Do dishwashers really blunt knives
I'm told I should not put sharp knives in the dishwasher because it will blunt them.
What is the mechanism by which this happens or is it a myth?
My take on this:
I have had a 9" Sabatier knife for just over 20 years.
It's been sharpened with a steel whenever it needed it (every few uses) - the steel is now worn out, but the knife *blade* is fine.
However, the overall structure of the knife is a stainless steel blade & tang. It's an encapsulated tang though - the knife tang and end of the blade is wrapped in an aluminium sheath, and that's then inside the black plastic handle.
Because the encapsulating material is aluminimum, the highly caustic dishwasher tablets have eroded it, which means the blade is now slightly loose in the handle.
Since I realised this was happening, I've stopped putting it in the dishwasher, but the damage is done.
However, the dishwasher powder might, since it contains highly alkaline compounds like trisodium phosphate, unless that powder also contains a corrosion inhibitor like sodium silicate.
Although "inhibiting" is not quite the same as "preventing", and so persistent long-term exposure to these chemicals will eventually degrade the materials, including dulling the edge (although that's the least of your concerns, since the rest of the knife is also deteriorating).
This is why professional chefs never put their expensive knives into the dishwasher (indeed they typically don't even trust them to the kitchen porter, but clean them personally).
There is no such thing as a sharp knife. Only a knife which has been sharpened well.
You should re-hone your edge prior to every use (within reason) store the knife well (I use a straw stabby-style knife holder, but magnetic ones are also good.
The edge can be diminished in a dishwasher due to the copious chemical and especially the sodium content, but seriously, if your knife-ware is of such poor quality that it is substantially impacted by this, then you have bought some really criminally poor shit, or you are washing it 12 hours a day every day.
Get a half decent knife sharpener (~£10) and forget about it.
The real questions in the kitchen are to do with quality (or otherwise) pans in the dishwasher. Do some research on Teflon & PFOA. Nice to have, but better to learn to cook properly ;)
Get a half decent knife sharpener (~£10) and forget about it.
Sorry, no. Those half-decent are actually rubbish, because you end up cutting with burrs rather than a honed edge. A standard steel is the best to keep the blade inline and in condition, provided you do it regularly and you use a knife of decent quality steel.
If you want to keep them actually sharp you're stuck with traditional methods, although carborandum stones are no longer necessary (there are diamond stones for the rough-cut start) progressing up to and through the standard oil stone.
Steels are maintenance, they don't sharpen terribly well. That's why butchers hire people to sharpen their knives past a certain point.
And yes, cooking knives in dishwashers tend to be able to bang against other metal objects, resulting in nicks and eventual loss of the edge
you're getting some potentially really bad advice above.
If you knives are stainless steel, dishwasher use may be ok-- in fact, many restaurant grade knives are designed for this. However, some of the best blades are high carbon steel (much sharper). You don't want any water sitting on carbon steel (rusting) and it tends to be more sensitive to chemicals.
Also, would recommend you be careful about sharpening. You don't want to actually do this often, you want to steel your blade at every use and sharpen as needed. Sharpening is a really good way to permanently destroy a blade if you don't know what you're doing and there are lots of cheap and not so cheap sets that will help you with that. In particular, most of the sharpeners that have two carbide bits (sometimes disks, sometimes rods) you pull your blade through and the electric sharpeners are recipes for destroying your edge. I've successfully used and would recommend the Lansky youtube demo here, but in general you shouldn't need to sharpen a lot and if you're about to buy a high-end knife, it should come from the factory with a pretty darn good edge. Read the manual for any sharpener you get carefully before you go and use it. Or, visit your local butcher and find out who they get to sharpen their knives. The key though, is a nice, long, steel (longer is easier to use and less work) with consistent, low pressure strokes.
From my understanding, the alkali used in dishwasher "soap" causes decarburization (or decarbonization) at the knife edge, essentially leaving a rough surface...so not a rust issue, but a lack of sharp edge issue. I think some commercial dishwashers don't even use an alkali, rather high pressure water and steam, thus maybe in commercial world this is not an issue.
In particular, most of the sharpeners that have two carbide bits (sometimes disks, sometimes rods) you pull your blade through and the electric sharpeners are recipes for destroying your edge
Personally I think those things should be flat out banned because they're dangerous. You end up with an edge which consists mainly of burrs. Sure, it'll cut really well afterwards - maybe twice if you're lucky - but you have just made an incredible mess.
Concur 100% with the steel observation - there is no substitute. You can follow up with a belt, but that's for perfectionists or cut throat razors :)
Hmm, whilst I have to agree with some of what HS said, I think that it all depends on the knife.
Prior to using the knife make a test cut, if that isn't clean, then sharpen the knife, this is just basic safety. I have used knives for butchery which have lasted years, being used 5 hours a day and sharpened sometimes twice a day+ especially when bones are involved.
The sharpener you use, if you aren't a knife geek is very important - butt there are plenty of simple ones on the market that do a great and safe job, you are honing, not grinding! A very important difference!
Regarding water / chemical corrosion. Slicing anything will get the knife wet and keep it wet. Slicing something like apples (especially) will pit the metal - high carbon metal very quickly. Many chefs I have talked to actually state that high carbon knives are not sanitary.
Bear in mind, of course, of all the equipment in the kitchen, the knife is amongst the easiest to wipe clean and store dry anyway!
As far as dulling the knife goes, storage and chopping board are just as important as washing.
I like this style of block: http://www.redferret.net/?p=17354 (though there are alo ones with none edge contact slots which are good)
I am happy using this style of sharpener: http://www.lakeland.co.uk/14747/Robert-Welch-Signature-Knife-Sharpener?src=gfeed&gclid=CPKtjZ7uvLoCFWfLtAod-ScAsw
I use Wusthof knives, I have a favourite knife for all prep work and this is this top one: http://www.wusthof.com/desktopdefault.aspx/tabid-75/105_read-950/317_view-121/categories-121/country-gbr/wlang-2/categories-210 - used extensively for many years and in the dishwasher at least 4 times a week probably.
But to answer your question, the mechanism by which this happens is oxidisation. The chemicals in the fruit / dishwasher / vegetables will do several things to increase the rate of corrosion. They help water be attracted to the metal (or rather they attract water full stop), and they help make the water a better conductor so the atoms in the oxidisation process can move more freely - this is a catch 22 style and obviously the most affected part will be the thinnest part, which is the edge.
good points. Ceramic (as used in the sharpener you suggest) is much less likely to screw up a blade than carbide. Personally not a fan of that style sharpener, but maybe because I've seen too many people mess up nice cutlery.
this is what I normally use-- takes and holds a great edge, unquestionably dishwasher friendly, and not at all expensive.
I have used Wusthof and Sabatier knives in other people's kitchens, but they've always been disappointingly dull in comparison to my $20 knife. Which goes to the general point of this discussion that you can have the most expensive and best equipment, but if you don't treat it right it won't perform.
It is indeed much more about what you do with it, rather than quality of your tools.
I worked in a catering shop that did a large range of knives (House of Knives in Petone) when I was at school, so got to see the people buying the full sets of forged Wusthof for looks, as well as lots of actual cooking professionals. Best way to sell someone was to let them chop up some carrots with a good example of each knife type, and let them decide. We also supplied the local catering college, and made sure they got good knives rather than the shit they get palmed off on some others.
Also lots of demonstrating steels and sharpening. Steels is nice and easy, you are drawing the blade across the lines in a smooth cutting motion at a 20 degree angle (roughly a quarter of a right angle) with firm but not hard pressure. The "safe" way is to put a steel vertical point down on a chopping board, and cut down it, so you should not cut anyone. A steel "realigns" the fine edge of the blade, pushing it back into alignment. Sharpening is cutting a new fine edge. You can steel your blade on pretty much any hardish metal, I've used the spine of other knives before in a pinch (and steel worktops, palette knives, pan lids etc)
As far as sharp knives go, proper butchers are the fussiest. It's the literal profit margin. But short of the cleaver and cooks knife, pretty much all butchery knives are flexible. Hence tend to be steeled often and sharpened more than any other knife.
For kitchen work, either a light, narrow high grade stamped steel blade or a more weighty forged blade will suit, depending on your budget and feel. Handle comfort is important. I've had professionals swear by each, the lighter blades need to be steeled or sharpened more often, but are less tiring and cheaper. If you need a single large cooks knife (over 10") then you mainly need the length as leverage, so a $30 Victorinex is as useful as a $400 for splitting pumpkins.
My biggest problem with Wusthof is they started making rolled steel stuff that looks like their forged stuff. I've spent a few thousand hours in kitchens using a Wusthof as my workhorse, with Victorinex for my paring knives.
My last work knife was a 9" Classic that was about 5mm thinner from repeated sharpening, and so the bottom inch or two worked as a cleaver (with a wider edge ground on it), and the rest as a normal knife. I won it in a poker game, and traded it away for bag of weed. That was a proper cooks knife :)
As for not being able to tell the difference, I've always been the one with all the kitchen kit in flats, and after the "knife talk" (I have plenty of normal ones, so the few that I'll get mad if you break I'll highlight, and the others can be wrecked) the flatties will use them. And have strong preferences for the Wusthofs. And when flats have moved on, and we run into each other, they always mention that they missed having sharp knives.
Going back to selling them to people, if they are both sharp, you'll notice the difference with a forged knife over a non forged one. Not one that by itself justifies paying 5-10x the price, but there is. If you can't tell the difference, then either they are blunt, or they are rolled steel Wusthofs. In which case, then there isn't any real difference, apart from the handles.
Dishwashers blunt knives when they get knocked against other things, as well as all the other noted parts. In general, knives need sharpening after a bit of use. At home, the wear on the edge from the dishwasher (assuming it gets washed after making dinner for 4) is probably as much as it gets from cutting things. All in all, probably going to have sweet FA effect on the blade. Handles, maybe a different story. Wood sucks for dishwashers, but is less problematic if ignited.
In terms of bang for your buck, a rolled stainless steel cooks knife (german, french or chinese) with a handle that fits your paw, ditto for a paring knife, is perfect. For a knife that will outlast you, forged ftw. I swore I'd never get a forged paring knife (frippery! It'll get thrown away with the peelings!) but got given one as a gift and use it for everything.
As for high carbon knives, I can't think of anyone who sells them for cookware, other than handmade stuff. You want harder, more brittle for cutting. And if you wanted flexibility, you just make a massively cheaper rolled steel. They have a use (easy to resharpen, hard to snap), but they rust like buggery.
TL, DR: Get Wusthof Classic or Grand Prix forged knives if you can afford it. All good rolled steel knifes are basically equal. Handles are important. Dishwasher safe knives are fine in dishwasher.
My beloved can and does destroy any blade by using carving knives to strip willow, etc. You try to cut anything in our kitchen and it makes no difference if you use the 'sharp' or blunt edge. She also objects if I attempt to re-grind them as they become 'too sharp and dangerous'.
The sharpest knife we have is actually a good quality stainless steel butter knife with a bone handle (which has become dyed pink, goodness only knows how) - somehow it has stood up to punishment the actual chopping, paring etc knives wilt at.
She also objects if I attempt to re-grind them as they become 'too sharp and dangerous'.
If my wife said something like that she would get laughed at and told to think about what she's saying. We've had exchanges like that, going both ways, many times.
Knives are SUPPOSED to be sharp and dangerous. That's why you don't let little kids cut up their own steak. But as was mentioned above a very sharp blade is far less dangerous in the kitchen than a kinda sharp blade.
IMO a blunt knife is more dangerous than a sharp one. With a blunt knife you have to use more force and have less control. But I don't have kids to worry about.
I use a ceramic wheel sharpener with Global knives, the type you put a bit of water in and it works great.
I don't use a dishwasher on them, but when I wash them I NEVER let go of the handle, cos having that blade lurking hidden in the washing up would be stupid.
My ex-wife puts knives in the dishwasher, and hers are always blunt. Mind you, they're crap knives to start with. The other problem is that the knife is always in the dishwasher when you need it.
I've never used a sharpener - the grinding noise as you drag the blade through it sounds too much like damage happening. For the past couple of years I've been using a ceramic "steel" , and I find it much more effective than the steel steel I used before. When I bought my insanely expensive Global knife, I couldn't persuade myself to get an £80 Global ceramic steel as well. I subsequently found a ceramic steel in Ikea, for £10 IIRC. Actually, the top-of-the-range knives I bought in Ikea are pretty good, too, and much cheaper than Global.
@Hungry Sean: "Sabatier" isn't a brand. It used to be a name used indiscriminately by manufacturers in Thiers , the French equivalent of Sheffield, but more recently it just describes any French-style cooking knife, typically with a triangular blade and a black handle.
Never saw the point in Global. Looks cool, average steel quality, no bolster. Handle is OK in normal position, but lack of bolster means (for me anyway) when holding it with the blade in a pinch, the side of my middle finger is against a straight and rather uncomfortable edge. Hardly sold any either, but that's more just bad price point. You could get a forged one for the same price, or comparable one for a quarter of the price.
A steel is a steel. Cheap works just fine :)
Ceramic blades hardly ever get blunt but they are very brittle so it depends what use them for and especially what the chopping surface is like. If you chop quickly, say your slicing carrots, on a hard surface you'll quickly splinter it; on a softer surface you'll get years of use.
If a ceramic knife does need sharpening you can do it with an electric device but much better to take it to a knife shop and let them do it.
A friend uses ceramic knives, and curiosity led me to check the edge with a jeweler's loupe. The wear process was chipping, with still-sharp bits between the chips. Looked to me as if it was turning itself into a serrated knive with a sharp, intermittent edge. I suspect it'll stay super sharp until most of the original edge is gone.
Can anyone who actually knows what they're talking about expand on this?
Note to webmaster: We really need an icon of someone talking through a hat.
I imagine the mechanism is people putting them in the same basket perhaps with other assorted utensils and the water jets simply jostle them all together. They then find the sharpened edge softened by tines, handles and whatnot.
Speaking for myself, I don't put my good knives in the dishwasher for two reasons. First I've had one cut through the plastic basket and get beat up by the spinning whirly-gig underneath and second was me being a bit careless when unloading, and having decided that blade up was better, that left a nice scar on my left index finger. Now I wash, dry and store the sharp knives individually to avoid both problems.
I've noticed corrosion on my V-Sabatier knives since my wife has been putting them in the dishwasher. I can't say if they are getting dulled by the process as she also sharpens them regularly with a grinder. I'm willing to believe stainless is more hygienic, but it won't hold as keen an edge as non-stainless. After sharpening with a pocket whetstone, my sailmaker's knife will cut through eight layers of flax sail cloth without much effort. I can't get the same edge on my rig knife, but then it has to deal with salt water.
The dishwasher powder, and especially the softening salt, promote corrosion. How heavy the corrosion is will depend to some extent on the hardness of the water: harder water needs more softening and more softening will mean more corrosion. There are tabs that you can buy that are designed for use with steel and silver (even more susceptible to corrosion) that I find really* do make a difference and now I only use them when washing knifes or pans.
In general, however, knives are easiest washed by hand. If you do wash them in the dishwasher then use the special tabs, use the shortest, gentlest cycle and take them out and dry them as soon as the cycle has ended.
* I recently bought a pH-meter to help identify the best water filter for the very heavy calcium content in the water here, so I do take these things perhaps a little too seriously.
Since I managed to miss it in my spiel above, you are absolutely correct. High carbon needs more frequent sharpening, but can hold a finer (thus sharper) edge. It's softer, and will also take more abuse before snapping or cracking.
Even if you decide they are too unhygenic for the kitchen, they work great as hunting or butchering knives :)
It's a combination of factors. First and foremost there are corrosive chemicals in your dishwasher. They're not going to hurt most of your dishes, but the edge on a blade is surprisingly delicate (well, most blades anyway). Unless you've got a VERY good knife it's not going to be able to stand up to that. Second, people tend to throw all their silverware, knives included, in one basket. The rub up against each other as the dishwasher runs. Now considering that a glass cutting board can do some serious damage to your blade, imagine what a steel fork will do. Third, the blades don't get dried as quickly in the dishwasher as when they get hand washed. Water isn't good for steel. Even stainless steel can only take so much sitting around in water before it starts to feel the effect.
Dishwashers use cleaning agents that has a grit like component which sandblast the dirt off as much as the detergent dissolving grease and they use a high pressure jet to do it. It's this which dulls the edge of the sharp knives more than the chemicals. Just check plates that have had a life of dishwasher cleaning, there are minute scourings which cut into the glaze which you don't get from hand washing and it also removes patterns/pictures from sand etched glasses.
I find that a diamond coated steel is the best way of keeping a good hone on my knives (as well as not letting others use them!) but you need to be able to keep a constant angle of blade to steel (about 17 degrees) or you are wasting your time. If the diamond-steel is new it cuts metal very fast and the inexperienced can ruin an edge in a couple of strokes but they OK for a regrind; thus I always have two, one new and rough the other old and smooth which is used daily for the touch up.
I never knew what sharp was until I got a Spyderco Sharpmaker set. The stones are excellent, and the base provides a very simple (upright is easy for eye to judge) means of getting the angle right. It takes most of the skill out of the job, but not all of it. It is fairly easy to sharpen a kitchen knife so it will shave arm hairs effortlessly --- but it still requires time, patience and some work. You can use the stones independently of the base to sharpen just about anything ---with as much skill as you can muster--- so this kit does not limit one.
Quick and easy version is my Chef'sChoice 2-stage hand sharpener. No shaving, at least not with my knives, but much much quicker to get to fine-slice-a-ripe-tomato stage. In other words: quick and useful! But also much more aggressive on the knives. I'd like an electric one, but that would be shere luxury for an occasional cook, even one who sharpens the knife almost every time. Chef'sChoice seem to be *the* choice of electric sharpener, unless one moves to workshop kit.
My knives are carbon steel. They get sharp more easily; they get blunt quickly; they stain, and rust if left wet. Do pro cooks still use these things? I doubt it. Stainless knives are so very much better these days than they were decades ago. If I were young, today, in my first home, it would probably be stainless all the way --- with a Chef'sChoice pro 3-stage electric sharpener which does honing and steeling as well as grinding.
But I still would probably not buy a dishwasher. Washing up is just not *that* much hassle. So I wouldn't be asking about putting my knives in one!
Having debated this point with my brother for years (basically I think that dishwashers should do no harm and he does not get his knives even close to it), I came to this topic with high expectations of being able to finally settle the debate. Only to find a really long thread where people mostly expose their cutting preferences. Please, restrict yourselves to the point: is a knife safe in the dishwasher?
There's a lot of good advice and some bad above. That said knives (or any sharp thing) are like women, wine and beer, it's what works for you that really matters. Not what some knob at the cutlery store
sold told you. How you use the sharp thing determines what 'sharp' is, as noted above, there's no such thing as 'sharp' just well done and task appropriate sharpening/honing.
Now for the Big Question: Does a dishwasher dull a blade? The answer is no. However, as others have noted, water/minerals/chemicals inside the dishwasher will have a negative impact on how cleanly you cut your (thing).
The sharp part of any sharp blade is made at the very, very, very edge of the blade and is defined by the angles at which the two sides of the knife intersect. The actual part that does the cutting can be seen under 20x magnification, but everything behind that intersection has no effect on the sharpness of the blade, only how the body of the blade interacts with the material as it follows the sharp edge (again, ideally the blade is purpose designed, ie: bread knife).
As the actual sharp part is very small, it is highly susceptible to mineral deposits and corrosion (even stainless and ceramic) that are not visible to the naked eye. Those deposits most certainly have a negative effect on sharpness but are somewhat intensified because they are carried and deposited as particulates in the steam inside a dishwasher instead of being carried away as they are under running water. The steam deposits a nice even coating of particulates across the entire edge.
Another factor is the 'wire edge' created during most abrasive sharpening processes. A stone or burnisher leaves a teeeeny little piece of metal (or ceramic) just past the actual intersection of the two sides of a blade. It is a function of the sharpening and can not be eliminated in process: Removing it is another step (below). Cheap knives are left with this edge intact intentionally, as it is very sharp but it breaks off easily, which is the leading reason cheap or poorly sharpened knives go dull quickly, this unsupported wire edge breaks off. The act of placing a knife in the dishwasher is almost perfect for breaking this edge off as well, but in this case it's the rack that's doing the damage, not the water itself.
In any case, putting water on knives, of any material, is the main issue and it is only intensified by the dishwasher, but the water itself is the problem.
Lastly, a well sharpened knife will stay that way for many decades of home use with 20 seconds on a leather strop after you sharpen it with a stone, a burnisher or cleaning it. Unless you drop it or
stab someone hit something hard like a bone you don't need aggressive sharpening. All you are doing is removing excess material from the blade and repeatedly creating, and subsequently breaking off in use, a wire edge. A strop cleanly removes that wire edge (as opposed to breaking it off) and keeps the actual intersection of the sides even and clean (sharp). Even the finest diamond hones are too coarse at the microscopic level where a strop works. Additionally, it looks totally badass when you break out an old school strop before you cut into the sacrificial holiday animal and your knives will last exponentially longer. My cooking knives were made for my family by a New Hampshire blacksmith in 1784, they've seen sharpening stones exactly 13 times in all those years and they are unbelievably sharp, just from a good stropping after cleaning and before use. It only takes a few seconds.
OK - you beat me. I'm happy that I have the knives that put my mum through chef school about 30 years ago. When she gave up cooking she passed them to me. I've had them since 2000.
And after that time they are still the sharpest I have ever used, with them being honed on the steel twice a year at most when my mum visits - she can do that far better than I can, and I really believe in knowing what you are good at, and what you should get someone else to do :)
As to topic, I have been told I can put them in a dishwasher by various people, but couldn't bring myself to do it! It's not like they take long to wash by hand (you just have to be careful)
i had 2 roommates that would use my knives and then put them in the dishwasher to wash instead of wiping them down which i was used to doing while chefing my way throughcollege for an it degree. the knives cost quite a bit and i was a little upset that they were put in the dishwasher to clean, especially when i noticed the cracked handles when retrieving them. the care instructions that come with the knives specifically say 'no dishwasher' and now i know why.
the hot/cold, expansion/contraction effect on my henckles professional s series knives caused the black plastic handles to crack on a 10" chef knife and a 4" paring knife. i think this is due to the knives being full tang construction and the plastic handle bits being riveted onto the full tang. the knives were replaced under the lifetime warranty. i've always had my knives professionally sharpened and only use a honing steel on them to straighten the edge out and they were only washed a couple of times in the dishwasher so i can't comment on them being dulled with an automatic wash.
It all comes down to "she who must be obeyed". No more, no less. So, I refrain from putting knives in the dishwasher, and use an oil stone to sharpen them at reasonable intervals. Between that, the steel works well.
Now, for a definitive answer one needs to try to get Mythbusters to do a complete survey on the subject. There ARE lots of variables: Water type, detergent, additives temperature, length of exposure, knife composition, just to name a few.
So, after you pay the Nordstrom's bill, keep them out of the dishwasher. Peace and domestic tranquility will follow.
Yes I saw that program, and as I have a big old waterheater in my house I decided to keep that door locked as I remember my self too well as a teenager. I used to like the Mythbusters but today I get fed up half way through the introduction which seems to become longer and longer. I have had enough of all the shooting, crashing and explosions. Fine that they have not started yet to show us how to make efficient and cheep explosives at home,
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