Mash temp issues

[Blackhawkbrew]

The last several batches I've been having trouble holding my mash temps. I've been using the same Rubbermaid rectangular cooler since I started all grain about four years ago. I've tried putting a blanket around it and that helps a bit but temps still drop three to four degrees over the hour mash. I'll start out at about 152* and end up at about 148 by the end of the mash. Might be time for a new cooler.

 

[Denny]

That's really not much of a problem.

 

[unionrdr]

I do partial boil partial mash biab. I do like 5-6lbs of grain in 2 gallons of local spring water. I spread out my winter hunting coat with two pot holders on the inside back of the coat to set the BK/MT on. pull the hood over the lid,wrap the sides around,& tie the sleeves once. Last Sunday I didn't tie them very tight,& the temp went down from 152 to 148F just like yours.
Then last Wednesday,makin another PM IPA,the mash water heated up really fast to 170F. Let it cool down while weighin out hops. Temp down to 152F...cool,all set. By the time I stirred the grains in,broke up dough balls & all that,it went down to 148F. I tied the sleeves tight this time,unlike last time. Over the one hour mash,the temp went up to 156 even! That kettle was steamin when I took the lid off after unwraping it. So it seems any insulation must be tightly wrapped to be the most effective.
Holes or cracks in the outside skin of a cooler will make it loose insulating ability as well.

 

[GrogNerd]

I do partial boil partial mash biab. I do like 5-6lbs of grain in 2 gallons of local spring water. I spread out my winter hunting coat with two pot holders on the inside back of the coat to set the BK/MT on. pull the hood over the lid,wrap the sides around,& tie thwe sleeves once. Last Sunday I didn't tie them very tight,& the temp went down from 152148F just like yours.
Then last Wednesday,makin another PM IPA,the mash water heated up really fast to 170F. Let it cool down while weighin out hops. Temop down to 152F...cool,all set. By the time I storred the grains in,broke up dough balls & all that,it went down to 149F. I tied the sleeves tight this time,unlike last time. Over the one hour mash,the temp went up to 156 even! That kettle was steamin when I took the lid off after unwraping it. So it seems any insulation must be tightly wrapped to be the most effective.
Holes or cracks in the outside skin of a cooler will make it loose insulating ability as well.

air does make a poor insulator

I've been adding a layer of aluminum foil to the top of my grain bed, that has helped a lot to maintain mash temps

 

[bottlebomber]

That's really not much of a problem.

This, even 5 degrees over an hour isn't bad. If you hit your temp with the strike water, most of the work is done in the first 15-20 minutes anyway. Unless your cooler has split or the insulation got wet it works just as well as the day you bought it. Is it possible that you aren't preheating your MT sufficiently? The mash loses a couple degrees right away, I figure that in when I heat my strike water.

 

[Komocabo]

Reflectix works great on my keggle MT. I lose 1-2° during a 60 min mash. Don't see why it wouldn't works as additional insulation for a cooler...

 

[Blackhawkbrew]

I preheat my mash tun by adding my strike water at 175*. It drops to about 165* and I let it sit nail it stays at the same temp for a couple minutes. I add my grains and stir until I hit my mash temp. Today my pre boil gravity was way down, called for 1.056 and I was at 1.047! I did a late addition of DME (one pound). I think I should check my thermometer and hydrometer.

 

[Denny]

I preheat my mash tun by adding my strike water at 175*. It drops to about 165* and I let it sit nail it stays at the same temp for a couple minutes. I add my grains and stir until I hit my mash temp. Today my pre boil gravity was way down, called for 1.056 and I was at 1.047! I did a late addition of DME (one pound). I think I should check my thermometer and hydrometer.

How long do you stir? Do you check the mash temp in more than one place?

 

[Blackhawkbrew]

I have a temp probe in the mash. I mix the mash around until I get to the mash temp. Sometimes I move the probe around.

 

[Denny]

I have a temp probe in the mash. I mix the mash around until I get to the mash temp. Sometimes I move the probe around.

Keep stirring and move to probe to different locations and depths until you get the same reading everywhere.

 

[unionrdr]

air does make a poor insulator

I've been adding a layer of aluminum foil to the top of my grain bed, that has helped a lot to maintain mash temps

Air only makes a good insulator when it's trapped. As in the isulation inside a quilted winter coat,quilt,or the like. That's why goose down or Thinsulate lined/quilted coats are so warm. The "poofy" stuffins in those kind of coats are purposely designed to trap air against the body to preserve body heat next to the skin. But it has to fit snugly to work properly.
So again,the air has to be trapped. I got it right by wrapping the sleeves tighter around the BK/MT in order to more properly "trap" the air & keep more heat inside. Thus,the temp rose because there was no air movement.
That's why my quilted hunting coat works so well. Got it at Gander Mountain.