I liked doing the plate method better than the thermometer. Last time I made this jam I thought I cooked it too long trying to get the temperature up to 220 and my jam looked very dark in color. I like a deep crimson red for the jam. This was something my mom was always striving for. She never used a thermometer or the cold plate. Her jams were good but never consistent in color.
I hope this inspires you to try to make some jam. It really is easy and it tastes great!