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Old 07-14-2009, 06:56 PM   #1
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Default Mash Equations for 10 gal Rubbermaid Coolers

I've got the same 10 gal big orange Rubbermaid Cooler that just about everyone has on HBT. I've been hit or miss on more than a few of my mash temps. I use Beersmith and it gives me a ball park but it never equates for cooler temp because of the lid, sides, etc. As many of you know, the cooler will hold temp for easily over an hour without 1 degree fluctuation. It's just hitting the initial temp that's the problem.

What I'm proposing is a spreadsheet that tells you how much water at what temp will go into your cooler for your amount of grain. I'm proposing that we do everything in pounds/ounces and ferinheit. I'm also proposing that we do this with the assumption that your grain is at room temp and you have not preheated your cooler. I know it's easier to preheat but we'll have an inconsistant variable by not knowing how much you've actually added to your cooler for how long and and what temp to do the preheating.

I'll collect the data once it gets to a sufficient size and report in spreadsheet style.


Here's my first equation for the mild that I'm brewing today:

(7 pounds 11 oz) in 2.5 gal of 168F water = 158F Mash temp
(16 pounds) in 5 gal of 167F water = 154 mash temp

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Old 07-14-2009, 07:48 PM   #2
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Well....I have the Rubbermaid (Home Depot branded) 10 gal. "big orange" cylindrical cooler, and I've had difficulty not losing 4 degrees in an hour mash. Yes, I preheat, yes I mix thoroughly with paddle, yes I cover the cooler with a heavy blanket, yes I keep it up off the floor, and yes I put a block of foam over the brass ball valve to keep from losing heat that way...and it'll still go from 152F - 148F in the hour. After three batches, I finally insulated the lid (which comes with NO insulation) with some of that "Great Stuff" product in the ærosol can, and we shall see when I brew next time.

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Old 07-14-2009, 08:20 PM   #3
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I guess I'm a lucky one. I've never done any of those things and I do fine. Hopefully that will cure your problems.

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Old 07-14-2009, 08:27 PM   #4
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The thing is, I mash in with a preheated cooler, which then would change the temperature of the necessary strike water so your spreadsheet wouldn't work for me.

I never lose more than a degree or two, so I'm uncertain as to why you are, rico. That seems really strange. Of course, one of the "insulators" is the grain itself, so in a very small batch, I can see it losing a little heat. I don't use any extra insulation, don't cover the ball valve, etc, so I'm surprised your experience is so different that mine.

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Old 07-14-2009, 08:43 PM   #5
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eschatz, it seems like this would be more of a issue for the "add water to grain" crowd than the "add grain to water" crowd. Which are you? Beersmith and other strike water temp calculators (online, etc.) always get me really close on mash temps. I add grain to water.

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Old 07-14-2009, 08:47 PM   #6
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why would it make a difference? you end up with the same temp whether you add the grain first or second. it could be that I'm just stupid. actually it's probably that I'm stupid but I'm not getting this. I've seen people debate this before but I've never given it much attention.

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Old 07-14-2009, 08:56 PM   #7
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Are you estimating the temperture of the grain correctly? I find that when my mash temp is off a couple degrees, it's usually on a day where my garage has fluxuated by a big swing and the grain in the bag is warmer or colder than I thought.

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Old 07-14-2009, 08:59 PM   #8
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I dont know. I've never really thought about it. I believe my grain to be room temp. I don't know anything that would make me think otherwise.

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Old 07-14-2009, 09:01 PM   #9
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I agree with the grain temp issue. I have the same cooler (the Home Depot version) and have never lost more than 1-2 degrees, even over a 90 minute mash. I don;t use beersmith though, I use beer alchemy. I set ambient to 75F and heat to about 8 degrees over that. I put the lid on and let it sit for 5-10 minutes and take temp. Once it reaches what Beeralchemy says it should be, I dough in. I'm almost always on target, sometimes a little high, so i add cool water. I have never covered te cooler, or done anything else to prevent heat loss.

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Old 07-14-2009, 09:05 PM   #10
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Quote:
Originally Posted by eschatz View Post
why would it make a difference? you end up with the same temp whether you add the grain first or second. it could be that I'm just stupid. actually it's probably that I'm stupid but I'm not getting this. I've seen people debate this before but I've never given it much attention.
So, you add water to grain? Not trying to bring up the old this vs. that battle. Either way you end up with beer.

Just seems to me that it's easier to heat strike water (I start with 175ish water) and add it to the MLT, let that water heat up the cooler insulation material or whatever it is you're using as a MLT, and let everything equalize (mine drops ~10* in this process, getting me to around 165*). Then gradually let the temp drop by waiting or stirring for a minute down to my calculated strike temp.

That's when I add the grains, give it a good stir, wait another minute for things to equalize, and take a temp reading. It's been pretty close on the batches I did in my cooler MLT. Make a note of how far off you are and adjust up or down on the strike temp next time.

I tend to err on the high side rather than low so that I can add a wee bit of cool water to adjust down to my target mash temp if necessary. It's easier than adding boiling water to bring it up if I'm low to start with.

I think it's important to give a few minutes for temps to equalize before taking a reading. I'd guess a lot of people rush that step. Could be one reason that some people claim to lose 3,4,5* over an hour, when really they're losing it in the first 5 minutes before the temps have balanced out.

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