How much temperature should a cheap ice cooler drop during mash?

[Nava854]

My father and I are just adventuring into all-grain using the BIAB method.
I have an old 30L (8gal) ice cooler that I was planning to repurpose as a mash tun. I’ve been experimenting with just water to see how well it holds the heat, but it drops 4.9 degrees Celsius (~8.8 F) over 1 hour with 22L of water @ 65°C/149°F. Ambient temperature was 22°C/72°F.
That sounds like a weak performance, but I am not sure. How much should I expect the temperature to drop in a cheap ice cooler?

Right now we are working on insulating the cooler with styrofoam sheets, but it I think it kind of defeats the purpose of using an ice cooler in the first place.

 

[3 Dawg Night]

That is a pretty big drop. Mine only drops 1-3F over 60 minutes. There's a couple of things you could do:

1) Get a new cooler (they're not that expensive).
2) Wrap a blanket or sleeping bag around it during the mash.

Honestly, I'd give #2 a try first (do your same water test) and see how much of a difference it makes.

There's a big difference in mashing at 140F vs 149F or 158F vs 149F. Those temperatures will make three different beers (but it will still be beer).

 

[Nava854]

Truth be told, this cooler is cheap and veeery old and I’m inclined to believe that it would be worth buying a new one. But my father argues that a new one will perform exactly the same while I believe that it won’t.

And yes, I'm painfully aware of the temperature ranges at which conversion takes place. That is why we are worried by the poor performance.

 

[bracconiere]

thermal mass matters too. plain water i believe will lose heat a lot faster then a thick mash.....

 

[brew_darrymore]

You can't test the temperature drop just by using water. As @bracconiere said, the thermal mass matters, so once you add the grains, it's likely you'll lose a degree or two at the most. I cover my mash tun with a blanket or sleeping bag for extra insulation.

My mashes usually lose 1-2°F over 60 minutes.

 

[RM-MN]

Truth be told, this cooler is cheap and veeery old and I’m inclined to believe that it would be worth buying a new one. But my father argues that a new one will perform exactly the same while I believe that it won’t.

And yes, I'm painfully aware of the temperature ranges at which conversion takes place. That is why we are worried by the poor performance.

I have good evidence that your father is wrong. Go look at a 5 day cooler. They will keep ice from melting for 5 days. Try that with the old cooler. Coolers are not that expensive.

Now for the other side of the equation. You lose nearly 5 degrees C during the mash period. How much do you lose while the starch to sugar conversion is going on. Hint: The time for conversion may not be even close to the mash period. It could range from less than 10 minutes to over 2 hours.

 

[madscientist451]

Did you pre-heat the cooler/mash tun with hot tap water?
How many gallons of water were in your test?
The more hot water you put in there, the more thermal mass you have, the longer it will hold a steady temperature.
Put a piece of aluminum foil on top of the mash and then use an old sleeping bag for extra insulation.
I used to BIAB in a cooler, but now I just use the pot on the stove. My electric stove has the smooth glass top that holds some heat, I wrap up the pot in an old coat and keep a pretty steady temperature for an hour.

 

[Jim R]

I heat up 3-4 gallons of water to 170-180 degrees to preheat my cooler for 15 min or so before the mash which slows down cooling considerably. I also keep some hot water on hand and add it if the temperature drops too much after 30 min or so. Since the majority of the mash takes place within the first 30 min, it probably doesn't matter if it drops a little more over 60 min.

On the other hand, a 5 or 10 gal cooler doesn't cost very much.

 

[belgabrewing]

I bought a used 10 gallon (5 gallon may be too small for "bigger" beers) Rubbermaid water cooler on Craigslist/ OfferUp. It drops 1-2 degrees over an hour. I picked the Rubbermaid over Igloo because the hole for the spigot is designed so a 1/2 inch stainless close thread nipple fits better with the stainless lock nuts to make a waterproof connection. Rubbermaid also works better because of the threaded lid instead of a friction fit on Igloo which can pop up.

 

[Lalo_uy]

A no brand 27L cooler hold ok with no more than 2C cooling in 60min. At 67C.
Keep it closed all the time.

 

[CascadesBrewer]

I picked up a sleeping bag from Walmart for around $25. On a cool day, even with opening it at 30 mins for a good stir, I often lose only 1F to 2F over a 60 min mash.

 

[Dancy]

Using a 10G Igloo cooler, 10-12lbs of grain, in my kitchen and mashing 154 degrees — lose 2 degrees. I put Reflectix on the lid, figuring heat rises.

 

[3 Dawg Night]

Using a 10G Igloo cooler, 10-12lbs of grain, in my kitchen and mashing 154 degrees — lose 2 degrees. I put Reflectix on the lid, figuring heat rises.

I've also heard that some folks drill a couple of holes in the top of their lid and fill it with expanding spray foam insulation. I have a can of it in my shop, but I haven't tried it yet. I do think that's where the majority of my heat loss is occurring.

 

[Mark3885]

The round igloo type water coolers have a hollow lid. I drilled holes in the underside of the lid and injected small crack filling foam . Don’t add too much ( drill multiple holes) the foam will expand the lid .
With preheating the cooler mash tun with mash water 5 degrees above the calculated temperature, I will add all the mash water then add grain and stir until the temperature drops to the mash temp

 

[CascadesBrewer]

My father and I are just adventuring into all-grain using the BIAB method.
I have an old 30L (8gal) ice cooler that I was planning to repurpose as a mash tun.

If we back up a little... I am not opposed to mashing in a cooler or repurposing items for whatever type of brewing. One of the appeals of BIAB is doing full volume mashing in the same vessel as using for boiling. An 8 gallon cooler is not going to be big enough for a full volume mash (for a 5 gallon batch). It sounds like your setup leans more toward a 3-vessel setup with a sparge.

How large of a kettle do you have? A 10 gallon kettle is a decent size for full volume mashing for a 5 gallon batch. Then you can skip the cooler.

 

[ajm163]

I've also heard that some folks drill a couple of holes in the top of their lid and fill it with expanding spray foam insulation. I have a can of it in my shop, but I haven't tried it yet. I do think that's where the majority of my heat loss is occurring.

be careful here I tried this (and at least with the foam i used) it was a mess. The mash heated the foam past the melting point and i had a sticky foam mess oozing out of my cooler lid for the whole mash. it was a huge pain

 

[Barbarossa]

I would be more worried about the toxicity of the old plastic than losing heat. And I would be worried to lose heat. I didn't dare to use my cheap Coleman cooler because it does not mention that it is food grade.

 

[3 Dawg Night]

I would be more worried about the toxicity of the old plastic than losing heat. And I would be worried to lose heat. I didn't dare to use my cheap Coleman cooler because it does not mention that it is food grade.

Wait, why wouldn't a water cooler be food grade?

 

[Barbarossa]

Well I tried to look for the info and found nothing. They don't mention it being food grade. All I found was this:

Non-toxic When Used as Intended:Yes

Hot/Cold:Cold

I assumed that using it for hot liquid was not using it as intended and maybe unsafe. That's all I got. I didn't dare.

 

[3 Dawg Night]

Ah, I see. I wasn't thinking hot vs. cold. The description for mine explicitly stated that it was good for hot or cold liquids.

 

[Barbarossa]

Ah, I see. I wasn't thinking hot vs. cold. The description for mine explicitly stated that it was good for hot or cold liquids.

Yeah I bought the cheapest one lol

 

[Nava854]

I just checked the thread today, and all I can say is thank you so much for all the amazing answers.
A couple of things I want to comment before I leave this for good.

I used a sous vide and cling film to heat up the water inside the cooler (because laziness) and it took more than 30 mins, so my guess is that the temperature of the cooler was already close to mash temp.

I used 22 liters (5.8 gal) for the experiment to simulate the 15 liter (4 gal) batch we're making by adding the same weight of water as malt. Because the specific heat capacity of water is very high, it is very likely that it's also higher than that of malt. That means that the thermal mass of a real mash will be lower, and I believe the loss will be greater... unless the convection was impeded by the floating grain? Actually that would be an interesting experiment to make.

Right now we are interested in doing the mash in a cooler because our heat source is too powerful for mashing in the pot. But in the future we might upgrade our kettle to simplify stuff and do everything in the same place.

And no idea about the toxicity of the plastic. That could be a concern.

Anyway, for this batch we will be using free styrofoam sheets that my friend gave me to insulate the cooler even more and call it a day. And for the next one I'll be buying a new cooler and throw the old one while my dad isn't around. (wink)