Low FG when using cooler as mash tun

[abellote]

Hey all,

I always used a cooking pot to do my mashing and was getting good attenuation and good FG.
Then I got a 5gal round cooler and started using it as mash tun since I would get a better temp. control. I already did 5 batches using it and all of them ended with FG lower then 1.009 (one of them got as low as 1.005).

I started to wonder what might be wrong:
(1) Bad thermometer - Not a problem since I checked it against boilling water and it was good
(2) Mash Out - I didn't do it using the pot and I can't do it using the cooler since it has only 5 gal of volume and I can't get the amount needed of boilling water to get to 75C (167F). Should I do one? Anyone using cooler that doen't do a mash out gets good FG (>1.012)
(3) When I vorlauf and I'm lautering I noticed that the temp get as low as 60C (140F). Can the sugar profile change after the mash is done? I mean if I mash @ 68C (154F) I will get a sugar profile with a fermentability. If then I lower the temp. will enzimes keep on working breaking big sugar into smaller more fermentable ones? Or once the starch has been converted it really doesn't matter?
(4) I'm gettin to much cold spot in the cooler (maybe near the walls) and on my next batch I'll try to mix the mash every 10min or so. When you guys mash do you mix it often??

Any other ideas?? I wan't my beers to have more body!!

Thanks for the help

André

 

[jetmac]

Can you give us an idea of your process?

In other words, take us through your brew day.

 

[abellote]

Ok will try
1 - Grind grains and add it to the mash tun (cooler)
2 - Take grist temp and input it into Beersmith (BS)
3 - Heat mash water until I get the temp BS indicates
4 - Add water to grist mixing to avoid dough balls
5 - Check temp
6 - Add boilling water or cold to adjust temp
7 - Let it sit for 1 hour. I rarely mix the mash at this point.
8 - Vorlauf 3 or 4 times
9 - Fly sparge with water @ 80C (175-176F) while collecting the wort into a pot. (Sometimes the pot is already on the fire sometimes it's not). Even when I use sparge water at this temp I can't get the mash to rise over 70C (158F). And when the pot is not on the fire the temp can get really low. But even when I'm collecting the wort and heating it I also get low FG.
10 - Boil and so on....

I try to follow everything I read on the books (How to Brew is a reference) and here on the forums.

I'm using this cooler:

Hope this helps...

 

[Hammy71]

It seems to me that you must be mashing to low if your attenuation is that great. What mash temp are you shooting for? Like you said, either your thermometer is off or you are loosing way to much heat out of that cooler.

 

[abellote]

I used to mash @ 67C (153F) now I'm going to (155-156F).
But my temp only drops maybe to 149F at the end of an hour...

 

[Gregscsu]

What type of thermometer do you have. Standard dial thermometers are notorious for being as much as 10F off at mash temps, even if they read correctly at 32F and 212F

 

[abellote]

I'm using this one:

I checked it.. in boilling water it reads 96.7C the temperatura that water boils here (at an altitude of 960m (3150ft). When I stick it under my arm it reads 36.7C (98F). I also have a regular one which reads 12F off this one. I also used the same thermometer on my earlier batches, the ones that I was getting good FG.

 

[Yooper]

I used to mash @ 67C (153F) now I'm going to (155-156F).
But my temp only drops maybe to 149F at the end of an hour...

But you said you're in the low 140s by the time you finish sparging? If so, you need to increase the sparge water temperature, as I see #3 as a big problem. You're correct in that the debranching enzymes will continue working, and increase the fermentability of your wort until you get to mash out temps.

What I would suggest is that since your cooler is too small to mash out with, then try batch sparging. What you can do is two rounds of sparge water additions, and add the first round of batch sparging HOT. Mine is usually 200 degrees, which works as a mash out for me. It gets the grainbed to 168 degrees, and then I stir well, vorlauf and drain. Then repeat with 170 degree water. This serves as a mash-out so to speak.

The other thing to do is to get your runnings on to boil as they leave the MLT. That also helps "preserves" the mash profile.

 

[abellote]

By the end of the mash (1hour) I'm at 149F. After vorlauf and sparging is that I go to the 140s.

I'll try to do a batch sparge next time using the temp. profile you suggested.
I was just wondering if other people using coolers have the same problem. Here in Brazil I'm the only one that I know that uses coolers as mash tuns.

On my last batch I got my runnings to boil after they leave the MLT. My FG was 1.009 (not that bad since I was getting 1.005-1.006).

I only wonder why other people don't have this sort of problem and why I was getting good FG when usin a top oven pot to mash. At that time my running would go as cold as 113F and "preserve" the sugar profile. Maybe the contact with the hot bottom acted as a mash-out??

Thanks for the help.

 

[jetmac]

A couple things that may help ease your process.

Add the strike water first then let it settle to the desired temp BS suggest's.

For example> BS says to add 167F water to grains. The way to do it is to add your strike water first but at a little higher temp. So what you may want to do is add 170F water to your cooler then let it cool to desired strike temp of 167F. At which time you would add your grain to the water. This helps get your cooler keep the temp and is alot easier to keep from forming dough balls. And you may want to wrap a blanket or comforter around your cooler.

You don't say if you use a manifold or false bottom or braided line. As yooper suggests, a batch sparge may be a better option. Don't get caught up in all the hoopla of fly sparging. It requires more attention and more moving parts.

There is some discussion of whether it is necessary to heat your sparge water for batch sparging or not. I do. But regardless, you can do 2 sparges when batch sparging. You don't even necessarily have to let the sparge water sit in the cooler for more than a couple min .

One more thing, keep in mind that your cooler is pretty tall and your thermometer is probably only 6 inches long, so you are only checking the temp of the top 6 inches. I would almost guarantee the grist at the bottom of your cooler is much hotter. They do make bungs and thermometers to fit in the side of a cooler.

 

[abellote]

Thanks for the help jetmac

Things to try on the next batches:
1 - Double check my hidrometer (maybe it decalibrated)
2 - Pre-heat mash tun
3 - Do a batch sparge with hot water to act as mash-out
4 - Stir the mash more often maybe every 5-10 min.

I'm using a copper manifold that's the reason I tried fly sparge. Maybe I'll get back to batch sparge and use some more malt to compensate for the loss in efficiency (if any at all).
I'll also try to get one of those thermometers that fit in the side of the cooler, my only worry is that it will disturb me while I'm stirring the mash.

Thanks for the help.

 

[thisoneguy]

Two things that really helped me keep mash temps constant are:

1. Drill a hole in the cooler lid and fill it with foam insulation (a few bucks for a can)
2. Wrap the cooler in blankets. I put one under mine, and then drape the thickest one I have over the top and sides.

I used to lose 5-10 degrees in an hour. Last time I brewed I lost only 1.5 degrees in 60 minutes. YMMV