Take the 2-minute tour ×
Seasoned Advice is a question and answer site for professional and amateur chefs. It's 100% free, no registration required.

The instruction manual for some of my kitchen equipment says "Dishwasher safe (top shelf)".

What difference is there between what an object on the top shelf of a dishwasher experiences, and what happens to an object on the bottom shelf?

What are the risks of putting one of these items on the bottom shelf?

share|improve this question
    
Great question. After having seen one of our neighbors putting all their top rack dishwasher safe stuff in the bottom of their dishwasher without incident, we figured it would be reasonably safe to experiment with such since we had the same model. Anecdotally, one place where I've lived in the past, I had a tupperware lid deform/melt from falling into the bottom rack. But with our current dishwasher, even the disposible tupperware seems to survive the bottom rack unscathed....so I've been kind of curious why in some dishwashers, it's fine, but not others. –  Jessica Brown Jun 4 '13 at 22:33
add comment

2 Answers

up vote 17 down vote accepted

In most dishwashers the heating elements are on the bottom only. Lightweight plastic items might melt (soften and distort, not drip away) on the bottom, but they don't mind being in the steamy environment or being sprayed with hot detergent-laced water. They are therefore only dishwasher safe on the top shelf.

I've melted a plastic bowl or two in my time; there is a definite difference between top and bottom.

share|improve this answer
2  
That's definitely true of older dishwashers, however newer ones have a heating element that is designed to make sure that all the water is of an even temperature. With newer washers it's generally ok to put plastics on the top or bottom, as long as they aren't soft plastics. –  GdD May 30 '13 at 13:02
3  
I don't think the problem was ever with the temperature of the water, but rather the hot dry option. My apartment has an old dish washer; if I enable the hot dry option the electric heating element in the bottom glows red hot like the one in an oven. –  Dan Neely May 30 '13 at 14:12
    
Yes, I definitely know from experience that it will melt plastic dishes during drying. –  Petah May 31 '13 at 5:30
add comment

Differences include:

  • higher heat (water's had a chance to air cool before it gets higher up)
  • higher pressure

The pressure isn't as big of a deal typically (it could scrub off some finishes, but generally those items aren't marked as being 'dishwasher safe' at all. But for lighter weight items, it often means that they flip over or get thrown (possibly to the bottom of the dishwasher, where the heaters for drying are).

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.