We soaked 5 eggs in vinegar, cola, water, coffee and the final egg was half soaked in coffee and toothpaste.
After 2 days, the eggs in coffee and cola stained the egg shell and stuck to the surface. This bacteria then breaks down the sugar to make acid which can damage teeth.
We found our toothpaste covered egg stained less than the non toothpaste covered egg.
The vinegar completely dissolved the eggshell, leaving just the membrane behind.