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Tags dishwasher , pans , anodized

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Old 1st December 2004, 03:35 PM   #1
Darat
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Anodized pans: Why can't I put them in the dishwasher?

Most of my pots and pans and baking ware are "anodized", all of them say they can’t be washed in a dishwasher.

Now these are quite expensive so I'm not willing to risk putting them in to see what will happen, but why if this makes them so tough can’t they stand being washed in a dishwasher? I mean I've plastic tubs that can be washed in a dishwasher.

What goes on in a dishwasher that could harm them but doesn’t affect other pans not anodised?
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Old 1st December 2004, 03:40 PM   #2
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Re: Anodized pans: Why can't I put them in the dishwasher?

Quote:
Originally posted by Darat
Most of my pots and pans and baking ware are "anodized", all of them say they can’t be washed in a dishwasher.

Now these are quite expensive so I'm not willing to risk putting them in to see what will happen, but why if this makes them so tough can’t they stand being washed in a dishwasher? I mean I've plastic tubs that can be washed in a dishwasher.

What goes on in a dishwasher that could harm them but doesn’t affect other pans not anodised?
Alkali in the diswasher soap will attack aluminium surfaces, even anodized ones.
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Old 1st December 2004, 03:52 PM   #3
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Re: Re: Anodized pans: Why can't I put them in the dishwasher?

Quote:
Originally posted by jj
Alkali in the diswasher soap will attack aluminium surfaces, even anodized ones.
is dishwasher soap more alkaline than regular dish (hand wash) soap?

perhaps it's a combination of very high water temp with a higher alkaline soap?
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Old 1st December 2004, 11:55 PM   #4
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Get a gas stove. Buy copper pans. Worth every penny.
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Old 2nd December 2004, 01:55 AM   #5
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Re: Re: Anodized pans: Why can't I put them in the dishwasher?

Quote:
Originally posted by jj
Alkali in the diswasher soap will attack aluminium surfaces, even anodized ones.
I have an aluminium pan that says it is "dishwasher safe"...?
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Old 2nd December 2004, 01:57 AM   #6
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Re: Re: Re: Anodized pans: Why can't I put them in the dishwasher?

Quote:
Originally posted by HarryKeogh
is dishwasher soap more alkaline than regular dish (hand wash) soap?
Probably; this is why it also discolours glasses (admittedly, not all glasses) over time.

Edit to add:
I suspect there's also the elevated temperature issue, and the fact that in a dishwasher items are kept wet (exposed to the soap) for much longer than during hand-washing.

There's probably also an aspect of the manufacturers thinking, "We couldn't be bothered to test this item in dishwashers; it's possibly okay but we're not going to certify it."
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Old 2nd December 2004, 02:50 AM   #7
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Don't tell my wife this, but I've been putting our Anolon anodised pans in the dishwasher for the last six months, with no ill effects. Even the silver handles "Which can turn black in a dishwasher" are fine. Mostly it's just about as easy to clean them in the sink, because they're very non-stick. But parts of the handles are difficult to clean, and I like to shove them in a couple of times a week to keep them sparkly.

Certainly there are a new set of Anolon pans out that are dishwasher safe, and they don't look much different to my eyes.

Caveat: Our water is ultra soft, so we don't add any salt to the dishwasher. Don't know if that makes any difference. YMMV.
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Old 2nd December 2004, 02:56 AM   #8
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Quote:
Originally posted by richardm
Caveat: Our water is ultra soft, so we don't add any salt to the dishwasher. Don't know if that makes any difference. YMMV.
Anyone know what the chemistry here is? I've done a (very) quick Google but can't find anything... adding salt would generally make water harder, wouldn't it? Why would you add salt to hard water? Why would you add it to a dishwasher anyway? Wouldn't it just cause more limescale and reduce the lather?

(Edit to add: the only vague information I've found is "home made cleaner" pages like http://www.cleanuppages.com/clean/homemadecleaners.htm . Is the salt thing a myth?)
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Old 2nd December 2004, 02:58 AM   #9
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Quote:
Originally posted by richardm
Don't tell my wife this, but I've been putting our Anolon anodised pans in the dishwasher for the last six months, with no ill effects.
…snip…
Interesting that's the make of mine and the handles are why I’d want to put them in the dishwasher. However my water is very, very hard (you can write on a blackboard with it) so we sort of use salt with a drop of water added. I wonder if it is the salt then that would cause the damage?
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Old 2nd December 2004, 03:06 AM   #10
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Quote:
Originally posted by Matabiri
Anyone know what the chemistry here is? I've done a (very) quick Google but can't find anything... adding salt would generally make water harder, wouldn't it? Why would you add salt to hard water? Why would you add it to a dishwasher anyway? Wouldn't it just cause more limescale?
Don’t know the chemistry but most dishwashers use a resin water softener that is supposed to exchange the calcium ions in the hard water with sodium ions. The sodium doesn't precipitate out like the calcium does and it doesn’t' form a scum when you add soap to it.
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Old 2nd December 2004, 03:12 AM   #11
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Quote:
Originally posted by Darat
Don’t know the chemistry but most dishwashers use a resin water softener that is supposed to exchange the calcium ions in the hard water with sodium ions. The sodium doesn't precipitate out like the calcium does and it doesn’t' form a scum when you add soap to it.
I've just been doing more reading, and that's basically what's been said - limescale is calcium carbonate; remove the calcium and you don't get it. Calcium is removed by ion exchange with sodium, but this requires the resin softener, as you say. I think the addition of salt refreshes the sodium in the softener. I was confused because I thought people were just adding salt directly to their washes, which I don't think would do anything...

Edit to add: http://chemistry.about.com/cs/howthi.../aa082403a.htm
and
http://www.lenntech.com/water-softener-FAQ.htm
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Old 2nd December 2004, 03:16 AM   #12
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Quote:
Originally posted by Matabiri
Anyone know what the chemistry here is? I've done a (very) quick Google but can't find anything... adding salt would generally make water harder, wouldn't it? Why would you add salt to hard water? Why would you add it to a dishwasher anyway? Wouldn't it just cause more limescale and reduce the lather?
I don't think lather is an issue inside a dishwasher.

I've got the instruction book in front of me here, and it says "The dishwasher is equipped with an automatic softener which uses regenerating salts specially developed for dishwashers to remove hardening substances from the water". It goes on to say that users are asked to take great care to close the salt container after filling, because if detergent or water containing it got in there it would impair operation of the regeneration system, voiding the warranty.

So does that imply that there is something going on other than adding salt to the water? Salt used in a catalyst of some sort? If that's the case then it may make no difference to the pans.

Edited after reading the above posts to say "Ah!".
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Old 2nd December 2004, 03:25 AM   #13
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Quote:
Originally posted by richardm
I don't think lather is an issue inside a dishwasher.
Lather is an issue, in a surfactant sense: the reason very hard waters don't lather is that the dissolved minerals react with the soap (to form scum) and thus prevent it from actually cleaning anything.
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Old 2nd December 2004, 03:57 AM   #14
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Quote:
Originally posted by Matabiri
Lather is an issue, in a surfactant sense: the reason very hard waters don't lather is that the dissolved minerals react with the soap (to form scum) and thus prevent it from actually cleaning anything.
Hmm. I've opened my dishwasher mid-cycle on several occasions and I've never seen any lather in there at all, just lots of hot, drippy water. I always had a suspicion that things you handwash with are very lathery because that's what people expect to see.

I have, however, seen a dishwasher which somebody who couldn't find the tablets had fuelled up with washing up liquid. It was a solid block of foam inside there...

I opened the door and peered inside. Slammed it again sharpish as the wall of foam started to totter towards me...
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Old 2nd December 2004, 04:03 AM   #15
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Quote:
Originally posted by richardm
Hmm. I've opened my dishwasher mid-cycle on several occasions and I've never seen any lather in there at all, just lots of hot, drippy water. I always had a suspicion that things you handwash with are very lathery because that's what people expect to see.
Sorry, probably my fault. I'm using "lather" to mean "soapy mix" rather than "foam".

Dishwasher soap (and machine washing powder) contain anti-foaming agents to prevent the build-up of foam.
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Old 2nd December 2004, 05:23 AM   #16
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I was speaking with my brother (we actually own a company that does aluminum anodizing however we do Type II anodizing not Type III aka hard coat anodizing...and yes, it's a pain to explain what I do for a living at cocktail parties) and he seems to concur with JJ above.

Indeed it has to do with the alkalinity. Machine soap has a higher pH to be able to clean dishes without scrubbing and over time this can etch the aluminum oxide (which is all an anodized coating is) film.
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Old 2nd December 2004, 10:38 AM   #17
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I get the impression that dishwasher detergents contain an abrasive--I think that's why my plastic pot handles have gone dull and why they recommend against putting your fine crystal glassware in the machine. My stuff contains sodium silicate (I wonder if they mean feldspar or some refined product); I'm guessing this is to assist scouring.
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Old 2nd December 2004, 12:52 PM   #18
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Quote:
Originally posted by pupdog
My stuff contains sodium silicate (I wonder if they mean feldspar or some refined product); I'm guessing this is to assist scouring.
How is this for coincidence: I was just looking for a source for sodium silicate (also called water glass) before reading this thread. According to encyclopedia.com, one of it's uses is as a detergent. It's water soluble, so I don't think it is there as a scouring agent.
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Old 4th December 2004, 11:33 AM   #19
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Ah, something different indeed. Perhaps sodium silicate is what the maker calls "Shine Shield(TM)"--which supposedly protects glassware from etching due to the other harsh ingredients in their product. I guess the machine could spray fine grit from the water, food scraps, etc.
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Old 4th December 2004, 12:08 PM   #20
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On the somewhat unrelated subject of lather, my [middle] teenager went to start the dishwasher and found we were out of dishwasher soap. He used regular dishwashing soap instead.

Fun was had by all that evening.
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Old 4th December 2004, 02:06 PM   #21
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Quote:
Originally posted by Rob Lister
On the somewhat unrelated subject of lather, my [middle] teenager went to start the dishwasher and found we were out of dishwasher soap. He used regular dishwashing soap instead.

Fun was had by all that evening.
Oh my ed.

I presume you hit on the wet-dry vac method of coping with all that foam?

That, some cooking oil, and a couple of extra passes fixed it for us once when our rince agent dispenser went whacko.
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Old 4th December 2004, 03:38 PM   #22
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Quote:
Originally posted by jj
Oh my ed.

I presume you hit on the wet-dry vac method of coping with all that foam?

That, some cooking oil, and a couple of extra passes fixed it for us once when our rince agent dispenser went whacko.
No wet-dry vac on hand, sorry to say. Dust-pans and homemade squeegees sufficed.

We made it a family event. We bonded.

Middle teenager learned an important life-lesson.
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Old 4th December 2004, 05:25 PM   #23
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Your sort has dishwashers? When I was a kid, we'd let our pet rat Rodger lick the plates clean and that's sufficient.
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Old 4th December 2004, 08:32 PM   #24
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Re: Re: Re: Anodized pans: Why can't I put them in the dishwasher?

Quote:
Originally posted by HarryKeogh
is dishwasher soap more alkaline than regular dish (hand wash) soap?

perhaps it's a combination of very high water temp with a higher alkaline soap?
Soap is different from dishwasher detergent.

Soap has a hydrophilic alkaline end attached to a hydrophobic fatty end. The hydrophobic end sticks to the grease, and the whole thing is soluble due to the hydrophilic end. It's alkaline, but the alkaline end doesn't react much because it's stuck to the hydrophobic end.

Dishwasher detergent is mostly just alkaline. It makes a kind of soap when it comes into contact with the grease. However, it also can react to make other things when it comes in contact with aluminum or aluminum oxide.
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Old 6th December 2004, 06:06 AM   #25
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A strong caustic soda solution (NaOH) will dissolve aluminium.
Don't know what it does to the anodised coating.

Aluminium is toxic. Anything that removes the oxide layer or any other coating, is a hazard, though the oxide layer reforms very fast.

Anyway. Dishwashers are for effete namby pambies. What's
wrong with a kitchen sink?

When I were a lad...etc....
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Old 6th December 2004, 06:32 AM   #26
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The consensus is that it would be a bad idea to put my pots and pans in the dishwasher. (I really, really hope Mrs RichardM doesn't read this thread.)

And SS - get a dishwasher - I guarantee within 2 weeks you will think it is indispensable and would be willing to sell a kidney on ebay (embossed with an image of the virgin Mary) to buy one if it broke down.
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Old 6th December 2004, 09:45 AM   #27
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Well, as I say there has been nil, none, nada effect on the pans, other than to leave them sparkly clean. So whatever chemistry might going on in there, it doesn't seem to be happening in this case. However, in the interests of not having to explain why either (a) a handle has fallen off (b) the pans that once were a nice grey are now an oxidised aluminium colour or (b) why we're both in hospital suffering from Alzheimer's, I shall probably desist.
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Old 6th December 2004, 10:58 AM   #28
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Re: Re: Re: Re: Anodized pans: Why can't I put them in the dishwasher?

Quote:
Originally posted by epepke
Dishwasher detergent is mostly just alkaline. It makes a kind of soap when it comes into contact with the grease.
Well, yes, bear in mind that fat + strong alkali + heat == soap.

That's basically what dishwasher detergent does to the grease on your dishes, it turns it into soap.
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