Effect of dishwasher on knives, wood, non-stick, etc.

[Fat Guy]

Conventional wisdom says don't put knives, wooden implements or nonstick cookware in the dishwasher.

I put all three in.

I'm wondering: what's the rationale behind dishwasher avoidance? Has it been studied? Am I nuts?

There are some other things: crystal, plastic... I put them all in.

[Anna N]

Conventional wisdom says don't put knives, wooden implements or nonstick cookware in the dishwasher.

I put all three in.

I'm wondering: what's the rationale behind dishwasher avoidance? Has it been studied? Am I nuts?

There are some other things: crystal, plastic... I put them all in.

From experience: Wood will eventually split/splinter.

From common sense - (good) knives will lose their edge from butting against other stuff (unless maybe you have a Miele with the flat cutlery tray).

Non-stick - why waste dishwasher space on something that can usually be wiped out with a paper towel or given a quick rinse.

My take.

[rlummis]

For carbon steel knives, the reasoning is pretty obvious. For older knives, the wooden handles can become damaged by either the bleaching action or prolonged soaking, but I don't think this applies to the modern treated wood handles.

For other types of knives, I've heard two basic explanations:

The blades get knocked around into other utensils and chip.

It's dangerous to unload.

I don't put my knives in the dishwasher, so I have no experience with the first. Most of the people I know who run their knives through the dishwasher don't have very good knives and don't keep them terribly sharp. Also, this would vary depending on how you load them, i.e. whether you throw them in a basket with other tableware or place them in one of the racks.

Anything else I own goes in the dishwasher. The good china and crystal don't get used enough for the abrasive wear of the detergent to be an issue over my lifetime and the breakage rate of hand washing (especially late at night after a festive meal) tends to be higher for me. I don't use non-stick pans, and cast iron and dishwashers are a bad combination.

[mgaretz]

Because, in a dishwasher, the only mechanical action is the turbulence of the water. By itself, that's not enough to clean moderate to heavy soil. So the detergent has to be a lot more harsh to get the dishes clean. It's that extra strong chemical action that can have a negative effect on finishes, wood and knife blades. It may not be apparent even after many washings, but over time it will have an effect.

[kayb]

My plastic cutting boards go in the dishwasher, but not my wooden ones; they will, in fact, eventually split. My paring knives, steak knives, etc., go in the dishwasher, but not my good chef's knives. China, yes. Crystal I don't have, so not an issue. Cookware usually gets handwashed because it takes up too much room in the d/w.

[Shamanjoe]

Alton Brown mentioned that the high heat of the dry cycle can wreak havoc with a lot of the items you're not supposed to stick in the dishwasher, notably wood, cheaper plastic handles, etc..

[tirgoddess]

My chef knives do not go in, I think that the minerals in the water will dull the knives over time (no science, just a hunch). Wood cutting boards do not go in either. We hand wash our silver plate table service which we use daily, the dishwasher was wrecking it even though Kitchenaid says it can go in. Wood handled spreaders and cooking tools go in, no problem so far (4 years). All non stick goes in, it is relatively inexpensive and gets tons of use. We didn't have a dishwasher for 10 years, so we are loving it....

[Shalmanese]

I think the "knives will chip" argument is complete bunk. It's not a goddamn washing machine in there, any movement is going to be minimal at best. And this is for an item who's designed purpose is to impact things with large velocities and force.

There probably are good reasons for not putting good knives in the dishwasher but this seems like a just-so story.

[gfweb]

A sharp knife in the DW will find my finger every time.

[annabelle]

Alton Brown mentioned that the high heat of the dry cycle can wreak havoc with a lot of the items you're not supposed to stick in the dishwasher, notably wood, cheaper plastic handles, etc..

I don't use the dry cycle on my dishwasher. I shut it off when it's done washing and let them air dry. I also don't usually put my good knives, wooden utensiles or pots/pans in the dishwasher unless I'm feeling lazy. Most of us don't own Samurai quality knives so who cares if they go in the dishwaher now and again.

[Hassouni]

Because, in a dishwasher, the only mechanical action is the turbulence of the water. By itself, that's not enough to clean moderate to heavy soil. So the detergent has to be a lot more harsh to get the dishes clean. It's that extra strong chemical action that can have a negative effect on finishes, wood and knife blades. It may not be apparent even after many washings, but over time it will have an effect.

This seems like the most sensible answer I've heard.

[LesleyC]

the rivets that hold the two halves of the handle onto the knife (if you have that style of knife) deteriorate in the dishwasher over time, and eventually the handles won't stay on. It took 13 years of dishwashing for it to happen to mine though, so I suppose it depends on whether you're happy to replace when that happens or not whether they should go in the dishwasher. I do wash mine by hand now, because I was very upset when the last lot 'died'.

I have had a wooden bowl that went in the dishwasher accidentally, and the finish was totally ruined. I do put the wooden spoons and other wooden utensils in though. I don't care what they look like, and replace when necessary.

I do put crystal in, but run it on a special cycle that doesn't get as hot. If I used the crystal daily though, I probably wouldn't because normal glasses do get a bit cloudy after a few years of regular dishwashing and wouldn't want that to happen to the crystal

[ChrisZ]

The knives thing is all about heat. Heating up a sharp knife is the easiest way to make it blunt. When I was 15 my first job was cleaning out the local butchers, which included washing up all their knives. They could tell if I washed them in water that was too hot as all the knives would lose their edge, and they often told me not to wash them in scalding water.

It's worth knowing that dishwashers don't clean by 'scrubbing' dishes in the way you do it yourself in the sink. Dishwashing powder is mostly caustic soda, and dishwashers basically clean by squirting hot caustic soda over everything until the food corrodes off. Anything that reacts with caustic soda, or a basic environment, will not do well in a dishwasher. If you have glasses or crockery that have a gold rim then it will dissolve in a dishwasher. Aluminium reacts with caustic soda, which would be the source of any warnings not to put aluminium in a dishwasher. Some types of plastic will go cloudy.

So basically - dishwashers clean with heat and caustic soda. Anything that doesn't like heat or caustic soda will fare badly in a dishwasher. Knives don't like heat, and a number of metals don't like caustic soda.

[Ashen]

http://zknives.com/knives/kitchen/misc/ … sher.shtml

very interesting link to an explaination on what a dishwasher can do to a good knife just being run through on normal cycles. There is also an explaintion and data on informal experiment they did with a new Wusthof boning knife made of X50CrMoV15 stainless steel. The knife is unused betweeen washing cycles , average of two cycles per week over fourteen weeks. At the end there is rust pitting on the blade.

Great info on why some knives made out of alloys that are considered better quality could fair worse in the dishwasher based on free chromium atom content.

What I took away from it is, if you don't really care about the knife that is being washed, the dishwasher once in awhile is no big deal.

For a knife you really care about there is no short cut for immediate handwashing and drying.

Edited January 2, 2012 by Ashen (log)

[Shalmanese]

The knives thing is all about heat. Heating up a sharp knife is the easiest way to make it blunt. When I was 15 my first job was cleaning out the local butchers, which included washing up all their knives. They could tell if I washed them in water that was too hot as all the knives would lose their edge, and they often told me not to wash them in scalding water.

The caustic soda is plausible but I have a hard time imagining 100C water doing anything significant to the chemistry of steel. Consider that steel pans regularly get heated up to 250C and down again with no apparent change in it's physical characteristics, I can't think of anything that happens to steel at 100C that would affect sharpness.

[dcarch]

When two dissimilar metals are in an electrolytic (acidic or alkaline) solution, galvanic (corrosion) action can occur.

You never know when you might have two dissimilar metal in the dishwasher.

dcarch

[Dakki]

Many (most?) knives have the scales epoxied on, and heat plus humidity will play hell with epoxy.

The dishwasher in my house is named "Dakki."

[sparrowgrass]

Everything goes in the dishwasher except wooden cutting boards and cast iron. I don't have expensive knives, but they are sharp (enough for me, anyhow). I am careful how I place them in the dishwasher--little ones go blade down in the cutlery basket, chef's knives go on the top rack.

My mother, who is living with me now, hasn't learned the blade down rule.

[thock]

Knives will cut the coating on the dishwasher racks and make the racks rust.

[Porthos]

Everything goes in the dishwasher except wooden cutting boards and cast iron. I don't have expensive knives, but they are sharp (enough for me, anyhow).

Also for me: no wooden bowls.

My best chef's knife is 29 years old and the steel still holds a great edge, the rivets are intact, and the wooden handle just needs a bit of oiling once a year or so.

I so rarely (years between uses) use our good crystal that putting it into the dishwasher doesn't phase me one bit - and they are heirloom pieces.

[annabelle]

The useful life of a dishwasher, at least one that is used with some frequency, say once or twice a day, is about 3 years tops. I don't care how much you paid for it or how many whiz-bang features it may have. Rust away.

[rgruby]

A bit off topic but: To rinse or not?

I don't rinse before I put things in.

With a couple exceptions. The main one being rice. I heard that the rice whizzing around in there can pit things.

Good knives and wooden bowls get washed by hand. As do most of the pots and pans - our dishwasher usually does a poor job on them anyways.(Speaking of which, might be time for a new dishwasher here).

Cheers,

Geoff

[sreeb]

When two dissimilar metals are in an electrolytic (acidic or alkaline) solution, galvanic (corrosion) action can occur.

You never know when you might have two dissimilar metal in the dishwasher.

dcarch

You can be certain that the blade is dissimilar to the rivets in your knife. If the rivets were the same, you couldn't crush them to install them. I have seen several knives where the rivets broke the handle as they expanded due to corrosion. Note that stainless is not immune.

Edited January 2, 2012 by sreeb (log)

[Katie Meadow]

I hope I'm not totally misguided in my efforts to make the stuff I own last as long as possible in good condition.

No wood ever goes in our dishwasher. The handles on my knives look decent. My in-laws put all their wooden handled knives and utensils in the dishwasher and they feel unpleasantly rough and look dried out and pale.

In the dishwasher thread it has been observed many times that the life of modern dishwashers is increasingly short. Other than poor quality manufacturing and the use of cheaper materials and planned obsolescence I can't imagine why. So, I try to run the dishwasher in the most economical way possible, meaning as infrequently as I can get away with. Awkward shaped plastic objects, all pots and pans and large mixing bowls get washed by hand to maximize space in the dishwasher. Because dishes can sit unwashed for more than 24 hours, I briefly rinse them before loading. I don't know how necessary this is, but I don't like opening the door and seeing large congealed food stuffs, or smelling them.

I'm guessing that I am not saving money on water use by washing pots and pans by hand, but hopefully I'm extending the life of the machine. Personally I would rather pay the water bill than buy a new dishwasher every three years.

[Norm Matthews]

I found a good looking cast iron skillet in an antique store but it was so gunked up that I would not want to use it -as is- so I ran it through a full cycle in the dishwasher. It came out as bare iron and rusted. If is dishwasher can do that, I expect a putting a non stick skillet in would be somewhat akin to using a sand blaster on it. My wooded utensils are bamboo. They go in the dishwasher all the time and I could not see any negative effect until after about 5 years. Now they look dry and are bleached out.