Wet compost using yeast or lactic fermentation (was Sustainable Slug Beer)

Step 5

Next stage, mold on top and vinegar smell
Well, I came home from work one day and the hay had trapped the CO2 bubbles from the yeast , raised to the surface and pushed the lid off the can. So I put in a large rock on top of the hay to keep it down. I expected it to slowly sink but it did not.
I presumed the slug beer experiment to be a failure at that stage, A day with insects getting in and all sorts of contamination. But might as well let it run its course.
A light mold soon grew on top but the vinegary smell still remained. I will date the pictures later.
See what happens next on the next step.