Thermometer calibration

[Wrighty69]

Working through possible causes for ferments stopping at 1.020 recently and i'm wondering if my mash temperature is out. Have always used a UK made glass thermometer and tested it in boiling water tonight with a spare glass one and two digitals. The glass give similar readings but the digitals are five degrees or so higher. I'm also confused by all thermometers reading in the 80's for kettle boiled water. However, I am 270 meters above sea level so wondering if this is a factor? My SG is normally where it should be according to recipe calculators and my pitch temps tally with stick on thermometers. Any advice gratefully received.

 

[Larse]

Kettle boiled water drops temperature quite quickly after the boil. In the 80s would not be unusual. Altitude has some bearing, maybe one or two degrees lower boiling point. That's the same across the board, so if you're mashing at 66, you may be closer to 64.

You say recently. Has something changed in that period? Fermentation stopping early is generally yeast related.

 

[Buffers brewery]

Just used this….

https://www.omnicalculator.com/chemistry/boiling-point-altitude

to check boiling point at 270m and normal pressure, 99C
All my digital thermometers give different readings, consistently.
I suggest boiling some water in a saucepan to check the boiling point reading.

 

[Sadfield]

https://beerandbrewing.com/how-to-c...ext=To calibrate your thermometer for,F (0°C).

 

[Wrighty69]

I've tested three digital and two glass thermometers this evening. At the extremes there's slight discrepancy but at the crucial 60-75c it would appear the digitals tally and the glass is around 6 degrees cooler. Looks like i've been mashing around the 70+ mark and pitching yeast above 22c. Hence ferments go off like a rocket but then burn out within a day and so and I get the dreaded 1.020. Looking forward to the next brew day with a bit more accuracy.

 

[Larse]

I've tested three digital and two glass thermometers this evening. At the extremes there's slight discrepancy but at the crucial 60-75c it would appear the digitals tally and the glass is around 6 degrees cooler. Looks like i've been mashing around the 70+ mark and pitching yeast above 22c. Hence ferments go off like a rocket but then burn out within a day and so and I get the dreaded 1.020. Looking forward to the next brew day with a bit more accuracy.

That's a massive discrepancy. Very unusual for a spirit thermometer. Especially since it's in the middle.