Can dishwashers "crack" glassware and china?

[BristolBoy33]

Please can someone resolve an argument between my wife and I? She says some of our drinking glasses, mugs and cups are cracked because of the dishwasher, and we need a new dishwasher. I say that items in a dishwasher get very hot, and frequent washing in a dishwasher can cause the glaze on porcelain/pottery mugs etc to craze or crack. Drinking glasses seem to develop what look like deep scratches after frequent washing. But surely this is only natural, and is just the price you have to pay for the convenience of using a dishwasher - it does not mean the dishwasher is faulty and needs repairing or replacing?

 

[Burnerman]

Dishwashers have a general wash temperature of 65 degrees and this isn't enough to crack crockery if it is stacked correctly. Expect scratching if glasses touch during the wash cycle, and some metallic paints on crockery may fade after a while.
Check your crockery for dishwasher proof properties before buying it!
John

 

[mattylad]

I have a cupboard full of glasses that are no longer see through because of years in a dishwasher.
Everything inside gets hot, once it's finished its all hot - maybe she is opening the door then?
Best to leave it so the heat dries everything.

 

[foxhole]

Glasses will milk over if you wash at the same time with crockery, glasses require max temp of 55 degrees, so you either wash separately or live with it, dishwasher do not damged crockery provided it certified dishwasher safe.

 

[BristolBoy33]

Thanks everyone - I think we're all agreed that dishwashers don't seriously damage "dishwasher-safe" items if the machine is used correctly. Glasses will cloud if you choose to wash them too hot at same time as crockery, and colours may fade after long-term dishwashing - but all this can be mitigated by the user, or put down to personal choice. Just hoping my wife has now forgotten!!!

 

[ericmark]

Lead crystal as the name suggests has a thin lead coating on the glass, today it will not be lead, but it will still have a coating, the dish washer tablets have chemicals in them that can remove the coating so gives them a whitish tinge, you can use additives to replace the coating.

Glass is not all the same, the coefficient of linear expansion varies, with heat proof glass it is very low, so since it expands so little it will not be shock damaged, however since a dish washer is cold fill and heats the water up slowly they will not get shock damage, glass is never fully solid, Roman windows have been shown to be thicker at bottom where the glass has slowly flowed down the pane, but it is extremely slow.

Heat proof glass will really mess up recycling as it will not mix with the rest, this is why broken glass is not accepted for recycling although rather pointless as it gets broken on the wagon so little chance of sorters getting rid of it.

The glaze on pottery is like a glass coating, so the dish washing tablets can also affect them, however the glaze crazes anyway from the stress of pouring in boiling water, and so all the dish washer really does is remove dirt from the cracks so you can't see it.

So with pottery may as well wash in dish washer, it does make them cleaner, with glass it is better to hand wash, it stops the coating coming off, but it is not the dish washer that causes the coating to come off, but the tablets we use in the dish washer, so a new dishwasher will not help, it may help adding glass washing additives or changing the tablet.

 

[BristolBoy33]

Thanks ericmark, that's a REALLY interesting explanation of the properties of glass and pottery!! Whoever would have thought that glass is never fully solid?