Eli5: Why do all my cups and glasses have rims on the bottom that collect water in the dishwasher?
In: Other
Not an expert in any of those topics regarding cups, but Id speculate that for the case of pottery, its a product of the manufacturing process. In the production of pottery, a piece of clay is moulded wet, and then dried to set its shape. Due to the existence of gravity, the pottery will have to stand on something and dry that way. Then after drying, they fire the clay to make it water resistant. They will eventually have to scrape or get the dried clay off the thing it was sitting on while drying. If the bottom is flat, this would be problematic but if the surface in contact is a thin ring as opposed to a filled-in circle its easier to be released from the racks.
Plus, if its the same amount of material used, a dome is structurally stronger than a flat slab of material or feature of a design.
Also, most cups from IKEA have a little chip taken out of the rim, to make way for water in the dishwasher!
If it’s flat, there is a chance that if there is water at the bottom of it, the cup would slide.
Have you see before plastic cup with flat bottom? They slide when there are water at the base
The bottom rim helps cups not suction to surfaces under condensation and the air gap in the rim helps insulates your drink better. Some cups have gaps in the bottom rim to let water flow out, some don’t.
Ikea makes cups that have a slit or two on the bottom exactly for this purpose, so the water flows out when upside down
IIRC some cups (pretty sure I saw this on IKEA ones) have a small gap in the rim on the bottom so water can run off
If a perfectly flat cup sat upon a perfectly flat table and any kind of moisture was to develop between the cup and the table be in by condensation or spillage… the cup would stick to the table.
The problem is that you are putting them flat in the dishwasher. Put them on an angle so the water runs off.
Because you’re not tilting all of your mugs and glasses at 45 degrees (preferably so that the opening is facing the center of the washer). Do that, and none of you cups and glasses will have a rim on the bottom that collects water.
Life pro tip. If the water in the rims is bothering you…once the dishwasher finishes all the wash cycles, open the door, drape a tea towel over the it, and reclose your door. The tea towel absorbs the water that is left in the rims.
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