Share 'Lava lamp overheating chart'

I’ve seen so picture charts with the different flows and if it’s to hot or cold  but the just right and the slightly too warm look the same to me in the pictures so I can never tell if/ when I should turn on my dimmers. What should I be looking for specifically and how much do I dim the lamps because sometimes I will turn the dimmer on and it stops flowing like it got to cold