Oh, the promise a plastic glass labeled “top rack dishwasher-safe” holds! Carefree kitchens with drinkware that's not only unbreakable, but dishwasher-friendly. No more stacks of plasticware waiting to be hand washed. An escape from tedium… relief from drudgery!
Crystal-clear plastic drinkware unblemished by the dishwasher is certainly a reality for some. But anyone with a dishwasher less than ten years old may hold a different view. Their “top rack dishwasher-safe” tumblers often come out of the top rack crackled, scaly or clouded – sometimes after just a few wash cycles. What gives?
For those quick to point a finger at makers of plastic glasses for mislabeling their products, prepare yourselves. It's not plastic glasses that are faulty – it's that dishwashers have changed greatly in the past decade, mainly due to the EPA's Energy Star guidelines for energy-efficient appliances.
Most dishwashers made prior to 1994 draw hot water directly from a home's water heater, which is usually set at 140-degrees F or so. Though too hot for most household needs, 140-degrees is the optimal cleaning temperature recommended by most dishwasher detergents – and is undamaging to most “top rack dishwasher-safe” plastic drinkware.
Newer Energy Star-rated dishwashers feature built-in water heaters that further heat wash and rinse cycle water by as much as 30-degrees. Since incoming water no longer needs to be quite so hot, home water heaters can be lowered to an energy-saving 115- or 120-degrees, which is fine for other household uses.
Unfortunately, the home's water heater setting is often overlooked when a new dishwasher is installed. And while a 30-degree increase doesn't sound like a lot, it can be enough to breach the heat tolerance of many dishwasher-safe plastics.
But there are ways to enjoy the benefits of newer dishwashers without giving up the convenience of plastic tableware.
Those with Energy Star-rated dishwashers should first check their user manual for wash setting water temperatures. If possible, wash plastic tableware on an unheated setting so incoming hot water will not be overheated. If no unheated option exists, check the home's water heater. If set around 140-degrees, lower it to 120-degrees, so the final water temperature in the dishwasher won't top 150-degrees.
For drying, the air dry setting is generally best to prolong the life of plastic tableware since heated dry temperatures can be excessive for many plastics.
Finally, not all plastics are created equal – some plastics perform much better in all types of dishwashers than others.
For lasting good looks, drinkware and dishes made from resilient plastics like melamine, SAN, polypropylene or polycarbonate are better choices than items labeled “top rack,” which are usually less durable acrylic or polystyrene. Tableware made from these better quality plastics is often found in busy restaurants since it can withstand repeated washings in commercial dishwashers up to 155-degrees.
Best of all, most restaurant-quality plastic tableware is “any rack dishwasher-safe.” Now, that's convenience to sing about.