Plastic cups may get wet inside when washed in a dishwasher due to a phenomenon called "plasticizer migration" or "plasticizer leaching." Plasticizers are additives used in the manufacturing of some plastics to make them more flexible and durable. Over time, these plasticizers can migrate or leach out of the plastic material, especially when exposed to high temperatures and moisture, such as in a dishwasher.
Here are a few reasons why plastic cups may become wet inside the dishwasher:
Condensation: The high heat and steam inside the dishwasher can cause condensation to form on cooler surfaces, including plastic cups. When the hot water comes into contact with the cool plastic cup, it can cause moisture to accumulate on the interior surface.
Poor drying performance: Plastic is not as effective at retaining heat as other materials like glass or ceramics. During the drying phase of the dishwasher cycle, plastic cups may not retain enough heat to evaporate all the moisture from their surfaces. This can result in residual moisture remaining inside the cups.
Water jet force: The powerful water jets in the dishwasher may push water droplets or spray forcefully against the inside of the plastic cups, causing moisture to enter and collect inside.
To mitigate this issue, you can try the following:
Use the dishwasher's drying options: Some dishwashers have specific drying options, such as heat drying or extra drying cycles. Ensure that these options are enabled to maximize the drying performance.
Load the dishwasher properly: Properly space out the plastic cups and avoid overcrowding them to ensure adequate airflow during the drying phase. This can help the cups dry more effectively.
Towel drying: After the dishwasher cycle is complete, you can remove the plastic cups and towel dry them manually to remove any remaining moisture.
Hand washing: If you consistently encounter this problem with plastic cups, you may consider hand washing them instead of using the dishwasher. Hand washing allows you to control the water temperature and avoid the high heat and moisture exposure that can lead to plasticizer migration.
Remember that not all plastic cups are created equal, and some may be more prone to moisture retention than others. Opting for higher-quality plastic cups or using alternative materials like glass or stainless steel may provide better results in terms of drying performance.