Why Plastic Doesn't Dry In The Dishwasher

An expert explains.

Have you ever opened up the dishwasher after running a cycle only to see that while your plates are dry and your glasses are sparkling (hopefully), the plastic dishes are still wet? While it’s confusing and a little frustrating, it’s also completely normal. The reason you’re hand-drying your plastic dishes after running them through a full cycle is all thanks to science, specifically, chemistry. 

To get some answers to this perplexing plastic situation, we reached out to Matt Mersch, Director of Engineering for Dishwashers at GE Appliances. Turns out that getting plastic dry has been a “longstanding consumer pain point” that GE Appliances managed to solve with what they call Dry Boost technology in their latest dishwashers. So Mersch is one scientist that recognizes the problem and has a couple of ideas for solutions. 

Dishes in the Dishwasher

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Why Plastic Doesn't Dry

Dishwashers work their drying magic by “providing heat and airflow to the dish surfaces to evaporate clinging moisture,” according to Mersch. While it works well on ceramic, glass, and metal, plastic has a different heat capacity than metal or ceramic, which means it absorbs heat at a different rate. “Plastic has low thermal mass, so holds less of the heat the dishwasher supplies the dishes,” says Mersch. That means the water is less likely to evaporate on plastics. In addition to holding less heat, plastic also has “surface energies that allow larger drops of water to cling to dish surfaces” and plastic dishware like re-usable storage containers, “often have lips or rims that increase and 'puddle' captured water.” In short, plastic and water are a perfect storm in the dishwasher.

Tips To Help Plastic Dry

While GE’s new tech is designed to dry “challenging dishware like plastics,” if you’re not currently in the market to buy a new dishwasher, Mersch has a few recommendations. He suggests loading “problem dishes” at an angle, which should “allow water to shed better and avoid collecting in those water capturing features of the dishware.” If you’ve been skipping the rinse agent in your dishwasher, go pick up a bottle. He recommends adding it to your loads as it “keeps water from clinging to dish surfaces in those larger droplet and allows the water to sheet off the dishes more effectively.” 

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