Paul vs The Laws Of Thermodynamics

[WelshPaul]

I have been making a brew this morning and have ancountered a strange and infuriating problem.

After preheating the mashtun and getting 19 litres of mash water to 68.5°C, I put the grain and waster in (grain temp was 21°C) and the temperature dropped to 59.7.
No problem, it's to be expected. So, I added a full kettle, 1.9l, of boiling water, only to see the temperature stay tubbornly at 59.7...
Cue second kettle. Temperatre nudged up to 60.0°C only to fall back to 59.7.
Third kettle.
Fourth kettle.
Now, after adding nearly 8 litres of boiling water to the mashtun, the temperature is holding at, yes you guessed it, 59.7°C!

Has anyone ever encountered anything like this before as it has me baffled?

 

[WelshPaul]

I suppose the real question is, is this batch completely lost? Can I get any sugar extracted if the temperature refuses to get to 66°?

 

[snail59]

Did you give it another good stir as the probe could just be sitting in a thermal cool pocket.

 

[WelshPaul]

I did, but it didn't seem to make much of a difference. I've gone ahead and done the boil phase just to see how it turns out.

 

[paulpj26]

I'd be more inclined to think you might have a dodgy thermometer?

 

[WelshPaul]

I'd be more inclined to think you might have a dodgy thermometer?

It works fine in measuring everything else - I think that maybe I just managed to find a few cool pockets, as improbable as it is.

 

[Runwell-Steve]

My money is on the thermometer.

You had a total of 27 Litres of water with an average temperature of 78 C.

There is NO possible way that mixing in 5 Kg of grain could reduce the overall temperature down to 59.7. It just can't happen.

That amount of grain at that temperature would reduce the temperature of the water by 4 degrees C at most, certainly not the nearly 20 degrees that you thermometer is saying.

Either your initial water was not at 68.5, or the readings taken after that were wrong.

What sort of thermometer have you got, is it one where the probe is on a lead, of so these can often give false readings as moisture can get inside the probe.

 

[dennisking]

Agree with Steve. I am always double checking my mash temp. with a digital and a standard thermometer

 

[WelshPaul]

It's the probe on a lead type, yes. OG came out at 1.061, which was a little over what I was aiming for so I'm hoping it's OK.
Funnily enough, the second brew that day (double brew day - never again!) measured fine; this time I heated the mash water to 74°.

 

[Moley]

The grain will usually take around ten degrees out of the mash liquor temperature, so your strike temperature should usually be around 10-12°C above your desired mash temp.

I get my mash liquor to 78°C before doughing in because I find it easier to adjust the mash temp. down a little if necessary.

 

[Runwell-Steve]

Thats a huge temp drop Moley, It just shows how different peoples systems react differently.

I underlet so need to get mt Strike water spot on before I add it to the Mash Tun. I aim for a Strike Temp of 71.5 degrees C, which I then add to the grain and end up with a Mash Temp of 66 C. So I have a total loss in temp of 5.5 degrees to the grain, at a liquor to mash ratio of 2.5:1.

Assuming Paul was using 27 Litres of liquor and I am assuming 5Kg of Grain maybe more, he had a liquor to mash ratio of 5.4:1. There shouldn't have been much drop in temperature. Even with 10Kg of grain there would be a ration of 2.7:1 which is similiar to what I have.

 

[WelshPaul]

I used 7.7kg of grain, which was quite a lot for a 23l brew. I'm going to try heating the strike water to 74° next time to see how it goes.