Kettle Insulation/Acceptable Temperature Drop in Mash

[Epos7]

Over the colder months, and even in warmer weather, I find one of the most challenging aspects of BIAB is maintaining a good mash temp. I wrap my kettle in a sleeping bag, but even then it's not uncommon for the mash temperature to drop by 6 degrees or more over 60 minutes. I've had good success refiring the burner every 15 minutes, but the constant attention required can make the whole process feel a little frantic. I've also tried wrapping my kettle in reflectix as well as the sleeping bag. The reflectix did help, but sometimes it doesn't do enough, and it has to be removed before you start the burner again or it will melt. I try to minimize opening the lid as much as possible during the mash, but when I've tried going the whole mash while keeping the kettle wrapped the whole time, I still lost more heat than I was comfortable with.

A few questions for my fellow BIAB'ers:

1) How much heat loss during mash are you comfortable with? Are you comfortable with more heat loss on higher mash temps?

2) How do you insulate your kettle?

3) Does anyone shoot for a higher mash temp to compensate for the extra heat loss in BIAB as compared to a system with an insulated mash tun?

 

[rhys333]

I had the same problem, and I really don't like having to fire up the burner every few minutes to maintain temp as I'm concerned about temp differential between the bottom and top. My solution is to mash indoors, in my old 5 gallon pot, instead of outdoors in the 10 gallon kettle. I barely lose a degree in temp that way and I know its stable throughout the mash. I just use about 3 gallons for mashing and reserve another 4 in the BK. Quick transfer at 60 minutes for a dunk sparge and jobs a good'ne.

 

[FoCobrewguy]

I have a similar problem, I think my last batch definitely missed my SG because of the heat drop. I just use reflectix wrapped like 3 times around the kettle and a snowboard jacket on the top. I went to a brew demo at my LHBS and he said on his home set up he recirculates for the mash and will check the temp through a temp probe during the recirculation. If he sees the temp drop he turns on the burner. With the recirculation he said he does not have scorching issues and don't have to worry about differences in the top or bottom. Just a thought, I plan to incorporate it into the next brew day or so just trying to figure out where to return into the kettle from.

 

[RM-MN]

When you do a BIAB batch the fact that you use a mesh bag allows you to mill the grains fine. If you do that you can ignore the temperature drop over the 60 minutes because the conversion will be done long before the hour is up. The main reason for the 60 minute mash is a compromise that is necessary for a conventional mash tun where the grains cannot be milled so fine because it will cause a stuck mash. With the larger particle size it takes longer to gelatinize the starch which is the major factor in the longer mash.

If you want to know how long you need to mash, get a bottle of iodine from the pharmacy. Take a white plate or other white surface and place several drops of iodine on it separated by a bit of space. As soon as you mix the grain into the water to start your mash, take a sample of the wort with a little grain in it and place a drop of it next to a drop of iodine and then mix them. The iodine/wort should be blue, signifying that there is starch present. Take another sample at 5 minutes and repeat the test and do that for each 5 minutes until the iodine does not change color. At that point your mash is done with conversion. Don't quit just yet, you still need time to extract color and flavors and that takes a bit longer than conversion. I usually let my mash go for 20 to 30 minutes because my grains are milled very fine.

 

[Murphys_Law]

I wrap my kettle in reflectix or what ever that crap is called and usually just get a few degrees an hour. I also use a 10G kettle that is near full so that helps with heat retention.

View attachment ImageUploadedByHome Brew1488588011.071696.jpg

 

[PADave]

I use an old winter jacket and only loose 2-3 degrees over an hour. Head space has a lot to do with it. With a 10 gallon kettle, full volume mash, there is not much air space in there. But like RM-MN said above, conversion happens pretty quickly, so I don't worry too much about how much the temp drops.

 

[bfish]

12.5 gallon kettle here, I just but a hoodie around the pot, and throw an extra blanket on the lid (IMO where most of the heat loss occurs). I start with the temperature that priceless calculator gives me for the strike water which is based on my desired mash temp. I do quickly stirring to break up any clumps then put on the hooded sweatshirt and lay the blanket on top (I don't even bother to unfold it). After 60 minutes, I am usually only a few degrees (about 2-6) below targeted mash temp (even on windy 40 degree days). Reread RM-MN post above, he gives good advice as to why. I also double crush on my cereal killer (set at credit card width).

 

[radwizard]

I use that reflex tape and wrap a down jacket over the top. The reflex stuff is triple wrapped and goes under, around, and over it. I use the jacket as over kill, just in case I have a space in the insulation. I lost about 1 degree in an hour when the temp dropped below freezing this winter.

 

[Epos7]

When you do a BIAB batch the fact that you use a mesh bag allows you to mill the grains fine. If you do that you can ignore the temperature drop over the 60 minutes because the conversion will be done long before the hour is up. The main reason for the 60 minute mash is a compromise that is necessary for a conventional mash tun where the grains cannot be milled so fine because it will cause a stuck mash. With the larger particle size it takes longer to gelatinize the starch which is the major factor in the longer mash.

If you want to know how long you need to mash, get a bottle of iodine from the pharmacy. Take a white plate or other white surface and place several drops of iodine on it separated by a bit of space. As soon as you mix the grain into the water to start your mash, take a sample of the wort with a little grain in it and place a drop of it next to a drop of iodine and then mix them. The iodine/wort should be blue, signifying that there is starch present. Take another sample at 5 minutes and repeat the test and do that for each 5 minutes until the iodine does not change color. At that point your mash is done with conversion. Don't quit just yet, you still need time to extract color and flavors and that takes a bit longer than conversion. I usually let my mash go for 20 to 30 minutes because my grains are milled very fine.

I've heard a lot of people say this who know a lot more than me, but it doesn't match up with my observations. I'm milling my grain pretty fine with a mill gap set to 0.020" and I typically take a gravity reading every 15 minutes during the mash, making sure I'm stirring well before taking the sample. My conversion process is always ongoing over the whole 60 minutes, often with an increase in gravity after I squeeze the bag. I do get pretty good conversion so long as I stir a lot, but it does seem to take the full 60 minutes.

I haven't tried the iodine test yet. Maybe I will try that next batch I brew to see if it confirms my gravity readings.

 

[Epos7]

I have a similar problem, I think my last batch definitely missed my SG because of the heat drop. I just use reflectix wrapped like 3 times around the kettle and a snowboard jacket on the top. I went to a brew demo at my LHBS and he said on his home set up he recirculates for the mash and will check the temp through a temp probe during the recirculation. If he sees the temp drop he turns on the burner. With the recirculation he said he does not have scorching issues and don't have to worry about differences in the top or bottom. Just a thought, I plan to incorporate it into the next brew day or so just trying to figure out where to return into the kettle from.

I think recirculating is the best approach, probably with an electric setup. I'd like to get there eventually but for now I'm trying to make it work without recirculating. Good luck with your attempt, let us know how it goes

 

[Epos7]

I wrap my kettle in reflectix or what ever that crap is called and usually just get a few degrees an hour. I also use a 10G kettle that is near full so that helps with heat retention.

I've been brewing 5 gallon batches in a 15 gallon kettle, so all the head space in there could be contributing to the extra heat loss. For my next batch I plan to try brewing a 10 gallon batch, partially to see how much better I can maintain my temps during mash.

 

[PADave]

I've heard a lot of people say this who know a lot more than me, but it doesn't match up with my observations. I'm milling my grain pretty fine with a mill gap set to 0.020" and I typically take a gravity reading every 15 minutes during the mash, making sure I'm stirring well before taking the sample. My conversion process is always ongoing over the whole 60 minutes, often with an increase in gravity after I squeeze the bag. I do get pretty good conversion so long as I stir a lot, but it does seem to take the full 60 minutes.

I haven't tried the iodine test yet. Maybe I will try that next batch I brew to see if it confirms my gravity readings.

That's your problem right there, taking the lid off too much! I give mine a one stir with about 15 minutes left.

 

[wilserbrewer]

I would suggest bumping your mash temp up a bit if brewing outside in the cold weather.

Don't try and hit a 149 strike temp....bang head lol

I'm with RM-MN on this, with a good crush and hitting strike temp plus a few degrees if it's cold out, I can't imagine not getting good conversion.

 

[Chris_Primavera]

A few questions for my fellow BIAB'ers:

1) How much heat loss during mash are you comfortable with? Are you comfortable with more heat loss on higher mash temps?

3°F/90 min - no

2) How do you insulate your kettle?

Quilt secured with bungee cords at the bottom. Burner base wrapped 80% around with aluminum foil <- *Important*

3) Does anyone shoot for a higher mash temp to compensate for the extra heat loss in BIAB as compared to a system with an insulated mash tun?

No - I usually mash at 149°-151°F for 90 minutes and mash out to 165°F
I stir at 30 minutes (-0°F) and 60 minutes (-1°2°F). My mash volume is about 12 gallons. At 90 minutes I am usually down 2° -3°F. The initial 30 minutes probably converts 90% of the starches so I make sure my mash-in temp is spot on.

 

[thekraken]

When you do a BIAB batch the fact that you use a mesh bag allows you to mill the grains fine. If you do that you can ignore the temperature drop over the 60 minutes because the conversion will be done long before the hour is up. The main reason for the 60 minute mash is a compromise that is necessary for a conventional mash tun where the grains cannot be milled so fine because it will cause a stuck mash. With the larger particle size it takes longer to gelatinize the starch which is the major factor in the longer mash.

If you want to know how long you need to mash, get a bottle of iodine from the pharmacy. Take a white plate or other white surface and place several drops of iodine on it separated by a bit of space. As soon as you mix the grain into the water to start your mash, take a sample of the wort with a little grain in it and place a drop of it next to a drop of iodine and then mix them. The iodine/wort should be blue, signifying that there is starch present. Take another sample at 5 minutes and repeat the test and do that for each 5 minutes until the iodine does not change color. At that point your mash is done with conversion. Don't quit just yet, you still need time to extract color and flavors and that takes a bit longer than conversion. I usually let my mash go for 20 to 30 minutes because my grains are milled very fine.

Do you know what the micron is, or the material of your bag? What about the gap on your mill, and or your milling procedure?

 

[Murphys_Law]

I've been brewing 5 gallon batches in a 15 gallon kettle, so all the head space in there could be contributing to the extra heat loss. For my next batch I plan to try brewing a 10 gallon batch, partially to see how much better I can maintain my temps during mash.

Head space will certainly lead to greater temp loss. Air changes temperature very quickly while water will keep its thermal load much longer (i.e. slower temp drops).

 

[RM-MN]

Do you know what the micron is, or the material of your bag? What about the gap on your mill, and or your milling procedure?

The bag I use is a paint strainer bag and I don't have the size of the opening of the mesh, The mill is a Corona style like this one. http://www.discounttommy.com/p-189-...er-for-wheat-grains-or-use-as-a-nut-mill.aspx

I have it set as tight as I can. When empty the plates that do the grinding are rubbing. The grain comes out looking like this.

 

[Epos7]

That's your problem right there, taking the lid off too much! I give mine a one stir with about 15 minutes left.

That was my thought too! However I find that if I'm not stirring every 15 minutes and refiring the burner to bring the mash back up to temp, my conversion efficiency drops into the mid 80's. When I'm stirring at 15 minute intervals my conversion efficiency is in the mid 90's.

On a batch I brewed 2/20, I left the mash alone for 60 minutes and just stirred well at the beginning and end. My target mash temp was 150F, after mashing in and stirring I was at 151F, and after a 60 minute mash I was down to 146F. Conversion efficiency was only 86% though ipe:

Could be that I just need to keep narrowing the gap on my mill. I think I'll try that next, maybe drop down to 0.015" and see if I can achieve good conversion efficiency while leaving the mash alone to avoid heat loss.

 

[Epos7]

Burner base wrapped 80% around with aluminum foil <- *Important*

Haven't heard of this before, you've given me something to try!

 

[wilserbrewer]

That was my thought too! However I find that if I'm not stirring every 15 minutes and refiring the burner to bring the mash back up to temp, my conversion efficiency drops into the mid 80's. When I'm stirring at 15 minute intervals my conversion efficiency is in the mid 90's.



On a batch I brewed 2/20, I left the mash alone for 60 minutes and just stirred well at the beginning and end. My target mash temp was 150F, after mashing in and stirring I was at 151F, and after a 60 minute mash I was down to 146F. Conversion efficiency was only 86% though ipe:



Could be that I just need to keep narrowing the gap on my mill. I think I'll try that next, maybe drop down to 0.015" and see if I can achieve good conversion efficiency while leaving the mash alone to avoid heat loss.

When you dough in, do you take the temperature immediately? I feel it may take some time, say 3-5 minutes for the temp to stabilize and the grain and strike water to reach equilibrium.

I have a hunch that if one doughs in quickly and takes a temp, a false high reading may be obtained as the grain is still absorbing heat.

Just a hunch I have that it takes more time and more stirring to reach equilibrium than one may intuitively think.

Maybe starting the mash at 151 is a couple few degrees too low, idk. Would starting the mash at 153 -154 alter the attenuation significantly or at all?

 

[madscientist451]

I grew weary of the temperature swings and got a cooler and put my BIAB in that.
Problem solved. Its another thing to buy and clean, but I don't have any spilled wort from pulling the bag out. With a cooler I can also do re-circulation, step mashes and batch or fly sparging if I want to. So it really opened a lot of options for me.
But another way to raise the temperature of the mash is to have a side pot with boiling water ready.
Check the temp every 20 minutes, then add the correct amount of boiling water to bring the temperature up. You don't have to take the insulation off, but taking the lid off and stirring in the boiling water causes heat loss, so you are chasing a moving target.
Use the rest calculator on the Green Bay Rackers web site to determine how much boiling water to add, seems to work pretty good.
Many brewers just don't worry about it and the beer comes out fine.

 

[Epos7]

When you dough in, do you take the temperature immediately? I feel it may take some time, say 3-5 minutes for the temp to stabilize and the grain and strike water to reach equilibrium.

I think it does; I usually stir for 2-3 minutes before I hit or get close to my mash temp.

As far as a higher mash temp altering the attenuation, I'm wondering if it depends on how quickly the conversion process completes. For those whose conversion finishes in 15-20 minutes, it may produce a less dry beer? For me, conversion takes the full 60 minutes, so my theory is the higher temp at the beginning could be balanced out by the lower temp at the end.

 

[thekraken]

I think it does; I usually stir for 2-3 minutes before I hit or get close to my mash temp.

As far as a higher mash temp altering the attenuation, I'm wondering if it depends on how quickly the conversion process completes. For those whose conversion finishes in 15-20 minutes, it may produce a less dry beer? For me, conversion takes the full 60 minutes, so my theory is the higher temp at the beginning could be balanced out by the lower temp at the end.

You stir for three minutes? Maybe that's part of your problem?

 

[Epos7]

You stir for three minutes? Maybe that's part of your problem?

I have to in order to get good conversion. I'm going to try a finer crush for my next batch to see if I can stir less and still achieve good conversion efficiency.

 

[jwalk4]

A lot of guys still preheat their MTs maybe you can try something similar with your sleeping bags, towels, and coats.

Heat your strike water 5 to 10 degrees above your desired temp, then cut your heat and wrap it up. When your water falls to 161- 158F, then add your grain and see how it holds temp.

 

[mongoose33]

I've been brewing 5 gallon batches in a 15 gallon kettle, so all the head space in there could be contributing to the extra heat loss. For my next batch I plan to try brewing a 10 gallon batch, partially to see how much better I can maintain my temps during mash.

One solution to this is to take a 1" thick piece of foam insulation, cut it to a circle just shy of the diameter of the kettle, and float that on top of the mash. It'll cut way down on the headspace losses.

 

[thekraken]

Do you wrap it in foil or plastic wrap or anything?

 

[jonny24]

One solution to this is to take a 1" thick piece of foam insulation, cut it to a circle just shy of the diameter of the kettle, and float that on top of the mash. It'll cut way down on the headspace losses.

Do you wrap it in foil or plastic wrap or anything?

I've been thinking about an insulation disc- I'm looking at switching to BIAB and researching mash tun insulation. I was thinking about a plastic wrap to keep the foam away from the mash, but I'm not sure if the temps or times involved are enough to worry about chemical leaching?

My other thought was to make the disc large enough that it actually is tight against the sides, so that you can leave it slightly above the surface.

 

[wilserbrewer]

Well, couple options that I know of....

1. Rdwhahb
2. Rather than an insulated disc, just use a round shape of aluminum foil shaped to fit the tun and floated on top of the mash.

Option 1 is easier and may be just as effective

 

[BufferNuggets]

I do not know if this is plausible with you set up, but, I use my oven. I preheat it to the WM setting (~170F) and after I rain in the grain and stir I toss the whole kettle into the empty oven. I use a oven thermometer made to be in >375F and toss that into the middle of the grain to keep an eye on mash temp. I can leave that in the over for normally 60-90 mins without having to worry. I have even used it for a type of step mashing, tossing it in ~145F and letting the oven slowly raise the temp over 90 mins to 165F to mash out.

 

[Epos7]

I brewed a 10 gallon batch yesterday. I made a cap for my lid out of Reflectix, and used two sleeping bags instead of one. I also threw a couple sheets of tin foil on top of the burner in a half baked attempt to stop heat loss there.

It took five minutes of stirring after dough in to break up all the dough balls, and which point my mash temperature was 154.5F. I wrapped everything up and checked back in at the 30 minute mark, 25 minutes after I had put all my insulation on. Gave it a good quick stir to make sure the heat was distributed evenly, and my temp was 152.5F. I decided to refire the burner, brought it back up to just over 154F, and wrapped it back up again. At the end of the mash I was down to 152.5F again.

So with a 10 gallon batch and extra insulation, I was losing about 2.5F every 25-30 minutes. That's a lot better than my 5 gallon batches, but still required me to fire up the burner once during the mash.

I like the idea of pre-heating the sleeping bags, I'm just not sure how I would do it.

 

[RM-MN]

I brewed a 10 gallon batch yesterday. I made a cap for my lid out of Reflectix, and used two sleeping bags instead of one. I also threw a couple sheets of tin foil on top of the burner in a half baked attempt to stop heat loss there.

It took five minutes of stirring after dough in to break up all the dough balls, and which point my mash temperature was 154.5F. I wrapped everything up and checked back in at the 30 minute mark, 25 minutes after I had put all my insulation on. Gave it a good quick stir to make sure the heat was distributed evenly, and my temp was 152.5F. I decided to refire the burner, brought it back up to just over 154F, and wrapped it back up again. At the end of the mash I was down to 152.5F again.

So with a 10 gallon batch and extra insulation, I was losing about 2.5F every 25-30 minutes. That's a lot better than my 5 gallon batches, but still required me to fire up the burner once during the mash.

I like the idea of pre-heating the sleeping bags, I'm just not sure how I would do it.

Not if conversion was complete at 25 minutes. Did you check?

 

[Epos7]

Not if conversion was complete at 25 minutes. Did you check?

It was most of the way there. I hit 14.1 brix (1.057 SG) at the 30 minute mark, and ended up at 15.3 (1.062 SG) by the end of the mash.

 

[jwalk4]

I like the idea of pre-heating the sleeping bags, I'm just not sure how I would do it.

Probably would require you to lift/move your kettle, which some might find dangerous. But I would put down some wood or brick at the bottom of an old sleeping bag, then heat up all your water. Once youre 5-10 degrees higher than your strike temp, move the kettle onto the bricks and pull the sleeping bag up around it.

 

[JDXX1971]

I have been trying to control temps by wrapping jackets around the kettle and also firing the burner occasionally. I can keep it pretty close if I am attentive and pay attention but its sucks the fun out of it. I live near the coast and our property is heavily effected by coastal breezes. I believe that to be a big issue for some of us in particular areas. Now for me the real concern is the ability to create the same beers time after time as close as I can get them. I figure with the differences that are attainable by brewing a particular beer at different temperatures gives me some reason to be concerned with my mash temps???

But whatever, you know, I am going with a RIMS tube so I can Rdwhahb. Different strokes for different folks!!

 

[pricelessbrewing]

I've heard a lot of people say this who know a lot more than me, but it doesn't match up with my observations. I'm milling my grain pretty fine with a mill gap set to 0.020" and I typically take a gravity reading every 15 minutes during the mash, making sure I'm stirring well before taking the sample. My conversion process is always ongoing over the whole 60 minutes, often with an increase in gravity after I squeeze the bag. I do get pretty good conversion so long as I stir a lot, but it does seem to take the full 60 minutes.

I haven't tried the iodine test yet. Maybe I will try that next batch I brew to see if it confirms my gravity readings.

I will recommend checking your mash pH, and using bru'n water if you're not already. Adequate mash conditions should give maximum gravity by 50 minutes at the latest. Crush, dough in, and mash pH

 

[Epos7]

I will recommend checking your mash pH, and using bru'n water if you're not already. Adequate mash conditions should give maximum gravity by 50 minutes at the latest. Crush, dough in, and mash pH

I have been checking my mash pH and it is right where it should be. For the batch I brewed a couple days ago, I lowered my mill gap even further to 0.015" and my conversion efficiency shot up to over 97%. Conversion did appear to proceed faster as well, with it being mostly finished after 30 minutes

 

[Kee]

I grew weary of the temperature swings and got a cooler and put my BIAB in that.
Problem solved. Its another thing to buy and clean, but I don't have any spilled wort from pulling the bag out.

I bought a cooler last week and that's my plan.

 

[wilserbrewer]

I grew weary of the temperature swings and got a cooler and put my BIAB in that.

Problem solved. Its another thing to buy and clean, but I don't have any spilled wort from pulling the bag out. With a cooler I can also do re-circulation, step mashes and batch or fly sparging if I want to. So it really opened a lot of options for me.

But another way to raise the temperature of the mash is to have a side pot with boiling water ready.

Check the temp every 20 minutes, then add the correct amount of boiling water to bring the temperature up. You don't have to take the insulation off, but taking the lid off and stirring in the boiling water causes heat loss, so you are chasing a moving target.

Use the rest calculator on the Green Bay Rackers web site to determine how much boiling water to add, seems to work pretty good.

Many brewers just don't worry about it and the beer comes out fine.

Has there been an appreciable change in the beer now that you are not weary over mash temp?

I'm just not convinced it all that critical w
Modern highly modified malt.

Some feel yeast selection far influences
Attenuation more than mash temp.

 

[Kee]

Has there been an appreciable change in the beer now that you are not weary over mash temp?

I'm just not convinced it all that critical w
Modern highly modified malt.

Some feel yeast selection far influences
Attenuation more than mash temp.

I am also skeptical that a few degrees in mash temperature makes much difference. Still, I'm going to try the cooler method just because I'm used to using a cooler mash tun and believe the transition to BIAB will be more comfortable for me that way.