1.   The mixture will bubble and foam when you add the yeast.

2.   Bring to a boil again, stirring occasionally, then reduce heat so mixture bubbles regularly but not furiously.

3.   Bring to a boil, and lower heat so mixture barely bubbles.

4.   Bring to a boil, reduce heat so that mixture bubbles gently, and cover.

5.   Mixture should bubble if yeast is active.

6.   Mixture will bubble up and may spatter.

7.   Mixture will bubble dramatically but eventually subside.

8.   The mixture may bubble up furiously.

9.   The mixture will bubble up and then look creamy.

10.   The mixture should be bubbling gently, not vigorously, whenever you remove the cover.