I've nerve seen it on glassware though. That warning is usually for plastics since they melt at hot dishwasher water, and on certain metal cook-ware where the caustic dishwasher detergent will corrode the metal anodization, but glass is usually resistant to both temperature and caustic detergents, which is why it's used in bio labs for storing and mixing harsh chemicals, granted, different composition of glass, but it's still glass not adamantium.
So this point doesn't scan for me.
No but the process that strips the paint off delicate crockery is self-evidently abrasive, which stands to reason when you look at the scratch marks in glass that has been through too many cycles.
It's not on glass because an individual washing won't destroy it but repeated washing eventually scratches the glassware to hell. I've seen it with my own eyes.
Marks on glass are not due to abrasion, they appear because glass is slightly soluble in alkaline water, which is the case in dishwashers. Porcelain and stainless steel do not get scratched by dishwashers for example.
I guess that could cause abrasion if there's hard and sharp particles in the water, but I'm not sure what could cause those. Maybe if glass breaks during washing, but I'd assume the machine filters the water before reusing it.
There's a couple of sources:
- The dishwasher tablets have a mildly abrasive substance
- The water itself (especially in the UK) can carry abrasive substances from the pipes
Dishwasher detergent does not contain abrasive substances; dissolve a teaspoon of it in a glass of hot water and see for yourself.
Same substances with different processes produce different results.
That's the key part here. Pubs use commercial dishwashers which effectively shot blast your dishes and glasses. There's a reason you can see "Not dishwasher safe" on certain items: because it'll blast off the nice patterns. I know because I've done it by accident.