Eli5: Why do all my cups and glasses have rims on the bottom that collect water in the dishwasher?

Question

Eli5: Why do all my cups and glasses have rims on the bottom that collect water in the dishwasher?

In: Other

Answer 1

Depending on the material, it also makes the cup more rigid. A plane is easily bent/folded/distorted because every direction can be a fold line. A convex shape doesn’t fold easily, so the shape is sturdier.

Answer 2

A perfectly flat bottom is harder to make and a convex bottom would make for a wobbly glass or cup.

Answer 3

Without a rim they form an even flat surface that could slide more easily if condensation forms beneath it

Answer 4

It helps the cup sit flat on the table, if you made a cup with a perfectly flat bottom it would be much more difficult to get the symmetry right, and with mass produced cups that would almost always result in cups that can’t sit straight on a table and would fall over easily.

Edit: I got an award lol I’m not sure what it means but thanks a lot!