Creative Ideas For Maintaining Mash Temperature

Discussion in 'Homebrewing' started by OldBrewer, Nov 29, 2019.

  1. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    I use a 10 gallon Rubbermaid cooler mash tun for mashing five gallon batches, and I've had it for a very long time. I'm not sure whether the insulation is wearing out, or there is some other factor, but it no longer seems to hold heat as efficiently as it used to. The temperature can drop as much as 7 or 8 F over 1-1/4 - 1-1/2 hours of mashing. I keep the mash tun tightly wrapped with blankets during the mash. I also pre-heat the mash tun.

    I'm interested to know if others have creative ideas for maintaining a more steady temperature while using a 10 gallon cooler mash tun?
    #1 OldBrewer, Nov 29, 2019
    Last edited: Nov 29, 2019
  2. PortLargo

    PortLargo Devotee (465) Oct 19, 2012 Florida

    Not especially creative, but I add hot water. I have the same mash tun you describe and it loses about 1° every 15 minutes (always has). So I have some standby boiling water that is added during every stir cycle. I typically do a mash out (168) and let it rest 10 minutes. During sparge the runoff is typically down to low-mid 160s and I compensate by adding 180'ish sparge water. Fight fire with fire.
  3. billandsuz

    billandsuz Devotee (411) Sep 1, 2004 New York

    I think you are doing it right. Check for air leaks. There is no reason for the insulation to wear out. You may have managed to get water inside the air gap, between the cooler walls. That would wick heat like an MFer. The air gap is plenty of insulation if it is dry. And also,

    Best help, as you know, pre-heat the cooler with boiling or hot water. Let it sit for a few minutes with the lid in place and then drain. It minimizes the temperature drop when you add the wort.

    Keep the cooler inside during the cold weather.

    Don't be afraid to do a half-assed decoction. Nothing fancy, just draw a liter and heat it for a minute in the micro then return. Don't expect great control like this but if losing a few degrees is your concern this will help a little. Do it twice and tell people your beer is brewed with a double decoction. Three times and you can really impress with indecipherable German words.

    dmtaylor, PapaGoose03 and OldBrewer like this.
  4. HerbMeowing

    HerbMeowing Disciple (300) Nov 10, 2010 Virginia

    • Pre-heat the MLT.
    • Keep MLT off bare floor ... IOW let it sit on a folded blanket or towel.
    • Loosely wrapped blankets insulate better than ones wrapped tightly (trapped air is the insulator).
    • Place a barrier ... such as a pot's SS lid or length of AL foil ... atop the grain bed during the mash. No need to heat the space above the grain bed.
    • Insulate the lid with an injection of foam. IGLOO lids are solid. Donno about Rubbermaid.
    OldBrewer likes this.
  5. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    Thanks for the tips. I do preheat the cooler, use it indoors, and leave it off the floor.

    What I haven't done previously is add boiling water (if I open the lid, I will lose a lot of heat), use loosely wrapped blankets (I use a pillow on top, then 3 layers of blankets tightly wrapped over that), or add a barrier over the top of the mash.

    As for the insulation in the cooler, I added a lot of boiling hot water once and it significantly warped the inner wall, so that now there are "folds" inside. This may have affected the insulating properties somewhat. So it might be time for a new cooler, although the Rubbermaid has never been that good (I've always lost at least 4 or 5 degrees F since the beginning).
  6. Brewday

    Brewday Initiate (145) Dec 25, 2015 New York

    Maybe the square ones but not my round orange. Since i was modifying it anyways i added spray foam
    GormBrewhouse likes this.
  7. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    I just made a box out of 2x2 lumber, with a cut piece of paneling on one side. I made the inside dimensions (12" x 15") to just fit a heating pad. The cylindrical cooler fits nicely over this box (and also keeps it off the floor, although in my case, the box fits nicely on a small step ladder chair, high enough to allow easy draining later). The heating pad has three settings, and after experimenting with it, I will be using the highest setting. As suggested, I will also cover the top of the mash with a shiny lid, and loosely cover the entire cooler with blankets.

    The little heat coming in from the bottom, and travelling along the sides of the cooler under the blankets may help maintain the temperature of the mash better. Also, adding the lid will also hopefully help maintain the temperature better.
    GormBrewhouse likes this.
  8. pweis909

    pweis909 Poo-Bah (1,848) Aug 13, 2005 Wisconsin

    I'm not sure what the problem is or how you mash. One adjustment you might be able to make is to raise your water-to-grain ratio. With more a higher thermal mass, it ought to maintain temps longer. If the insulation box you built still doesn't do the trick, this could help.
  9. PortLargo

    PortLargo Devotee (465) Oct 19, 2012 Florida

    It looks like all the advice rendered is very non-creative (mine included). If you're really looking to impress the Poo-Bahs here's creative²:

    And this appears to be an article from someone who actually did it:

    Please post pics of your pressure cooker in action . . .
  10. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    Thanks, but my water to grain ratio is already reasonably high. I really think the problem is that the wall of the cooler is somewhat compromised. Also, using a 10-gallon cooler for a five gallon batch is not anywhere as efficient (in terms of overall heat loss) as doing a 10-gallon batch.

    But the real issue is the significant drop in temperature compared to when the cooler was newer (used to drop only 4 or 5 degrees and now drops 7 or 8 degrees over 1-1/4 - 1-1/2 hours), and how to compensate for it somewhat.
  11. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    Thanks, but no, I'm not out to impress anybody, and generally am interested in simple, practical solutions - otherwise I would already be using a Braumeister or RoboBrew. I'm still using the same Rubbermaid (actually Gott but almost identical) cooler that I started with over a decade ago. Like Charlie Papazian (who, I understand, continues to use his initial double bucket equipment to this day), I like to keep it simple for now (this could change in the near future as arthritis in my fingers is affecting my ability to lift heavy vessels). The steam approach does sound quite interesting, but is a little too technical for me.

    I could invest in a new cooler, but with the rapidly developing arthritis, I'd rather use the existing one for now, and save the investment for a RoboBrew or Braumeister or similar device in the future when needed.
  12. MostlyNorwegian

    MostlyNorwegian Zealot (531) Feb 5, 2013 Illinois

    I stopped brewing outside on our porch. That was my creative solution to avoiding those kind of temperature drops during the mash, especially during the winter where they were getting up to 10º on windy days.
    The other one was doing a decoction and raising it for the last part.
  13. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    All my mashes have been indoors, except a few times when it was quite warm outdoors (I almost always mash indoors and boil outdoors).

    I think you meant infusion, rather than decoction. I'm tempted to add some boiling water (maybe a liter or two) every 20 minutes or so. I could even add it without opening the lid, through a silicon tube attached to the outlet and raising the other end of the hose (attached to another vessel containing the boiled water) well above the level of the mash. It should spread reasonably well and evenly through the false bottom.
    #13 OldBrewer, Nov 30, 2019
    Last edited: Nov 30, 2019
  14. PortLargo

    PortLargo Devotee (465) Oct 19, 2012 Florida

    I can almost guarantee this will result in uneven temps throughout the grain. You seem reluctant to open the mash tun and add hot water . . . yes a little bit of heat will escape but more than compensated by ~1 qt of boiling water.

    When I add water it takes at least a minute of very hard stirring to equalize temps throughout. When I fly sparge I start with 185 water on the surface and temp probe shows the grain just below the surface happily swimming around in the mid-160s (after a mashout to 168). My point; it's hard to achieve even temp of the grain without some serious stirring.

    But again, this is not creative.
  15. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    I understand that it's hard to equalize the temperature when adding it from above (heat rises), but I assumed that adding it from below, underneath the conical false bottom, where it can spread out, and then forced upwards by the pressure from below, would allow the heated water to penetrate upwards and more or less equalize the temperature. But perhaps you're right in that even this approach may not distribute the heat evenly.

    When I remove the lid, a lot of heat does escape since there's a lot of air space above the mash (about half of the volume of the cooler), and the mash begins to cool. In 20 minutes, I would normally lose about 2 degrees, and perhaps even more when I open the lid and leave it open while stirring. I will have to experiment to see how much hot water I will need to regain 2-3 degrees each time. Adding a quart each 20 minutes means adding a full gallon of water to the mash. That does seem like a lot.
  16. MostlyNorwegian

    MostlyNorwegian Zealot (531) Feb 5, 2013 Illinois

    Nope. I'm boiling what I draw from the mash tun, and don't mess with adding from HLT until I go into sparge, and typically I do a 2 step sparge so I can get access to having a first running, and a second running in case I want to make two beers that brewday.
  17. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    So, are you drawing the mash out fairly early during the mash? To do a decoction, bringing it up to a boil and boiling it for at least 15 minutes, could take 40 minutes or longer. With a one hour mash, that means you would have to draw it off no later than about 20 minutes of mashing.
  18. PortLargo

    PortLargo Devotee (465) Oct 19, 2012 Florida

    I'm adding a little less than a quart while stirring . . . stirring every 20 minutes means two stir cycles or ~2 qts added in an hour. If starting at 1.4 qt/lb and add 2 qts that ends at 1.6 qt/lb, not a bad ratio to be mashing (assuming 10 lbs of grain).

    Not a rip, but you are overthinking this. A decoction is not what you want. I do one a year and it requires the previous day in meditation to gather the courage . . . can't imagine doing this regularly. I use the exact same mash tun as you and have adapted easily to a 1° drop every 15 minutes. If you can't live/adapt to that then buy a heavier insulated cooler and wrap it extra tight. Given enough insulation you will not have any loss of temp. If creativity is the goal then it's back to the pressure cookers.
  19. MostlyNorwegian

    MostlyNorwegian Zealot (531) Feb 5, 2013 Illinois

    Yeah, I pull it at like 15 to 20 minutes. But, No way. I'm not boiling it for 15 minutes. Seems like a bit of overkill since the only thing I'm looking for from it at this point during brew day is the temperature I can add it back in at, i.e. let it roll into a boil and add it back in. I'm going to boil the crap out of it soon enough, so get the temp right, and move on.
  20. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    I use a pillow on top of the lid, then three blankets. With that I lose 7 or 8 degrees F.

    Half of my response didn't make it for whatever reason. I think I added something like the following:

    "On the other hand, I could drain a quart or so of the liquid portion of the mash, boil it, and add part of it back every 20 minutes or so".
  21. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    Then it's not really a decoction, but more of an infusion. But draining a portion and adding it back every 20 minutes or so, would certainly work.
  22. PortLargo

    PortLargo Devotee (465) Oct 19, 2012 Florida

    How do you intend to get the boiling liquid back into the mash tun?
  23. dmtaylor

    dmtaylor Aspirant (225) Dec 30, 2003 Wisconsin

    I only mash for 45 minutes, so I won't lose as much heat as a longer mash. When temperatures fall, I will make a decision whether to add more hot water or to just let it fall. I've used both options almost 100 times and I still manage to make pretty good beer either way.
    MostlyNorwegian likes this.
  24. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    Open the lid, add and stir. Hopefully I won't lose to much heat by opening the lid.
  25. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    I understand that the first 20 minutes or so are the most critical. I'll lose about 2 degrees F in that time, which I guess isn't all that bad.
  26. MostlyNorwegian

    MostlyNorwegian Zealot (531) Feb 5, 2013 Illinois

    Goodness me, this is homebrewing, not commercial brewing. That's a very overthought question to ask for a yield of 5 gallons of beer.
    But, since you asked. By gently pouring it back in.
    PortLargo and hopfenunmaltz like this.
  27. PortLargo

    PortLargo Devotee (465) Oct 19, 2012 Florida

    Not trying to be overthought'ing but that was the idea in my first post. But OldBrewer's dilemma is heat escaping whenever he opens the lid. My suggestion was to open and add boiling water which accomplishes what you suggested.
  28. Steins_68

    Steins_68 Initiate (60) Mar 24, 2012 Illinois

    I can’t understand what you are doing to cause the mash temperature to drop by the amount that you say. I just brewed a 5 gallon batch of Milk Stout on Friday. I also use a 10 gallon Rubbermaid for my mash/tun, which is perfect for 5-6 gallon batches (by the way). I mashed-in to achieve my desired temperature. Every 15 minutes I stirred my mash to ensure an even temperature throughout the entire mash and to make sure the temperature hadn’t changed significantly. I also tested for conversation at 60 minutes. I say all of this so I can then mention that I normally don’t lose more than a degree or two over 60 minutes, even with the mash/tun being opened several times. By the way, I brew at the opening of my garage. This weekend the temperature was about 40-45F when I started. Are you confident with your temperature readings? And if you are losing that much heat you might want to consider investing in a new Rubbermaid cooler. It might be worth it if you reduce your concerns over temperature loss. By the way, most experts in the field say that the loss of a few degrees in mash temperature over 60 minutes will not likely have a distinguishable difference in beer quality or fermentability. So if you are thinking you must maintain the exact mash temperature for the entire mash, that is just not necessary.
  29. OldBrewer

    OldBrewer Aspirant (279) Jan 13, 2016 Ontario (Canada)

    Well, it's not really what I'm doing - it's what the mash tun isn't doing, and I already explained above why I think it's not holding heat properly. I have been using the cooler for just over 20 years. I also mentioned above why I'm not prepared to purchase a new cooler at this time, which is the reason for this thread asking for creative ways of maintaining the mash temperature (I'm not the only person who has been having problems losing a lot of heat with the Rubbermaid type of coolers). Yes, I'm very confident with my temperature readings, which I do after a thorough stir. I also use two thermometers to check the temperature - one of which has a very long probe. They are always consistent. For 10 gallon batches, I might only lose about 3 degrees F, but with 5 gallon batches, I lose 7 or 8 F over 75 minutes, especially if I open the lid a couple of times during the mash. Thus, it's not just a couple of degrees I'm worrying about, but a significant amount. The 10 gallon batches are of no concern - only the 5 gallon batches.