Reasons Why Plastic does not Dry in Dishwashers

If you’ve ever loaded your dishwasher with plastic utensils, only to find them still wet and dripping when the cycle is complete, you’re not alone. It’s a common mystery that has left many scratching their heads. Why does plastic never seem to dry properly in the dishwasher? In this expert article, we delve into the science behind this puzzling phenomenon and uncover the reasons behind the persistent moisture on plastic items. Get ready to unravel the mystery and gain insight into how to solve this problem for spotless, dry plasticware.

The Science of Dishwasher Drying

To understand the science behind dishwasher drying, we must delve into the intricate interplay of heat, water, and airflow inside the dishwasher.

  1. Heat and thermal conductivity:
    Dishwashers use heat as a critical element in the drying process. The heating element or a heated rinse aid raises the temperature inside the dishwasher during the drying phase. However, when it comes to plastic items, their lower thermal conductivity becomes a limiting factor. Plastic does not absorb and conduct heat as efficiently as materials such as glass or ceramics. As a result, plastic items take longer to heat up and retain heat for a shorter period of time, resulting in slower and less effective drying.
  2. Surface Tension and Water:
    Surface tension plays an important role in the drying process. Plastic surfaces tend to have a higher surface tension than other materials. This property causes water molecules to form droplets that cling to the surface rather than dispersing and evaporating quickly. The cohesive forces between the water molecules and the plastic surface prevent efficient evaporation, resulting in wet or damp plastic items even after the dishwasher cycle is complete.
  3. Airflow and Evaporation:
    Proper airflow is critical for effective drying. Dishwashers are designed to circulate hot air during the drying cycle to help evaporate water from the surfaces of dishes. However, plastic items, especially those with complex shapes or deep crevices, can impede air circulation. Water droplets tend to accumulate in these areas, increasing drying time as the trapped moisture impedes evaporation.
  4. Design and Placement:
    The design and placement of plastic items in the dishwasher can significantly affect the drying process. Most dishwashers position the heating element at the bottom, which means that plastic items placed on lower racks are further from the direct heat source. As a result, they may not receive enough heat to dry effectively. In addition, plastic items with concave or curved surfaces create pockets where water can collect, hindering air circulation and impeding drying.

Understanding the Role of Design and Placement

The design and placement of plastic items in the dishwasher can also affect drying efficiency. In many dishwashers, the heating element is located at the bottom of the machine. This means that plastic items placed on the bottom racks are further away from the direct heat source, which hinders the drying process.

In addition, plastic items with concave or curved surfaces tend to trap water more effectively. Utensils with deep ridges or bowls with intricate patterns can create pockets where water collects, making it difficult for air to circulate and thoroughly dry the plastic.

Tips for Improving Plastic Drying

While the inherent properties of plastic pose challenges for dishwasher drying, there are several strategies you can use to improve drying efficiency:

  1. Optimal loading: Arrange plastic items to maximize exposure to heat and airflow. Place them on the top racks or near the sides of the dishwasher, where hot air circulates more effectively.
  2. Rinse and towel dry: Rinsing plastic items before loading can help remove excess food particles, reducing the likelihood of water sticking to surfaces. In addition, consider towel-drying plastic items after the dishwasher cycle to remove any remaining moisture.
  3. Use a rinse aid: Use a rinse aid specifically designed for dishwashers. Rinse aids help lower the surface tension of water, making it easier for water to run off plastic items instead of forming droplets.
  4. Lower temperature settings: Experiment with lower temperature settings on your dishwasher. While hotter settings may be necessary for efficient cleaning, reducing the heat during the drying phase can minimize the risk of warping or melting plastic items while still promoting drying.
  5. Hand washing as an alternative: For particularly sensitive or delicate plastic items, consider hand washing as an alternative. Hand drying allows you to control the process more effectively and ensure thorough drying without the limitations imposed by dishwasher dynamics.

Identifying Inadequate Drying of Plastic Items in Your Dishwasher

Several common signs indicate that plastic items are not drying properly in the dishwasher. Here are some telltale signs to look for:

  • Visible water droplets: If you notice water droplets clinging to the surface of plastic items after the dishwasher cycle is complete, this indicates inadequate drying. Droplets may be present on plates, cups, utensils or other plastic items in the dishwasher.
  • Pooled water: Another sign is the presence of pooled water or small pools at the bottom or in crevices of plastic items. This can occur when water collects in areas with concave or curved surfaces, such as bowls or utensils with deep ridges.
  • Moisture or wetness: When you touch or handle plastic items, they may feel damp or wet even after the dishwasher cycle has finished. This moisture may be particularly noticeable on the bottom or inside of plastic containers or cups.
  • Water spots or streaks: Improper drying can leave water marks or streaks on the surface of plastic items. These marks can be visible and can affect the overall appearance and cleanliness of plastic items.
  • Longer drying time: If plastic items consistently take longer to dry than other dishware materials such as glass or ceramic, it indicates that the plastic is not drying properly. You may notice that plastic items remain wet even after other dishes are completely dry.

Keep in mind that these signs may vary depending on the specific dishwasher model, loading techniques, and the plastic items being washed. If you continue to experience these problems, try the tips in the previous answer to improve the drying performance of plastic items in your dishwasher.

The bottom line

While the challenges of drying plastics in the dishwasher can be frustrating, understanding the underlying factors can help you effectively address the issue. By optimizing loading techniques, using rinse aids and adjusting temperature settings, you can improve drying results and say goodbye to wet plasticware. Remember, a little extra care and attention can go a long way in achieving clean and dry plasticware, ensuring a trouble-free and hygienic kitchen experience.


Why does plastic never dry properly in a dishwasher?

Plastic items often struggle to dry properly in the dishwasher due to a combination of factors. First, plastic has a lower thermal conductivity than materials such as glass or ceramic, which means it takes longer to heat up and retains heat for a shorter period of time. This hinders the drying process because plastic items do not absorb and distribute heat as efficiently. Second, plastic surfaces have a higher surface tension, which causes water droplets to cling to the surface instead of dispersing and evaporating quickly. The cohesive forces between water molecules and the plastic surface prevent efficient evaporation, leaving plastic items wet or damp even after the dishwasher cycle is complete. In addition, the design and placement of plastic items in the dishwasher can affect drying efficiency, as items on lower racks can be further from the heat source, while items with concave or curved surfaces can trap water and impede airflow.

Can I improve the drying of plastics by using a higher temperature setting?

While it may be tempting to increase the temperature setting on your dishwasher, it’s not recommended for plastic items. Higher temperatures can cause plastic to warp or even melt. It is best to stick to the manufacturer’s recommended temperature settings and focus on optimizing other factors such as loading techniques and use of rinse aids.

Does plastic type affect drying performance?

Yes, the type of plastic can affect drying performance. Plastics with higher heat resistance tend to dry better than those with lower heat resistance. For example, items made of polypropylene (PP) or polyethylene terephthalate (PET) may dry more effectively than items made of low-density polyethylene (LDPE) or polystyrene (PS).

Are there any dishwasher detergents or additives that can help plastics dry?

Some dishwasher detergents and rinse aids are specifically formulated to improve drying performance. Look for products that claim improved drying or stain resistance on the package. Rinse aids can help reduce surface tension, allowing water to more easily repel from plastic items and promote faster drying.

Can I hand dry plastic items after the dishwasher cycle?

Yes, manually drying plastic items after the dishwasher cycle can help ensure that they are completely dry. Use a clean dishcloth or towel to thoroughly dry plastic items before storing them. This extra step can help eliminate any residual moisture and promote better drying results.

Is it better to hand wash plastic items instead of using a dishwasher?

Hand washing plastic items can be an alternative if you consistently have problems with drying in the dishwasher. Hand drying allows you to control the drying process more effectively, ensuring that plastic items are thoroughly dried before being stored.

Can using the dishwasher’s “heated dry” option improve the drying of plastics?

The heated dry option on dishwashers can help improve drying performance, including for plastic items. This feature uses heated air during the drying cycle to help with evaporation. Keep in mind, however, that it can use more energy, so consider balancing energy efficiency with drying effectiveness based on your needs.