How to check mash temperature

[Martybhoy]

During my brew last Saturday, I struggled to get a consistent mash temp reading.

It was a fairly thin mash (32ltrs with 6kg of grain). I use a Thermapen probe thermometer, which was calibrated at 0° and 100°.

My problem was that the temp in the top 6 inches of the mash was perfect. When I drew a little wort out of the tap, I measured the temperature right at the point of exit, and it was about 8° higher. This was after a really good stir.

I have a steel mash tun and a steel ball valve tap. Could the steel tap cause the temp of the wort to increase as it passes through? Almost like a mini pasteurization?

I'm struggling to work out why the mash temp would be different in the bottom half compared to the top.


Any suggestions?

 

[chewie]

Are you using a heat source to apply heat during the mash at any point?

 

[Martybhoy]

No. I fill the tun with water at strike temp then add the grains, mixing as I go.

 

[henteaser]

Is there a false bottom that could be holding some strike-temperature mash (i.e. hotter) away from your stirring effort?

 

[Martybhoy]

There is a false bottom, yes. And there is no dead space, so all water goes via the false bottom on the way out.

If that's the cause, then if I drew a couple of litres or so (which I would add back), the temp may settle.

I'll try this at my next brew. Cheers

 

[Ajhutch]

It is worthwhile trying to have a few different thermometers. I have a probe thermometer on my mash tun which tends to be near the top depending on the precise grain bill and water volume and I've got a standard glass mercury thermometer that I shove down to the bottom of the mash and check every 10 minutes or so. I could recirculate using a ball valve and jug but I don't tend to bother, I just stir if they get out of alignment too much.

 

[Gunge]

I observe a difference in mash temp at the top and bottom of the tun ( a Coleman Extreme which is pretty damn good ) every brew day. Cooler at the bottom, hotter at the top. Just physics I guess but if the lower and higher readings are within 62 - 69C I'm ok with that, just give it a good ol' stir halfway thru to equalise things. Beer turns out great anyway.