Author Topic: Inaccurate thermometers  (Read 2818 times)

Offline MFigz

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Inaccurate thermometers
« on: October 16, 2016, 07:26:49 PM »
So I'm having some trouble hitting my OG. I was reading somewhere that mash temp could be one of a couple of factors. I've done the icebath test in the past and all 3 of my thermometers were accurate. For the heck of it today I used my electric water kettle to heat some water up to 155. My dial thermometer read 146 degrees, my thermoworks electric meat thermometer read 148 degrees, and the "lab thermometer" that I just bought from my LHB store read 154 degrees. In an ice bath I double checked and they all read 32 degrees. How do I know which one is accurate?

Thanks!
Mike

Offline Oginme

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Re: Inaccurate thermometers
« Reply #1 on: October 17, 2016, 05:23:31 AM »
In terms of your thermometer issue, pick one and stay with that for your mash temperatures.  I would also do a check in boiling water to see which is more accurate at that end.

In terms of not hitting your OG, that is more of an extraction efficiency issue (I am assuming that you are doing all grain).   I would look at the grind of your grains as the first step.  Make sure there are no intact kernels which do not break apart easily upon squeezing.  The grain bits should be around 1/8" (~3 mm) with a little dust and fairly intact, but mostly empty husks.  Brad just put up a blog on grain crush a week or so ago and you can look that up on the main BeerSmith site.

After that, the other big problem would be making sure that all your grains get thoroughly wetted when mixing them into the strike water.  You want no dough balls or clumps of grains. 
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Offline GigaFemto

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Re: Inaccurate thermometers
« Reply #2 on: October 19, 2016, 05:00:17 PM »
My experience with kitchen or meat thermometers has been miserable. They are not very accurate, have poor resolution and are not always adequately waterproofed for measuring mash temperatures. I finally bought a Thomas fully waterproof unit with calibration certificate that is traceable back to NIST. It cost $30, but it is worth it for the peace of mind and better readings.

Having said that, mash temperature is probably not your problem with hitting OG as long as you are in the correct ballpark. My first mashes had efficiencies of about 40% before I figured out that my water has a pH of 9.3 and I need dark grains or acidulated malt or phosphoric acid to bring the pH down. I bought a pH meter and I check my mash pH to keep it in the 5.2-5.6 range and I now get efficiencies of 65% - 70% and hit my gravity targets on the nose. I also run my grains through the mill at my LHBS three times to make sure they are milled fine enough.

GF

Offline MFigz

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Re: Inaccurate thermometers
« Reply #3 on: October 20, 2016, 12:30:04 PM »
Thanks a lot for the feedback. Crushed my grain at the LHB store. It looked well crushed and there was a decent amount of powder. Maybe I'll take your advice and crush it a couple more times just to be sure. As for the thermometer, I think I will look at a certified one for next time. With mash temps being so critical within a few degrees I don't feel comfortable just picking one and sticking with it. At the readings I am getting that could bring me from a medium-bodied to a light or full-bodied beer.

Thanks a lot for the suggestions!
Mike