Troubleshooting mash temperature

Discussion in 'General Brewing Discussions' started by Sunfire96, Mar 28, 2021.

  1. Sunfire96

    Sunfire96 Well-Known Member

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    Hello all! One of the issues in my brewery is being unable to maintain a consistent mash temperature when I brew 2.5 gallon batches. I use a 5-gallon rubbermaid beverage cooler from The Depot wrapped in Reflectix insulation and when I mash there is a towel underneath and on top for insulation. And yet I lose about 3-4 degrees Fahrenheit within 20 minutes. Besides adding more insulation (Reflectix warns that doubling up insulation does not do much unless you leave an air gap between the layers), I had 2 ideas for a more consistent mash and would love some feedback from you all.

    1) Full volume mash: larger volume means larger thermal capacity and more likely to hold it's temp. Downsides: lowered efficiency (but not by much), and I wouldn't be able to add more water to increase the temp later on if it dips too low.

    2) Temperature step mash program: begin mash at 1.25-1.5 qts/lb of strike water, hold between 143-146F for 30 minutes, then add calculated amount of boiling water to increase to 153-156F for 30 minutes. Lauter, sparge, mashout as normal. Downsides: lower volume means lower thermal capacity, so my temps are pretty much guaranteed to drop in the first 20 minutes, and then again after the step up to the beta-amylase range.

    What would you do if you were me (using the equipment mentioned above)?
     
  2. Head First

    Head First Well-Known Member

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    Do you preheat the tun? If mash drops right away and not so much later then this could definitely help. Overheating water and waiting for some cool down would work just the same.
     
  3. Donoroto

    Donoroto Well-Known Member

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    Pre- heating was also my first thought.

    Do you have a pump? A poor man's RIMS can be made from tubing in a pot of hot water.
     
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  4. Bubba Wade

    Bubba Wade Well-Known Member

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    Before I got the electric system, I used that same 5-gallon Home Depot beverage cooler for a 2.5 gallon batch. I did not pre-heat. For a 150 degree mash, I would start with 3.25 gallons of 160 degree water. After stirring everything in well, the temp was around 152.

    Between heating the grains and the mash tun, I lost about 8 degrees of water temperature almost immediately. I would seal up the cooler and leave for an hour. At the end, I was in the 148-149 range.

    What’s the starting temperature of your mash water?
     
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  5. Sunfire96

    Sunfire96 Well-Known Member

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    Thanks for the replies all. Here is my current process for a 2.5 gallon batch:

    Heat strike water to about 175F, transfer through tubing to MLT. I lose about 5 degrees during the transfer. I let the water sit in the MLT until the water is about 165F, then I dough in and stir throughly. I usually lose between 9-11 degrees F after mashing in.

    Take the temp and a refractometer reading ,and stirring, every 15-20 minutes. Lately about halfway through the 60 minute mash I add 1-2 qts of boiling water to get back above 150F.
     
  6. Sunfire96

    Sunfire96 Well-Known Member

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    No pump :(
     
  7. Bubba Wade

    Bubba Wade Well-Known Member

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    Once you have the grain stirred in well and the dough balls eliminated, you might try just sealing up the mash tun for an hour. No stirring, no gravity readings. You lose a bit of heat every time the lid comes off. You can still use a temperature probe with a cable. The lid will thread right over the braided cable. Then if the temperature is too low , you can add a bit of boiling water.
     
  8. Hawkbox

    Hawkbox Well-Known Member

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    So my method (Which is kind of heresy) is to overheat the water for the amount of losses I expect from all the steps (Around 10C in the winter, 6C summer) and then I move my probe around until the heat matches what I want. Then I put the lid on and walk away for an hour.

    From what I can gather most of the conversion is done in the first 20 minutes or so anyway, so I don't know if I would stress super hard about this issue. Pre heating will help, but if you already factor it into your math it won't make a difference.

    You could see about a better cooler? My chest Coleman cooler loses around 1C per hour.
     
  9. Nosybear

    Nosybear Well-Known Member

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    Both would help but as long as you're using passive temperature control (read cooler), you're going to have temperature losses. Warming the tun won't help: As long as there's a temperature difference between the outside of the mash (the inner wall of the cooler) and the outer wall, you will lose heat. Adding reflectix to the outside doesn't help much - most of the heat will be lost to the air space above the mash and through the top - you're better off throwing a blanket over the lid! As to your step mash notion, if you're stirring the mash and hitting your initial temperature, you're accomplishing somewhat of the same thing due to temperature differences. Mash is too thick for much convection and it's not very conductive so the inside will stay at or near the desired temperature, the outside will cool.

    I've had similar problems if I use the 5-gallon cooler. I even had the same issues using the 10 gallon cooler before I started adding heat. It's a difficult problem to overcome: What you might do is to stir your mash, cover it, stir it after 10 minutes and add boiling water to bring the temperature back up, and so forth. At our scale a degree or two isn't going to create much of a difference.
     
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  10. Ozarks Mountain Brew

    Staff Member

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    Investigate mash infusion, that's what I use, in my case for my 12 gallon batch I add water 10 degrees above my target, now that's based on a lot of rules and there's a calculator here that will get you close
     
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  11. Trialben

    Trialben Well-Known Member

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    I'd try a full volume mash.
    I find when I do a double batch size on my brew rig the temp holds more stable the element does kick on as much.

    I'm with Hawkbox on the conversion it happens pretty quick.
     
  12. Sunfire96

    Sunfire96 Well-Known Member

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    Thanks everybody. I think full volume mash sounds like the way to go next time. I'll add another towel on top and leave the lid on like @Bubba Wade suggests (I should feel confident enough in my process now to know that I'm getting conversion without checking throughout the 60 min mash).

    Taking this another step: does anyone know of a food safe rigid foam insulation? I was thinking of cutting a piece to fit inside the MLT and then placing it on top of the mash. I suppose I could try Reflectix, but I want to make sure it's food safe.
     
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  13. Sunfire96

    Sunfire96 Well-Known Member

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    I'm not sure what you mean by that, could you please explain it more?
     
  14. 56 Firedome

    56 Firedome Active Member

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    #14 56 Firedome, Mar 30, 2021
    Last edited: Mar 30, 2021
    I use an Igloo 10 gal drink cooler. It was obvious that the lid was hollow & uninsulated. Heat loss at 152 F was substantial. I used "Great Stuff" foam sealant & a 3/8" bit. The foam is a closed cell low expansion type. I drilled holes in the lid around the outside lip , from the inside, & in the middle strategically placed to allow the foam to fill the void. It worked great. I used Silicone Sealer to close the holes. I don't think the Great Stuff is Food Grade but it is all inside the lid & not exposed to the Mash. I don't think the foam filled lid is as well insulated as the sides of the Igloo but I can hold 170 F for an hour losing only 2 deg F.
    I have used the 1" thick Blue Foam board (Lowes/Home Depot) on the top of my Sparge Tank, a 3 gal drink cooler because I have been using a Sous Vide to heat & hold 170 F Sparge water. I didn't want to cut up the lid, foam insulated, so I made a lid from the Blue Foam with a cut out for the SV.
    Is this safe? I've been using the 10 gal Igloo for 6 years & the 3 gal Igloo for 4 years with no issues & I'm still alive & well, far as I know anyway.
     
  15. Trialben

    Trialben Well-Known Member

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    I used to use alfoil on top of my mash I dont Any more (last couple of brews. Foam would work too but I wouldn't want it touching the hot mash just incase any flavour infusion :rolleyes:
     
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  16. Craigerrr

    Craigerrr Well-Known Member

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    A couple of years ago I had this cooler, bought it used for $10. Temperature drop over an hour was 1C.
    IMG_20181207_1821181.jpg
     
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  17. Nosybear

    Nosybear Well-Known Member

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    I know you. You are not well.... :D:D:D:D
     
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  18. Nosybear

    Nosybear Well-Known Member

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    p.s. Fill the lid as Bob suggests, then add additional information on top. No need to worry about food-grade in that case....
     
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  19. Donoroto

    Donoroto Well-Known Member

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    Maybe not. There are quite a few web sites stating that polystyrene foam can leach styrene (which is toxic) into whatever it touches, particularly at high temperatures. Whether that's true or not is debatable.

    Adding some kind of impermeable barrier between the blue foam and the water can eliminate any risk. Think aluminum foil adhered to the foam for example.
     
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  20. 56 Firedome

    56 Firedome Active Member

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    The blue foam is only on the Sparge tank lid but I like the al foil on the bottom of the foam lid if for no other reason than the reflective nature of the foil. I've that a try.
     
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