Thermometer error

[keith1664]

I've a bit of an issue with my first four AG brews in that only one has fermented down to it's predicted FG, the rest stopping somewhere between 1019-1021. I suspect it's due to my old Boots brewing thermometer being incorrect, Yesterday I tried it in boiling water and it under read by 2 degrees C, in iced water it read +2 degrees and today when my new digital thermometer arrived I had a difference between the 2 of 4.5 degrees at 60! So would mashing at 70 degress or so as opposed to 66 lead to this?

The new digital thermometer will be heading to work this week so I can have it compared to a calibrated reference, at least then I'll know where I am.

 

[Sean_Mc]

For £3 I find the Wilko ones better than any digital I've bought

 

[Vossy1]

So would mashing at 70 degress or so as opposed to 66 lead to this?

Quite possibly, but I suspect the temp could be higher. The higher the mash temp the more dextrins are produced and these are harder for the yeast to break down. Dextrins consist of non fermentable complexes and sugars which the yeast can break down over longer periods of time i.e., maturation.
Too many dextrins can lead to a high fg which in itself can make the beer overly sweet and unbalanced, if not targeted deliberately.

Let us know how you get on with the calibrated v the new digi :thumb:

 

[keith1664]

Just a quick update, according to our instrument workshop my £10 eBay digital thermometer is accurate to 0.1 degrees at 66 degrees C. That'll do.