Lost 6 degrees in 1 hour mash

First AG batch is finished and I ended up losing 6 or 7 degrees in an hour mash. I wasnt expecting this much of a loss seeing that my MLT is a cooler. Is this typical? Will this have any negative effects on my final product?

While I've only got a handful of brews under my belt, I had the same problem when I first started. All I did to fix this was set the MLT cooler on top of a chair (or milk crate) to get it off the ground. I wish I could offer more as far as the logistics and science behind this, but all I really know is it has to do with the heat distribution from the cooler to the ground. Getting it up off the floor helps eliminate this. Hope this helps/works for you.

Did you preheat it first with hot tap water? That makes a huge difference. It also will lose heat more rapidly if it's less than 2/3 full.

Try this. It's a piece of 2 inch foam insulation. My last mash lost 3 tenths in one hour.

As stated, pre-heating helps vastly, and if you are setting it on the concrete it will suck out some of the heat, so keep it off the ground.

Also, how often did you open it? I generally only do 1-2 stirs during my entire mash...I don't want to lose too much heat and the last two runs I had 92% efficiency.

You can also wrap it in towels and stick a pillow on top of it. More insulation is never a bad thing.

Lastly, be sure your temp was correct to begin with. Use an accurate mash calculator like Green Bay Rackers--Mash Calculators so you get it right the first time and don't have to mess with it.

Throw your thermometer in and give it time to sit at least 10 minutes for the heat to distribute before you check, or you will get an inaccurate reading. Then you'll see what the actual temp of the mash is. You may find that it didn't drop that much after all.

In any case, don't worry about it. I've never had a bad beer from mashing too low. What was your starting and finishing temp for your mash, anyway?

That... is... awesome.

I was trying to think of something like that the other day, but I only got as far as a few layers of tin foil on the surface of the grain before putting the lid on.

Evets said:

Try this. It's a piece of 2 inch foam insulation. My last mash lost 3 tenths in one hour.

Click to expand...

That is pretty slick. I'm getting ready to try my first AG brew soon with a newly fabricated MLT. Now that I have seen this, I'm gonna have to go look around and see where I might find a piece of foam large enough to work with my cooler.... That would solve any dead space issues that might come up due to the size of the mash vs the size of the cooler.... great post...

PS- what type of foam is that? Is it styrofoam or some sort of foam rubber?

1st ag batch left MLT sittin on the floor all alone and lost 6 deg in one hour. since then weve been sitting it on a pillow and wrapping it with a sleeping bag and havent lost more than one degree. We pre-heat with almost but not quite boiling water for 15-20 minutes.

1st ag batch (Bee Cave Haus pale ale) tasted amazing anyway

Pretty slick Evets:
Cudos on the foam cap. I have been planning to do that soon as well as I lose about 5 degrees in an hour. I tried keeping it off the ground, but it is way obvious the problem is the lid as I can feel how warm the lid is during the mash. If the top of the lid is warm, it is letting out heat. It's either underinsulated, or not insulated at all.

I am a bit worried about what most foam might leach under heat, so was going to go with standard styrofoam like cut the bottom off a disposable cooler. What did you use?

Another idea floating around here is to drill some holes in the lid of your MLT and squirt some great stuff in there. Considering of course, that your lid is hollow.

I wrap mine in a big sleeping bag. Keeps the temp within a degree for the whole hour.

I always allow about 25-30 degs leeway for my strike temp just to make sure my cooler is maxed on heat absorption. The first 10-15 degs is for the cooler to heat up to max and the second 10-15 degs is to acct for the heat loss due to the room temp grain addition. Remember....it is alot easier to cool down a mash then to heat is back up again (with a cooler tun).

The round coolers normally used for drinking water are not air tight - they can't be, because they have to let air in around the lid to prevent a vacuum when water is drained out at the bottom. This is not a problem when the cooler is full of cold water, because air cooled by the water will tend to sink, not rise. Of course, when using a cooler as a MLT, this ventilation around the lid allows hot air to escape. Reducing the headspace above the mash greatly reduces the amount of heat escaping. You don't even have to have the foam in direct contact with your mash, as long as you can minimize the headspace and prevent hot air from escaping (it doesn't have to be totally air tight). One thing I do, which I haven't seen mentioned is to wrap my ball valve with a towel to prevent heat being conducted out through the brass. And +1 for preheating the cooler, and starting with the strike water hotter than you think you need it.

I had a problem last night when doing a 1/2 batch. Normally I might lose 1-2 degrees over the hour, but last night I lost a bunch more. I think it had to do with headspace more than anything. I would consider getting a smaller MLT for batches that small in the future.

I thought I was really smart when I thought up my mashing technique, but really I stole it from Dave Lines book, Brewing Beers Like the Ones You Buy.

Tried it once. I mashed in the kettle and lauter & sparge in a Papazian bucket in a bucket setup.

I filled the sink with 66 deg C water, plonked the stockpot in the sink, and covered it with a blanket. 1 and half hours, the mash lost 1 degree, and I think that was because I the sink water wasn't quite 66 deg. I made a mistake (I do that sometimes).

I live in central Texas. Down here we have to put an ice pack on top of the cooler to keep it from rising a few degrees. Man, it's hot!

KopyKat said:

I live in central Texas. Down here we have to put an ice pack on top of the cooler to keep it from rising a few degrees. Man, it's hot!

Click to expand...

That works pretty well in the winter, but what do you do in the summer?

KopyKat said:

I live in central Texas. Down here we have to put an ice pack on top of the cooler to keep it from rising a few degrees. Man, it's hot!

Click to expand...

Yep! My comment was going to be the OP should move to Texas!

I brewed on May 23rd and actually GAINED temperature in my MLT! (it was a +90F day in direct sunlight around 2PM)

My first AG batch in the Home Depot cooler held temp for an hour. Only things we did were to set it on a table, and fill the lid with Great Stuff. Just drill a few holes, and use the nozzle to spray it inside. Wait for it to dry, and scrape it off the top, and you're good to go!

I haven't found any scrap pieces of thick foam yet (read: too cheap to buy a full sheet at HD) but I did take a large ziplock and filled it with some packing peanuts. Put that on top of the mash inside the cooler. Kept the loss to 1 deg over 60 min.
Jason

jwright said:

I haven't found any scrap pieces of thick foam yet (read: too cheap to buy a full sheet at HD) but I did take a large ziplock and filled it with some packing peanuts. Put that on top of the mash inside the cooler. Kept the loss to 1 deg over 60 min.
Jason

Click to expand...

I might try that myself. I have a couple boxes full of the peanuts but no scraps of thick foam rubber or styrofoam. I might try it using a trash bag and see how it goes...

I swear by the Coleman Extreme coolers. They really live up to their name. I do not know what the size variations are but I have the 70qt model and I do anywhere from low to moderately high gravity brews and it has no issues holding temps. I let it soak over night with oxyclean and hot tap water and it was still hot the next morning

Coleman Extreme 52 qt here. I love that thing. No heat loss and it might not even gain heat in TX.

I lost about the same amount of heat in my first AG batch...

Reason - if you are anything like me, I was so excited that I opened the cooler way too much to stir and check the temp and to just look around!! Next time once I hit my temp, its going to stay closed the entire time and Im expecting much better results!

When I used to have a hot tub, it came with a thin layer of dense bubblewrap. The idea was to keep water vapor from forming, as the vapor always comes from the hottest molecules.
I've been using the plastic grain bags from the LHBS to prevent steam from forming, and you can see the difference immediately. That said, I just into some faced insulation, and I'll be cutting out a foam insert soon.

I wonder if something as simple as a towel in a gallon sized ziplock would work for the round coolers like mine.

I'm using a Coleman Xtreme cooler for a MLT and a Igloo 10 gal. for sparge water. The insulation on the Igloo is quite thin compared to the Coleman. If you want to cut down on heat loss you might try insulating your shut-off valve. I just wrap a towel around the shut-off while mashing and it seems to help a lot.

Evets said:

Try this. It's a piece of 2 inch foam insulation. My last mash lost 3 tenths in one hour.

Click to expand...

+1 on that idea. I use the same thing, and have a similar loss of heat during the mash.

You guys talking bout the blue or pink foam?

drayman86 said:

+1 on that idea. I use the same thing, and have a similar loss of heat during the mash.

Click to expand...

Bringing up a thread from z’dead.

Does anybody know of any legitimate concerns with foam insulation being in contact with the mash? Particularly if little particles happen to break off and later get stirred deeper into the mash during a batch sparge infusion?

Also, is it preferable to remove the thin plastic cover or leave it on the side contacting the mash?

I like this idea a lot. Particularly b/c I'm thinking of upgrading my damaged 36 qt Coleman Xtreme to a new 62 qt version of the model. [The idea being to take another shot at converting it without damaging it, to be able to brew bigger beers, and to be able to dabble in 10 gallon batches at somepoint as well. But considering that I'll still be doing 5 gal batches of medium strength beers more often than not, I anticipate a lot of open head space in the MLT and this seems like the perfect solution to heat loss problems resulting from that.]

But is it safe?

Perpetuating the topic.

Judochop said:

Bringing up a thread from z’dead.

Does anybody know of any legitimate concerns with foam insulation being in contact with the mash? Particularly if little particles happen to break off and later get stirred deeper into the mash during a batch sparge infusion?

Also, is it preferable to remove the thin plastic cover or leave it on the side contacting the mash?

I like this idea a lot. Particularly b/c I'm thinking of upgrading my damaged 36 qt Coleman Xtreme to a new 62 qt version of the model. [The idea being to take another shot at converting it without damaging it, to be able to brew bigger beers, and to be able to dabble in 10 gallon batches at somepoint as well. But considering that I'll still be doing 5 gal batches of medium strength beers more often than not, I anticipate a lot of open head space in the MLT and this seems like the perfect solution to heat loss problems resulting from that.]

But is it safe?

Click to expand...