a picnic cooler
150.7F - Close enough!
Covered to hold heat
The temperature should stabilize with a couple of minutes to the desired temperature, in this case I was shooting for 150F
As you can see, I ended up with an initial temperature of 150.7F. Not too bad!
I get asked, "what if the temperature is too high? What is too high? Too Low?"
First, what is too high? Mashing takes place in a general range of 147 - 160F. Low range takes longer and is a thinner, more fermentable, higher is more body / dextrenes... Most recipies will call for a single stage at 150F. IMHO, if you are +/- 2F you are just fine. If you are too hot, just open the lid and stir and allow to air cool as you stir, also perhaps you can stir in a cup or two of cold water (be careful! It is easy to overshoot with cold water!). Relax.
To cold? Try adding a quart of boiling water... Stir well...
Bottom line, don't worry too much, you shouldn't be too far off. There are spreadsheets and commercial programs that can help with the calculations and calibration of your system.
Cover up the picnic cooler to help retain heat. Set timer for 90 minutes.
During the 90 minutes, my temperature slowly dropped from 150.7 to 148F. I don't do an iodine test for starch conversion... I just don't :)