Reynard
Guru
BTW depending on the accuracy of your thermometer (worth testing in water at a rolling boil ...) and also on the amount of heat held by the bowl or jug or whatever you use, you might need to stop heating, or continue heating, for a half or one or two degrees more or less than the 85 degC quoted. No more, and keep a note of it so you will know where best to 'stop' next time.
I have a sugar thermometer, left over from when I used to make my own sweets. That'll do.