I use a fine nylon mesh grain bag and have noticed that there is a difference in wort temperature inside the bag versus outside the bag. For example, when I'm mashing and I take a temperature reading with my thermometer of the wort inside the BIAB bag, it might read 65°C, BUT when I pull a section of my BIAB bag free from the rim of my pot and check the temp of the wort in the in-between space (i.e., in the space between the bag and the side of the pot), the temp will read a few degrees higher.
My questions are, 1) should I care about this temperature difference and 2) if so, which temperature is the one to care about (that of the wort inside the bag while it's in the kettle or that of the wort between the bag and the kettle wall)?
Post #2 made 14 years ago
I'm not sure what the experts are going to tel you GWY but this used to drive me nuts!I was able to regain what sanity I hve by giving the mash a stir before I take a reading.That seems to even things out.
AWOL
Post #3 made 14 years ago
GrainWaterYeast,
I brew in a keggel with a spigot (ball valve). I draw off a pitcher of wort and dump it in the center of my bag. I do this three or four times. I stir and bingo it's even. The pitcher I use is metal because the wort is drawn from the bottom of the keggel. It is really hot! This evens out the water grain temperatures quickly so I can hit my temps spot on. Actually I am lucky to be within two degrees!
I brew in a keggel with a spigot (ball valve). I draw off a pitcher of wort and dump it in the center of my bag. I do this three or four times. I stir and bingo it's even. The pitcher I use is metal because the wort is drawn from the bottom of the keggel. It is really hot! This evens out the water grain temperatures quickly so I can hit my temps spot on. Actually I am lucky to be within two degrees!
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tap 2 Bourbon Barrel Porter
tap 3 Czech Pilsner
tap 4 Triple IPA 11% ABV
Pipeline: Mulled Cider 10% ABV
http://cheesestradamus.com/ Brewers challenge!
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Post #4 made 14 years ago
I use a large potato masher to "mash" my grain (ie stir) before taking a reading, that way you get a uniform reading
Fermenting: -
Cubed: -
Stirplate: -
On Tap: NS Summer Ale III (WY1272), Landlord III (WY1469), Fighter's 70/- II (WY1272), Roast Porter (WY1028), Cider, Soda
Next: Munich Helles III
5/7/12
Cubed: -
Stirplate: -
On Tap: NS Summer Ale III (WY1272), Landlord III (WY1469), Fighter's 70/- II (WY1272), Roast Porter (WY1028), Cider, Soda
Next: Munich Helles III
5/7/12
Post #5 made 14 years ago
Hmm, I usually do a pretty good stir before taking readings, but the temp difference is still there (albeit lessened). I would love to be able to do what you do, BobBrews, and recirculate some of the wort from outside the bag into the bag, but I don't have a valve on my brew pot. Maybe I can look into getting my LHBS to install one (I'm not much of a handyman myself).
If, just for the sake of argument, this temp difference can't be eliminated, which temp would be the one to focus on the most? If I'm reading 65°C inside my bag but, say, 69-71°C outside the bag, does that mean that the beta-amylase activity has stopped for some/most/all of the grain? Aaaaaaaand, if that is the case, is it better then to shoot for a lower mash temp (60-64°C) in order to ensure that fermentables and unfermentables are both being produced (as would be the case if the mash was a uniform 65°C)?
Does this question even make any sense?
If, just for the sake of argument, this temp difference can't be eliminated, which temp would be the one to focus on the most? If I'm reading 65°C inside my bag but, say, 69-71°C outside the bag, does that mean that the beta-amylase activity has stopped for some/most/all of the grain? Aaaaaaaand, if that is the case, is it better then to shoot for a lower mash temp (60-64°C) in order to ensure that fermentables and unfermentables are both being produced (as would be the case if the mash was a uniform 65°C)?
Does this question even make any sense?
Post #6 made 14 years ago
Makes sense to me, only because I aim for a mash of 64°C.
And from what you have said above, it explains why my beers work so well with a low mash temp.
By the way, I only stir at the beginning and end of the 90 minute mash. The rest of the time everything just sits there doing it's thing.
And from what you have said above, it explains why my beers work so well with a low mash temp.
By the way, I only stir at the beginning and end of the 90 minute mash. The rest of the time everything just sits there doing it's thing.
"It's beer Jim, but not as we know it."
Post #7 made 14 years ago
Hashie - I know there's been a lot said on this forum and other brewing forums about mash times, and how the vast majority of the mash happens in the first 30 minutes or so. So perhaps if I'm more rigorous about getting my strike temperature correct (instead of saying, "Aw, I can just pop the burner on if it's a coupla degrees under"), I wouldn't be worrying about a temp difference because - by the time my mash tun/brew pot has lost enough degrees to warrant a burner kick - most of the conversion will be done anyhow so I can just leave it be until time for the mash out. Of course, the problem of inside the bag vs. outside the bag measurement comes back at mash out time, so...@#$%!
But, hey, the beers I make are still pretty damn good, so I must be doing something right!
But, hey, the beers I make are still pretty damn good, so I must be doing something right!
Post #8 made 14 years ago
If you are getting beer at the end of the day, that's all that really matters.
Another way to look at this, is the mash needs to be at x temperature, not the surrounding liquor. So long as the temp inside the bag, which is where it's all taking place, is at the right temp, I don't see a need for worry.
Another way to look at this, is the mash needs to be at x temperature, not the surrounding liquor. So long as the temp inside the bag, which is where it's all taking place, is at the right temp, I don't see a need for worry.
Last edited by hashie on 11 Jul 2011, 06:23, edited 5 times in total.
"It's beer Jim, but not as we know it."
Post #9 made 14 years ago
How do you even measure outside of the bag?
My bag pretty much lines my pot
Interestingly I thoroughly agitated my mash every 15 mins yesterday as it was 10C outside and I was losing 1C every 15 minutes so I was reheating every 15 mins
I got 93% efficiency!!!
Thinking back on my previous brews, the ones i agitated more often had better efficiencies
My bag pretty much lines my pot
Interestingly I thoroughly agitated my mash every 15 mins yesterday as it was 10C outside and I was losing 1C every 15 minutes so I was reheating every 15 mins
I got 93% efficiency!!!
Thinking back on my previous brews, the ones i agitated more often had better efficiencies
Fermenting: -
Cubed: -
Stirplate: -
On Tap: NS Summer Ale III (WY1272), Landlord III (WY1469), Fighter's 70/- II (WY1272), Roast Porter (WY1028), Cider, Soda
Next: Munich Helles III
5/7/12
Cubed: -
Stirplate: -
On Tap: NS Summer Ale III (WY1272), Landlord III (WY1469), Fighter's 70/- II (WY1272), Roast Porter (WY1028), Cider, Soda
Next: Munich Helles III
5/7/12
Post #10 made 14 years ago
Hashie - I see where you're coming from and can appreciate the logic. I guess my concern isn't so much is my beer going to turn out okay but, rather, am I hurting my efficiency? If the layer of grain closest to the wall of the bag is getting overheated by the water outside the bag, does that mean that those grains are all pooped out and not giving me the good stuff anymore? But - hey - even if it does mean a loss in efficiency, it can't be more than a couple of points.
Stux - I use a nylon mesh grain bag which is pretty fine, and when I pull a side of the bag free from the pot (like when taking the bag out...but you don't actually take it out) and measure the temp of the wort in the space created between the bag and the pot wall, it is always a few degrees higher than when I measure the temp in the center of the pot (where all the grain is). When you say you get better efficiencies from the brews you agitate more, this might be answering my question to Hashie above. In other words, lots of agitation means that your heat throughout the pot is more uniform.
Anyhow, I know this topic might seem overly anal retentive, but I think it's one of those areas where BIAB could be "challenged" by traditional batch spargers.
Stux - I use a nylon mesh grain bag which is pretty fine, and when I pull a side of the bag free from the pot (like when taking the bag out...but you don't actually take it out) and measure the temp of the wort in the space created between the bag and the pot wall, it is always a few degrees higher than when I measure the temp in the center of the pot (where all the grain is). When you say you get better efficiencies from the brews you agitate more, this might be answering my question to Hashie above. In other words, lots of agitation means that your heat throughout the pot is more uniform.
Anyhow, I know this topic might seem overly anal retentive, but I think it's one of those areas where BIAB could be "challenged" by traditional batch spargers.
