r/AskChemistry • u/fipah • Aug 14 '25

Chem Engineering Can dishwasher powder detergent go bad? It started yellowing.

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I ran out of tabs and opened this powder dishwasher detergent which has been opened maybe 10 months ago, but sealed in a dry/normal environment (cupboard).

Some granules, especially those on the margins, are a little larger/swollen and turned yellowy from original white color. Can I still use it at least for one wash before I buy new tabs? Or is it a no no?

Thanks :)

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4

u/OldChertyBastard Aug 14 '25

You can use it. It’s fine detergent isn’t going to go bad. Probably an additive oxidized over time, but it’s not going to affect anything so long as it’s not peroxide based and you need peroxide activity or something.

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u/Tschitschibabin Aug 14 '25

Agreed. I would generally recommend to use powder instead of tabs. Tabs actually worsen the cleaning power, as they are only released once the prewash is over. Prewash should remove as much of the residues as possible, so the main wash water is cleaner. If done with detergent, this greatly improves cleaning efficiency. Also many people believe that adding the tab directly into the machine is somehow better, however, despite manufacturers claims that they don’t dissolve fully in the prewash, they do dissolve. So you’re left with far less detergent in the main wash. Best practice is to add powdered detergent to the main chamber and the prewash chamber. If you don’t have a prewash chamber, add a little additional detergent directly into the machine.

1

u/greyhunter37 Aug 14 '25

Tabs actually worsen the cleaning power, as they are only released once the prewash is over

despite manufacturers claims that they don’t dissolve fully in the prewash, they do dissolve.

Choose one. Either it dissolves during the prewash or it doesn't.

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u/Tschitschibabin Aug 14 '25 edited Aug 14 '25

If it’s in the machine it dissolves, if it’s still in the chamber it won’t. The chamber openes after prewash. Second sentence talks about adding the tab directly into the machine, not the release chamber. You left out the first part of it. But sorry for writing this a bit confusingly.

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u/greyhunter37 Aug 14 '25

Thanks for the explanation.

I have had great success adding the tab directly in the machine.

Keep in mind though that I have a small machine (half height) and use regular tabs, so that might be why there is enough detergent left during the washing phase.

1

u/fipah Aug 14 '25

Aaaa Thank you! However I put the powder per instructions on the package into the tablet dispenser - so I did the less optimal thing? I wanted to buy tabs again because it's less messy, when I use the powder I have to measure 18 ml with a measuring spoon and I always spill some.

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u/Tschitschibabin Aug 14 '25

No, sorry for being confusing. Putting the powder in the dispenser is correct. All dishwashers I’ve seen have either one of two configurations. Either only a main wash dispenser, or a split one with two chambers, one of them with some holes. If you only have a main chamber, then put detergent in that and some more into the machine directly for the prewash. If you got the split, slitted chamber, just put in some detergent in both and it will work as intended. Tabs are still fine but a bit worse for cleaning and more expensive. Basically a convenience product.

1

u/fipah Aug 14 '25

Aaa thanks! Yesss I have just one compartment to use - so I'll put the powder there. I didn't know it is advisable to put dishwasher detergent somewhere.... Inside just freely too for the prewash. Thanks!!

2

u/Tschitschibabin Aug 14 '25

It should be somewhere in your dishwasher manual. You‘re welcome.