measuring temp in the wrong place?

[tomaso]

I've got about 40 BIAB batches under my belt and am quite happy so far with the results except for the problem that almost all my beers finish too high (about 4-5 points).

It's a lack of awareness on my side but just recently I've noticed that I'm always measuring the temp either on the lower (but not bottom!) end of the pot with a probe or even higher up with a short electrical thermometer. I use a 15L (4 Gallon) pot and usually have 3kg (6,5 pounds) of grain in 12L (3 Gallons) of water.

And just recently I stuck a longer mercury thermometer all the way down into the grain bed and the temp there -o wonder!- was about 2C higher than measured further up the pot. Same with pushing the probe down into the grain just above the bottom.

Another thing is that until now I've always left the pot on the stove (it's induction) which keeps warm instead of putting it aside....

So I'll definitely try and do a few batches measuring from the bottom and removing the pot from the warm stove but would be glad if some of you more experienced guys could tell me whether I've been doing it wrong all along...

Thx

 

[andrewf1985]

Are you raising the temperature at the end of fermentation to eeek those last few points out? I use a mercury style thermometer and put it in as deep as i can read my required temperature, check a couple of spots abd if it varies, give it a good stir. I leave it be with no temperature control so you could be getting a small rise from the induction hob. Maybe try a batch with the use of that. Also, as your using BIAB, you could stir at intervals during the mash so the temperature stays even through your mash

 

[tomaso]

I raise the temp a bit but I also use fast ferment samples and they finish too high as well. I do stir the Mash.

 

[TexasWine]

It's official. I hate the mobile app. Had a nice long response typed out and it said I didn't have permission to access the forum. Grrr...

Here's the short version.

One, make sure you're mercury thermometer and probe thermometer always read the same temp. Mercury could be reading 2C higher all the time.

Two, when I would stove top BIAB I would either insulate like crazy or pop the pot into the warm (not hot) oven. You could run a test with plain water to see if the induction top is increasing the temp after being turned off. I would wager that it is.

Three, temp stratification is unavoidable unless you're constantly stirring. Don't fret too much about it unless you're adding heat during the mash, then stir like a mad man. But note, if you insulate well there will be no need to add heat during the mash if you're just trying to maintain a single temp.

Last thing, yeast. Have you checked to see if your yeast attenuation is within the manufacturer's specs? Are you using a starter? Temp control?

Hope something here helps.

 

[tomaso]

It's official. I hate the mobile app. Had a nice long response typed out and it said I didn't have permission to access the forum. Grrr...

true that!!! Happens so often to me. And while we're at it... Beersmith mobile version also sucks

Here's the short version.

One, make sure you're mercury thermometer and probe thermometer always read the same temp. Mercury could be reading 2C higher all the time.

Two, when I would stove top BIAB I would either insulate like crazy or pop the pot into the warm (not hot) oven. You could run a test with plain water to see if the induction top is increasing the temp after being turned off. I would wager that it is.

Three, temp stratification is unavoidable unless you're constantly stirring. Don't fret too much about it unless you're adding heat during the mash, then stir like a mad man. But note, if you insulate well there will be no need to add heat during the mash if you're just trying to maintain a single temp.

Last thing, yeast. Have you checked to see if your yeast attenuation is within the manufacturer's specs? Are you using a starter? Temp control?

Hope something here helps.

Thanks for the answers.
Good tip about heating the water... I'll try that.

My probe actually reads 2C lower than the mercury one and the electrical one so I've just been trusting those two and accounted for +2C on the probe one...

I am insulating the pot with aluminum foil and a towel but heat loss doesn't seem to be my problem.

the yeast is the other potential culprit.... just posted in the yeast forum about up to now having rehydrated my dry yeast in extract instead of water. But still, i've pitched a full pack of dry safale (eventhough rehydrated in extract) into only 3 gallons of wort and it still finished too high...

I do use temp control. Used liquid yeast only a few times and was also too high. Maybe my starter wasn't big enough though... but have the feeling it's more likely the mash than the yeast, unless the extract rehydration is such a big issue....

 

[wilserbrewer]

I always stir well prior to checking temp, otherwise anybody's guess

 

[tomaso]

The problem seems solved. My last 4 batches have all finished at their expected FG(or one point above). The changes I've made have been to remove the pot from the induction stove after dough in and measure the temp further down in the Pot where most of the grist lies. Haven't tried Texas wine's water heating test yet but I'd also say that the warm stove would keep heating the Pot if not removed and that that probably was the main culprit.
The temp further down in the pot is different as well though by some 2C sometimes...

So thx for your help and brew on!

 

[TexasWine]

Congrats! You're a busy brewer if you've done four batches since the original question.

 

[tomaso]

Thanks. It's cause I'm going away now for a month with no brewing so had to make up for lost time

 

[andrewf1985]

Man on a mission, getting the summer/autumn stocks sorted. Glad its sorted