pre heat test for your dutch oven

I found this on an Australian D.O. forum.
Simple and practical
Testing camp oven heats by paper test
Here’s a way to determine the heat of an oven when using coals from a fire.
Pre-heat the oven on a bed of coals. Place a piece of paper inside the oven to find out what heat the oven is at. The paper will change color according to the heat of the oven within a few moments.
HEAT DEGREES PAPER TEST
Very hot oven 500 Dark brown
Hot oven 375-400 Light brown
Moderate oven 325-375 yellow
Slow oven 250-325 Crust
TOO BLOODY HOT
Black & on fire!
didn't understand "crust" but the rest made sense just toss in a piece of white paper and give it a few minute and read your results.
Simple and practical
Testing camp oven heats by paper test
Here’s a way to determine the heat of an oven when using coals from a fire.
Pre-heat the oven on a bed of coals. Place a piece of paper inside the oven to find out what heat the oven is at. The paper will change color according to the heat of the oven within a few moments.
HEAT DEGREES PAPER TEST
Very hot oven 500 Dark brown
Hot oven 375-400 Light brown
Moderate oven 325-375 yellow
Slow oven 250-325 Crust
TOO BLOODY HOT
Black & on fire!
didn't understand "crust" but the rest made sense just toss in a piece of white paper and give it a few minute and read your results.