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Comment by tredre3 | Hacker News Reader

I was with you until you said this:

    > Of all attempts to solve staining from carotenoids (and beta carotene specifically), a quick pre-wash or pre-rinse is the most effective that I know about. Neither heat nor detergent are needed for this, though, because the staining comes from easily rinsable soils, and because heat is actively problematic for this particular type of soil. And for loose soils, temperature and detergent are simply irrelevant.
    > Accordingly, for pre-wash, temperature and detergent are unimportant.

You focus on a very specific type of soil that Technology Connection didn't even mention, and isn't even relevant for a typical wash.

A hot prewash helps loosen fat, that was his claim. Anecdotal experience suggests to me that he's right. So maybe try to disprove that instead?

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> A hot prewash helps loosen fat, that was his claim. Anecdotal experience suggests to me that he's right. So maybe try to disprove that instead?

I don’t know who’s right but the article here already addresses this by pointing out that the short bursts of hot water in a prewash will never have as much impact as the sustained hot water wash in the main cycle.

The author of the post isn’t denying that a hot pre-wash will clean more than a cold pre-wash. What they’re saying is whether the hot pre-wash cleans more than a cold one is irrelevant to the final result since whatever the cold pre-wash doesn’t clean will almost certainly be cleaned in the longer, sustained, hot main cycle.

Hot water is more effective at removing/reducing fat, I think everyone agrees with that. But then the question becomes "Does something get cleaner if you have two hot washes instead of one cold and then one hot?". Personally for me, it feels obvious that if someone doesn't deny "hot water will clean more than a cold water", then they also shouldn't deny "Two hot washes makes something cleaner than one cold and one hot", mainly because that's more hot water, and we already agreed hot water cleans better. The more clean hot water you can apply, the cleaner that thing becomes, I guess would be my conclusion.

Then why not 3 hot washes?

I'm sure there are dishwashers that does 3 cycles, but afaik, most do 2.

That doesn't answer the question.

> You focus on a very specific type of soil that Technology Connection didn't even mention, and isn't even relevant for a typical wash.

But that's a primary issue with TC's tests: it doesn't consider corner cases like this or water hardness. Consumers want it to "just work" and are not going to use a specific settings based on the contents of their dinner.

Sure, it helps the prewash remove fats. But if the main wash and the rinse aid get rid of all that regardless, then it doesn't really matter.

Does it matter if the pre-wash removes 40% of the fat and the main wash removes the last 60% or if instead the pre-wash removed 20% and the main wash removes the last 80%?

Yes, the pre-wash clears away the water from that cycle much faster than the main wash, so the cleaner the main wash water is in the beginning, the more effectively it can clean.

You are describing something like 20% to 95%.

I am talking about 20% to 100%.

a bunch of orange containers/etc that I have beg to differ.

for removing fats and for actual washing there is a main cycle that runs hot

> there is a main cycle that runs hot

This is why you pre-run the hot water in the tap (assuming the dishwasher is attached to the hot water tap/pipe), so the dishwasher has hot water for the pre-wash already. Works for us for a better overall cleaning.

i don't pre-run hot water in the tap. my dishwasher meant to run pre-wash with "whatever" water (and is quoted in article, having hot water in prewash can actually stain things) and it washes everything perfectly. in fact all dishwashers i ever had washed everything fine (as long as they didn't have physical malfunction).

if dishwasher manufacturer thought that prewash needs hot water, it would have heated it to appropriate temperature like it does when it needs to.

Then why don't manufacturers recommend this? Why don't dishwashers in Europe (which have access to higher voltages) run the prewash hotter?

It's because, as outlined in the linked article, hot water makes the problem of staining plastic worse. So they try to mechanically remove it before the main wash. Note that in the original video, the main wash heat temperature wasn't impacted by preheating the prewash.

> Then why don't manufacturers recommend this?

They literally do! https://i.imgur.com/gCDuZZM.png

Rather than jumping into this whole thing in the middle, I'll ask you to begin from the beginning, catch up on what you missed on (the two earlier Technology Connections that were made before the submission article), so we can at least have the same base-level understanding of the situation first, then you can come back and we can argue the entire day.

They literally don't. it's not in my manual and not in manual cheapest LG and GE machines that are currently available for sale

This screenshot is seems to be from manual of Frigidaire FDB520RHB or something similar that was discontinued 12 years ago or so.

Some of the programs of this dishwasher will heat water as needed, and in addition there is a button "hot wash".

showing manual of 20 years old machine today as proof for how machine should be operated it's just like arguing with todays doctor using 300 years old medical books.

things changed.

I have a high end euro-style Bosch, largely seen as one of the best washers out there. No indication in the manual of running hot water. In fact the manual shows the temperatures that all the different cycles run at, and the "pre-rinse" cycle does not show a temperature. The manual also doesn't say to add any detergent other than the main cycle and recommends pacs. Its always at the top of industry testing, so I am thinking a random YouTuber might not be correct here.

It's entirely possible that a cold pre-wash helps avoid staining! But that's not what I'm complaining about.

TC made specific claims about the benefits of a hot pre-wash. Instead of countering those, the blog's author decided to ignore them and build his own strawman to attack.

The author should have refuted the specific claims, or acknowledged them before moving to the drawbacks.

blog author actually discussed it. in form of explaining that hot prewash stains, 85% of cleaning done mechanically, the rest is done with detergent with temperature been supportive (according to published "scientific literature") and that who cares about how things are clean after prewash as long as dishes come out clean after main wash.

in general, it's hilarious. there are literally dozens R&D departments that design dishwashers across dozens of companies. And all of them are wrong because somebody run tests on (checking notes) 30 years old dishwasher.

i trashed dishwasher similar to the one that tests are run on 4 years ago. it was washing everything just fine with exception of few days when check valve broke. after i replaced it, it came back to washing perfectly with cascade platinum pods

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