?

 

[Papa G]

Hi ericmark, hydrometers are set to read true at a set temp, normally 20 degs c.
To correct for different temp of liquid, go to the calculators, link top left of page, and use the Hydrometer Temperature Correction Calculator. This will adjust for different temps.
Hope this helps.

 

[ericmark]

Thanks I had looked at that idea my glass hydrometer is calibrated at 60 degs F and says no significant error if within 2 degs but this is of course degrees F not C. Really it does not matter what the reading is as long as the same for three days but that's the point temperature change means hard to work out if changed or not.

The plastic hydrometer also says 15.4 degrees C or 60 degrees F however the change with temperature goes the reverse to that with glass which alerted me to the problem in not all hydrometers alter the same with temperature variation. It needs to be conversion specific to that hydrometer not a general one.

With changes of reading over 0.002 likely one can see it as being true, but as it nears complete, the readings are very close so it would seem only option is to warm it back up again. Clearly this will take some time 16W is very little and 6 gallons is a lot of liquid in hind sight I should have put a body warmer around it far earlier so now it's just a case of waiting.

The fact that bubble rate has already increased makes me think not ready for bottling yet. I am learning but very slowly!

 

[ericmark]

Well I can now report that 16ºC was too low. I put a jacket around the brew and at 18ºC the bubbling restarted at a rate of one every 30 seconds was going on 3 days holiday so could not really try heating. On return used a sample underfloor heating tile designed to demonstrate how good underfloor heating is. It draws 18W this has risen the temperature to 22ºC and the activity back to one bubble every 20 seconds and the S.G. dropped from 0.010 to 0.006 disturbing brew to use hydrometer clearly still very active.

Easy in hind sight but clearly had I left at 16ºC it would not have altered enough for me to read and I would have bottled too early. The instructions state 18º-24ºC this is now clearly important and 16ºC was too low. Also simply putting a body warmer around the beer has risen it by 2ºC so clearly there is energy released just from the process of brewing which in turn means the warmer it's kept the warmer it gets it's self.

So I will be monitoring this brew so I can use the knowledge in the future to know when to cover and when not to cover. The more active mild started two weeks after the bitter and put in a body warmer at the same time is holding temperature nicely.

 

[bobsbeer]

At 16c the yeast activity would have reduced significantly depending on the yeast. The temp range of 18-24 is a recommended range for the yeast strain. All strains have their specific range. If it gets too low they stop until they warm up again. 18-22 is probably the best range, so warm it up a bit and be patient. It will get there.

 

[ericmark]

Thanks. Been a lovely day really warm so now looks if ready to bottle tomorrow.

 

[ericmark]

Well now really scratching head. Hydrometer reading has risen from 0.006 sg to 0.010 sg the temperature has also risen from 16 degsC to 20 degs C and the airlock activity has increased from 60 seconds a bubble to 25 seconds a bubble over a 6 day gap. Warm day so removed the covers and allowing match the room temperature which is nearly the same anyway. Had I not taken pictures of the hydrometer readings I would have put it down to miss reading the hydrometer but looked at pictures and yes the reading has risen? Started 4th Sept so 18 days in fermentor for a kit beer which says about a week. Goodness knows what this will do to the taste?

 

[broken robot]

Don't worry about it. If it's still bubbling leave it, no harm will come to your beer. Palmer says that it can sit on the yeast for over a month without any harm coming to your beer. In my limited kit experience, those kit instructions are to be taken with a pinch of salt.

 

[ericmark]

Given up bottled but used plastic for all but two so I can feel the pressure. Much of the gas seemed to release during the transfer I had to keep the syphon running quite rapid to prevent loss of syphon due to gas released.

As with the other guy on here with same problem only time will tell.