One of the final stages of getting a precision flat surface so you can ring two pieces of metal together just by pressing them is lapping compound. I wanted to try toothpaste to see if it could be used instead of lapping compound. I used the toothpaste and rubbed the toothpaste and some water to rub the two surfaces together. To really improve the flatness it would be good to use the toothpaste against a known flat surface. It improve the surface but it didn’t make it flatter.
