While scrolling the internet I came across the classic Galileo thermometer, mainly used in the household the thermometer generally reads between the temperatures of 18C to 26C but could I use this method to tell the temperature of the water being heated for my tea?
Galileo thermometers work on the principle of changing densities in water and each bulb has a slightly different weight calculated to float at a certain temperatures but when the water goes above this temperature the bulb will sink.
I believe that this method of taking the temperature is a more elegant alternative to using electronics and lights.
More experimentation will be required to check this method will work so more updates will follow!!