Science Questions

Why don't my saucepans dry in the dishwasher?

Sun, 17th Feb 2008

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Question

Paul Morgan asked:

Why do my saucepans that I put in my dishwasher never dry properly unlike the plates etcetera? The pans always have water left in them whereas the plates are bone dry. My guess is it’s due to the Teflon® coating keeping the water in large globules.

Answer

When things dry out you’re making the water evaporate and this takes quite a lot of energy.  So you’ve got a large amount of energy in a hot dishwasher, it’s going to be 70, 80, 90 degrees in there.  What you need to do is transfer that heat to the water.  The best way of transferring that heat to the water, is if it’s a thin sheet all over the surface is metal which conducts heat very well.  So most of the heat should evaporate the water and it dries out really well.  Things like china conduct heat reasonably well so if you’ve got hot china it’s got quite a lot of heat in it and it can conduct out well and the water should dry out.  It tends to be in fairly small globules.

As he’s saying Teflon® is very, what’s called, hydrophobic so it doesn’t like water.  The water tends to collect in great big globules so you’ve got to get lots of heat into a very small area which is difficult so heat’s being lost through the rest of the pan.  Also, the Teflon® is quite insulating so it’s hard for heat to get through it.  It will tend to actually go out through the metal on the other side and so probably that’s the reason why you’re getting water left in your pans.

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