# Why does paper dull knives/blades? **URL:** \ **Category:** Factual Questions\ **Created:** [June 17, 2017, 5:07pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218 "2017-06-17T17:07:21Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![ZonexandScout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zonexandscout/32/544_2.png) [@ZonexandScout](https://boards.straightdope.com/u/ZonexandScout)\ **Post date:** [June 17, 2017, 7:58pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/21 "2017-06-17T19:58:38Z")
> [@k9bfriender](#): > > I run a dog grooming salon, and I spend hundreds of dollars a month keeping sharp scissors for my groomers. If I see anyone cutting paper with their scissors, there will be some retraining on proper equipment use going on in fairly short order. (I have two pairs of paper scissors around for the times when paper needs to be cut. > > The point is, is that paper will not dull knives or scissors all that much, but it will dull them. You will not notice the effect if you use these scissors to cut paper all the time, as paper is not that hard to cut. > > But, when you go to cut something else with those scissors, you will notice that they are duller. > > Scissors for things like cutting hair are razor sharp. If you only cut clean hair with those scissors, they will stay that sharp for a good while. > > Cutting other things, like paper or dirty hair with those scissors will dull them significantly faster. You would still be able to use them to cut paper, but their razor edge that is useful for hair will be too dull, and will bend the hair in between the blades rather than cleanly slicing it. > > Also, scissors for hair cutting and other uses that need a razor edge are not cheap. I pay between $200-$500 for a single set of scissors. I paid about $5 for a pack of two paper scissors at office depot. > > Use paper scissors for paper. Use the expensive razor sharp scissors for their intended purpose. I totally agree. Hair is actually a lot easier to cut and, therefore, less dulling. The same applies to a razor. Woe unto the person who uses my (beard) razor to shave his/her legs. But, to get back to basics, the original question was (paraphrased), “Of all things you can cut with a knife, does cutting paper dull them significantly more than the others?” I maintain that the answer is, “No.” ---
**Author:** ![Evan\_Drake](https://avatars.discourse-cdn.com/v4/letter/e/b487fb/32.png) [@Evan\_Drake](https://boards.straightdope.com/u/Evan_Drake)\ **Post date:** [June 17, 2017, 8:10pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/22 "2017-06-17T20:10:31Z")
> [@ZonexandScout](#): > > Yes, coated paper contains clay and some other materials, but I am thinking of basic, standard paper. Cutting sandpaper will also dull knives. The clay in coated paper is extremely fine…much finer than a typical sharpening stone. You might as well argue that cutting coated paper will actually improve the blade. Conversely the internet suggests cutting sandpaper as the prime way to sharpen scissors. **[WikiHow](http://www.wikihow.com/Sharpen-Scissors)** Never sharpened scissors personally, so no idea… ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [June 17, 2017, 8:23pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/23 "2017-06-17T20:23:50Z")
> [@ZonexandScout](#): > > I totally agree. Hair is actually a lot easier to cut and, therefore, less dulling. The same applies to a razor. Woe unto the person who uses my (beard) razor to shave his/her legs. > > But, to get back to basics, the original question was (paraphrased), “Of all things you can cut with a knife, does cutting paper dull them significantly more than the others?” I maintain that the answer is, “No.” Yeah, i got off track talking about scissors. I also have extensive experience with knives, having spent nearly 20 years in kitchens before an abrupt career change. Good kitchen knives are also honed to be razor sharp. When you spend several hours a day cutting things, having a sharp knife makes a huge difference on the wear on your wrist. Using the cheap house knifes was probably going to give me arthritis or carpal tunnel, so I got some wusthofs instead. (You can also create a better presentation with sharp knives, allowing thinner and more accurate cuts.) Foods like meats, fruits, and the “vegetables” that are actually fruits usually contain very little in the way of hard minerals, though actual vegetables (the plant parts of a plant) contain cellulose and other fibrous material that can do a bit more dulling on the blade, but still not that much. Cutting other things, like paper, that has hard minerals in it will dull the blade much faster than meats or fruits. Now, I am sure there are other things you could try to cut that would dull the knife faster, but if the question is simply, will cutting paper dull a knife faster than meats and fruits (and cheese for that matter), then I am pretty sure the answer is “yes”. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [June 17, 2017, 8:27pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/24 "2017-06-17T20:27:07Z")
> [@Evan\_Drake](#): > > Conversely the internet suggests cutting sandpaper as the prime way to sharpen scissors. > > **[WikiHow](http://www.wikihow.com/Sharpen-Scissors)** > > Never sharpened scissors personally, so no idea… Yeah, scissors with a beveled edge that just needs to be put back into hone will find improved cutting after cutting through sandpaper. That is because the sandpaper will remove and burrs or other blemishes along the blade. You would get better improvement from properly honing them, and that technique would utterly destroy good scissors. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [June 17, 2017, 9:26pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/25 "2017-06-17T21:26:33Z")
Re my notes and the notes of others here are certain scenarios where scissors have to be their sharpest to work properly (hair, fine textiles etc) and even a minute step off that level yields unusable scissors other scenarios like cutting copy paper in my example you can keep using “sharp enough” scissors very satisfactorily for years. If you use a pair of “must be sharpest” scissors for paper cutting they will rapidly degrade to “sharp enough for stiff paper” which is useless for hair cutting here the scissor needs to glide through hair very quickly. ---
**Author:** ![Jeff\_Lichtman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jeff_lichtman/32/1531_2.png) [@Jeff\_Lichtman](https://boards.straightdope.com/u/Jeff_Lichtman)\ **Post date:** [June 18, 2017, 12:07am UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/26 "2017-06-18T00:07:41Z")
The answer is that soft materials can erode hard materials. We know that flowing water can erode rock, so why is it a surprise that paper can erode steel? It doesn’t take much to dull a knife. The edge of a sharp knife is very fine—it’s actually the fineness that makes it sharp. Because of this, you don’t have to remove much metal to turn a sharp knife into a dull one. Another thing that causes knives to go dull is for the edge to roll over (rather than for it to be eroded away). This is why steeling a knife keeps it sharp: the steel straightens up the edge. Again, since the edge of a sharp knife is so fine, it doesn’t take much to distort it. The material being cut doesn’t have to be harder than steel for it to roll the edge over. ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [June 18, 2017, 4:51am UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/27 "2017-06-18T04:51:08Z")
I’ll mess with your minds: How is a “sharpening” “steel” used? The steel is that rod you see fine chefs use on a knife just before using it. Different blade designs are used, depending on intended use. I have a pair Barber’s shears (not “scissors”). The instructions with them were quite specific: “Never use these shears for anything but human hair”. The chef’s knives do not dull in the same manner as an axe or common scissors - the edge folds over - the steel is used to push the edge back in place. Using the steel as a sharpening stone will ruin the blade pretty much instantly. Ever see a sign stating “We sharpen knives”? No sharpening stone for them. I have both a guillotine type paper cutter and a rolling paper trimmer. Paper is a special case. I’m guessing the way the fibers will stretch instead of simply shearing into two. ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [June 18, 2017, 9:08pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/28 "2017-06-18T21:08:15Z")
> [@ZonexandScout](#): > > On the other hand, my own sainted mother would chase us around the house if we used her sewing scissors to cut paper. Amusing story there, now we know how you got your shawnee name _runs with scissors_ ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 18, 2017, 10:19pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/29 "2017-06-18T22:19:01Z")
> [@Jeff\_Lichtman](#): > > The answer is that soft materials can erode hard materials. We know that flowing water can erode rock, so why is it a surprise that paper can erode steel? I’ve tried arguing exactly that point here before to no avail. It seems to be the overwhelmingly popular view that if you have two different materials of different hardnesses in contact, the softer one experiences all the wear, and the harder one experiences none at all. (And that the wear exerted by wood upon hardened saw blades is the result of contamination by hard mineral particles - likewise water upon rock, or chemical reaction or process). But it seems entirely reasonable to me that the differential hardness means there should be differential distribution of wear, not just all of the wear falling on the softer material. ---
**Author:** ![Marci\_Al](https://avatars.discourse-cdn.com/v4/letter/m/e47c2d/32.png) [@Marci\_Al](https://boards.straightdope.com/u/Marci_Al)\ **Post date:** [June 18, 2017, 11:12pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/30 "2017-06-18T23:12:48Z")
> [@ZonexandScout](#): > > I’m still going to disagree. The clay is bound into the paper surface, which is being split by the scissors or knife blade to then pass parallel to the blade. The actual edge of the blade is not cleaving the particles. They are much too fine. This is not the same as trying to cut a rock. > > Besides, the purpose of a blade is to cut, get dull, and be resharpened. If you don’t do all three, the purpose is unfulfilled. You’re saying the clay doesn’t help dull the edge? Well it does, along with the paper fiber itself. Do you know what plant fiber is made of? Calcium carbonate, calcium oxide, sometimes a little silica (the ash part after burning.) That will definitely dull steel. And it takes only a little cross-contract with the cutting edge to dull it. The real cutting happens on the first .005 millimeters of the cutting edge. The rest is just side friction. As to our mothers’ insistence that paper will dull scissors faster than cloth, it’s probably not true (my opinion) as they’re made of roughly the same substance minus the clay coat. It’s constancy of use. A housewife doesn’t really cut cloth all day, unless she makes dresses as a business. In which case the scissors will really get dull. I’m into knives so I kinda know how to sharpen scissors. The old rules no longer apply in our house. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [June 19, 2017, 1:01am UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/31 "2017-06-19T01:01:14Z")
> [@ZonexandScout](#): > > “We can see here in this scientifically accurate animation that each paper molecule uses tiny files to dull the knife blade.” > > No, I put this in the “myth” category. Yes, I know that other posters will argue this, but I will stand firm. Cutting ANYTHING tends to dull blades. The softer the material is, the less dulling effect. Remember, printers use (and have used) sliding knife blades to trim bound books and printed materials for hundreds of years. You will not ruin your knife or scissors by cutting paper. > > On the other hand, my own sainted mother would chase us around the house if we used her sewing scissors to cut paper. Most scissors don’t have knife blades. Professionals (including printers) sharpen their knifes as required. And, Your mothers scissors were probably a lot softer than a paper knife. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [June 19, 2017, 1:18am UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/32 "2017-06-19T01:18:01Z")
> [@TriPolar](#): > > I have no idea if paper dulls knives faster than other common substances but I’ll point out that paper cutters and scissor are honed differently than most knives. They have a chisel edge, flat on one side and less taper. Those blades are not meant to flex at all and most knives are. Paper cutters will also be made of harder steel and so are many modern scissors because no lateral force is expected to be exerted on them. Also, scissors will work reasonably well even when not sharp, on many materials, simply by shearing rather than cutting. Scissors don’t work (or don’t work entirely) by simply being two sharp knives working from opposite sides. They work in part by forcing the material in two different directions ie placing it in shear. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 19, 2017, 8:43am UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/33 "2017-06-19T08:43:50Z")
> [@Princhester](#): > > Also, scissors will work reasonably well even when not sharp, on many materials, simply by shearing rather than cutting. Scissors don’t work (or don’t work entirely) by simply being two sharp knives working from opposite sides. They work in part by forcing the material in two different directions ie placing it in shear. Indeed - and in that respect, they function best when the mating faces are a close fit (i.e. either nice and flat, or non-flat, but precisely matching. ---
**Author:** ![Marci\_Al](https://avatars.discourse-cdn.com/v4/letter/m/e47c2d/32.png) [@Marci\_Al](https://boards.straightdope.com/u/Marci_Al)\ **Post date:** [June 19, 2017, 9:25am UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/34 "2017-06-19T09:25:18Z")
As long as they shear against each other throughout the length, they will cut. Explains why pruning shears are often bent. It makes shearing more continuous. Straight blades tend to diverge from each other. Also, whether for scissors, knives, or shears, material that’s softer than the blade steel also causes dullness because they tend to coat or wrap around the very edge of the blade. Relatively easy to fix through a light touch-up by someone who knows blades. ---
**Author:** ![ZonexandScout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zonexandscout/32/544_2.png) [@ZonexandScout](https://boards.straightdope.com/u/ZonexandScout)\ **Post date:** [June 19, 2017, 4:43pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/35 "2017-06-19T16:43:15Z")
Great discussion, but I’ll make this my last post to the thread. IMHO, it is a myth that cutting paper dulls a knife blade significantly more than cutting string, rope, or many other materials. Obviously, cutting anything that is harder is going to dull a blade faster than cutting something that is softer. But paper does not have some magical blade-defeating powers that will ruin your knife the second they touch. Paper is just “stuff,” and cutting “stuff” dulls knives. When I cut paper using a ruler and my knife, the surface I’m cutting ON has a lot more effect than the paper itself. In my experience, many people are told that cutting paper will dull a knife (or a pair of scissors) excessively and so “rules” are put in place to prevent it. Whether they are justifiable rules or not is up for discussion. In my experience working as an electrician who cuts up insulation, copper wire, cardboard, paper, tape, cloth, rope, string, sheetrock, and wood with my Kershaw, cutting paper is the least of my worries. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 19, 2017, 4:48pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/36 "2017-06-19T16:48:19Z")
I’d guess this started from the concept of “Don’t use my knife/scissors that I only cut hair/cloth/meat/whatever with to cut anything else”, and the anything else was usually paper. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [June 19, 2017, 5:14pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/37 "2017-06-19T17:14:34Z")
> [@Jeff\_Lichtman](#): > > The answer is that soft materials can erode hard materials. We know that flowing water can erode rock, so why is it a surprise that paper can erode steel? Flowing water erodes rock as it contains sand, etc- of harder rock. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 19, 2017, 5:26pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/38 "2017-06-19T17:26:20Z")
> [@DrDeth](#): > > Flowing water erodes rock as it contains sand, etc- of harder rock. Or dissolves the rock. Or erodes it through impact, like with falling rain or waterfalls, or splashing, and through pressure to some degree. But without carrying other substances it is a very slow process. The materials carried by water that erode don’t have to be harder than the rock to erode it, but a lot of it will be. Quartz and aluminum oxides are very hard and abundant, and fragile as well so likely to be broken into fine material carried by water. ---
**Author:** ![gigi](https://avatars.discourse-cdn.com/v4/letter/g/a587f6/32.png) [@gigi](https://boards.straightdope.com/u/gigi)\ **Post date:** [June 19, 2017, 7:23pm UTC](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218/39 "2017-06-19T19:23:49Z")
> [@ZonexandScout](#): > > I totally agree. Hair is actually a lot easier to cut and, therefore, less dulling. The same applies to a razor. Woe unto the person who uses my (beard) razor to shave his/her legs. What do you think it being cut when someone shaves their legs?? [Previous page](https://boards.straightdope.com/t/why-does-paper-dull-knives-blades/789218.md?page=1)