I have now done 2 brews using my herms setup and both brews stopped short of the predicted final gravity.
the first was a bitter from g wheelers book that I have brewed several times before using my thermopot mash tun but this time although mashed at 66 and getting my sg spoton after adding liquor to makeup for excessive boil losses the ferment stopped at 1014 instead of 1012, and my second brew mashed at 68 og 1032 has stopped at 1014(after 14 days in fermenter) when according to the book 1006-1008 was the predicted final gravity.
both brews have been fermented using sa04 yeast in fridge at 19 degrees
I have not had this problem before the last 2 brews which incidently are the first 2 using the herms setup(is this a coincedance)
I have checked the calibration of pid in iced water so am happy the temperatures are ok
I realise these are only predicted final gravities but with a mild of 1032 stopping at 1014 it makes it a very weak beer
any ideas please
not reaching predicted final gravity
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- Hollow Legs
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Re: not reaching predicted final gravity
hi paulg
did you rehydrate the yeast ?
how do you oxygenate the wort ?
how do you control ferment temp, have you tried increasing temp a couple of degrees, or tried rousing the yeast ?
cheers
beert
did you rehydrate the yeast ?
how do you oxygenate the wort ?
how do you control ferment temp, have you tried increasing temp a couple of degrees, or tried rousing the yeast ?
cheers
beert
Re: not reaching predicted final gravity
Obviously the question I would ask is how are you controlling the mash temperature now, and how did you control / measure it prior to herms?
i.e. If you used a thermometer pre Herms and are using a PID for Herms it could be:
1) Your PID hasn't been calibrated so you are mashing hotter than you think
2) Your Thermometer was reading high thus you were previously mashing lower than you thought
3) A mixture of 1) and 2)
I found I'd been mashing 1C low previously after I calibrated my PID after moving the BIAB Herms.
i.e. If you used a thermometer pre Herms and are using a PID for Herms it could be:
1) Your PID hasn't been calibrated so you are mashing hotter than you think
2) Your Thermometer was reading high thus you were previously mashing lower than you thought
3) A mixture of 1) and 2)
I found I'd been mashing 1C low previously after I calibrated my PID after moving the BIAB Herms.
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Re: not reaching predicted final gravity
If you mashed at 68 C I'm not surprised your fg was high.
Best wishes
Dave
Dave
Re: not reaching predicted final gravity
dave s
I calibrated my pt100 for herms and my thermometer and an other pt100 that I sat in the mash(only as an indication of temp) all in an ice /water mix and all at 0 degrees then during mash moved the offset of herms pt100 by 1.5 degrees to match the pt100 sat in mash (my herms pt100 is on the exit of pot about 8 inches of insulated silecone tube between herms and mash tun)
it is possible that before I was mashing at a lower temp than I thought as I was taking readings with digital thermometer at various places within the mash and if it was at 66 or 65.8 I was thinking ok thats good enough.
just checked recipe for the mild and it was mashed at 67 not 68 but bitter was definitely at 66 ,before I had mashed everything at 66 but because mild is a low gravity drink I guess that is why 67 is recommended to retain some more body in the beer
I now suspect my mash tun temperatures are the problem producing a less fermentable wort .
I will have to check more carefully next time that the mash temp is as per the setting on the pid and not higher in case it needs the offset changing a little lower
I am still learning with the herms setup.
thanks Paul
I calibrated my pt100 for herms and my thermometer and an other pt100 that I sat in the mash(only as an indication of temp) all in an ice /water mix and all at 0 degrees then during mash moved the offset of herms pt100 by 1.5 degrees to match the pt100 sat in mash (my herms pt100 is on the exit of pot about 8 inches of insulated silecone tube between herms and mash tun)
it is possible that before I was mashing at a lower temp than I thought as I was taking readings with digital thermometer at various places within the mash and if it was at 66 or 65.8 I was thinking ok thats good enough.
just checked recipe for the mild and it was mashed at 67 not 68 but bitter was definitely at 66 ,before I had mashed everything at 66 but because mild is a low gravity drink I guess that is why 67 is recommended to retain some more body in the beer
I now suspect my mash tun temperatures are the problem producing a less fermentable wort .
I will have to check more carefully next time that the mash temp is as per the setting on the pid and not higher in case it needs the offset changing a little lower
I am still learning with the herms setup.
thanks Paul
- Eric
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Re: not reaching predicted final gravity
I'll suggest it is due to your new system.
Previously your mash would cool, leading to better conditions for the beta amylase. That converts complex sugar produced by the alpha amylase into fermentable sugar.
Now you have a system that allows you some contol over the process, but used in a way that has not been to your advantage. Have a bit study of that below.
As for the mild, drink and enjoy.

Previously your mash would cool, leading to better conditions for the beta amylase. That converts complex sugar produced by the alpha amylase into fermentable sugar.
Now you have a system that allows you some contol over the process, but used in a way that has not been to your advantage. Have a bit study of that below.
As for the mild, drink and enjoy.

Without patience, life becomes difficult and the sooner it's finished, the better.
Re: not reaching predicted final gravity
In answer to other questions
I did not rehydrate the yeast but did pitch 1 1/2 sachets as i dropped the other on the floor
the wort was airiated using paddle and whisking /stirring
I control the fridge with atc800 and have increased the temp to 20 degrees for 2 days but nothing has changed
my pids and thermometer were calibrated in ice/water at 0 degrees so I am reasonably happy they are accurate although the pt100 on the output of the herms pot offset I need to check as maybe it is too much 1.5 degrees .The pot is connected to the mash tun by about 8 inches of silicone pipe insulated with pipe lagging
yes eric you are probably correct looking at that diagram if I was a little too high mash temp then that would explain it
I did not rehydrate the yeast but did pitch 1 1/2 sachets as i dropped the other on the floor
the wort was airiated using paddle and whisking /stirring
I control the fridge with atc800 and have increased the temp to 20 degrees for 2 days but nothing has changed
my pids and thermometer were calibrated in ice/water at 0 degrees so I am reasonably happy they are accurate although the pt100 on the output of the herms pot offset I need to check as maybe it is too much 1.5 degrees .The pot is connected to the mash tun by about 8 inches of silicone pipe insulated with pipe lagging
yes eric you are probably correct looking at that diagram if I was a little too high mash temp then that would explain it
Re: not reaching predicted final gravity
I just use a calibrated PID with the sensor on the return where it enters the mash tun.
It's worked brilliantly for me upping my BIAB efficency from 65 to 70%. Absolutely no need to take measurements elsewhere providing the pump is continuous and at a decent rate. Mine does 5L per minute during a mash using BIAB so recirculates / reheats the whole wort in around 7 minutes for a 23L batch.
My recent RIS mashed at 66C went from 1.088 to 1.018 as and example of the fermentables obtained.
It's worked brilliantly for me upping my BIAB efficency from 65 to 70%. Absolutely no need to take measurements elsewhere providing the pump is continuous and at a decent rate. Mine does 5L per minute during a mash using BIAB so recirculates / reheats the whole wort in around 7 minutes for a 23L batch.
My recent RIS mashed at 66C went from 1.088 to 1.018 as and example of the fermentables obtained.
Re: not reaching predicted final gravity
on thinking more about this I think the problem is that as I have the pid set with an offset of 1.5 degrees ,when I set the pid to 67 the actual temp at the herms output where the pt100 is is +1.5 degrees ie 68.5 even though the grain bed is only at 67 .So as the wort passes through the herms coil it is being heated too hot and in effect mashing at the higher temp
Does this logic seem correct?
what do other herms users set there pid up as? bearing in mind my herms coil is about 8 inches of insulated silicone pipe connecting to the mash tun and the wort is returned to whirlpool around the top/side of mash tun(thermopot)
Does this logic seem correct?
what do other herms users set there pid up as? bearing in mind my herms coil is about 8 inches of insulated silicone pipe connecting to the mash tun and the wort is returned to whirlpool around the top/side of mash tun(thermopot)