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Why does paper cut so well?
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up vote
72
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Paper is an extremely flexible material, at least when it is under sheet form. It means it will deform significantly according to the pressure applied and it is easy to fold it.
Therefore, it is extremely counter-intuitive that a sheet of paper could cut through human skin and probably through stiffer/harder materials, since when the skin applies a pressure on the paper, one would expect it to fold/bend apart. Yet it is easy to have a severe cut from paper, through both the epidermis and the dermis. How is that possible? Certainly the width of the sheet of paper plays a big role: the smaller it is, the sharpest it is, but also the more flexible it becomes and the less it should sustain an applied pressure without folding apart!
I can think of other materials such as thin plastic films and aluminium foils. My intuition tells the plastic foil would not cut through skin but the Al foil would, although I am not sure since I did not try the experiment. If this hold true, what determines whether a material would be able to cut through skin? A hair for example, which is flexible and thiner than a paper sheet, is unable to cut through the skin... What makes paper stand out? What is so different that makes it a good cutter?
Maybe it has to do with its microscopic properties and that it contains many fibers, but I highly doubt it because the Al foil does not contain these and yet would probably cut as well.
everyday-life material-science
edited 2 days ago
Chair
3,40941632
asked 2 days ago
coniferous_smellerULPBG-W8ZgjR
1,56521135
 |Â
show 10 more comments
up vote
72
down vote
favorite
Paper is an extremely flexible material, at least when it is under sheet form. It means it will deform significantly according to the pressure applied and it is easy to fold it.
Therefore, it is extremely counter-intuitive that a sheet of paper could cut through human skin and probably through stiffer/harder materials, since when the skin applies a pressure on the paper, one would expect it to fold/bend apart. Yet it is easy to have a severe cut from paper, through both the epidermis and the dermis. How is that possible? Certainly the width of the sheet of paper plays a big role: the smaller it is, the sharpest it is, but also the more flexible it becomes and the less it should sustain an applied pressure without folding apart!
I can think of other materials such as thin plastic films and aluminium foils. My intuition tells the plastic foil would not cut through skin but the Al foil would, although I am not sure since I did not try the experiment. If this hold true, what determines whether a material would be able to cut through skin? A hair for example, which is flexible and thiner than a paper sheet, is unable to cut through the skin... What makes paper stand out? What is so different that makes it a good cutter?
Maybe it has to do with its microscopic properties and that it contains many fibers, but I highly doubt it because the Al foil does not contain these and yet would probably cut as well.
everyday-life material-science
edited 2 days ago
Chair
3,40941632
asked 2 days ago
coniferous_smellerULPBG-W8ZgjR
1,56521135
11
Normal Al foil tends to bend rather than cut, but you can get nasty cuts from the super-heavy foil that's used to seal cans, eg of powdered milk.
– PM 2Ring
2 days ago
8
I've had an aluminium foil cut once. It was vicious.
– David Richerby
2 days ago
36
I thought this question was going to be about why it is so easy to cut through paper with scissors. And now I want to know the answer to that question.
– spacetyper
2 days ago
5
Who told you that a hair is unable to cut through skin? I don't recall for sure, but I thought I had experienced that before. However, I do remember that I have been cut by grass, both grass blades (similar to paper), and thin round grassy stalks (when they were firmly rooted and I tried too hard to pull them out).
– Aaron
2 days ago
3
@Aaron I don't know about hair, but Pampas grass in particular is so prone to cutting skin that kids who grew up in parts of Northern California, where it is invasive, call it 'cut-grass.'
– reve_etrange
2 days ago
 |Â
show 10 more comments
up vote
72
down vote
favorite
up vote
72
down vote
favorite
Paper is an extremely flexible material, at least when it is under sheet form. It means it will deform significantly according to the pressure applied and it is easy to fold it.
Therefore, it is extremely counter-intuitive that a sheet of paper could cut through human skin and probably through stiffer/harder materials, since when the skin applies a pressure on the paper, one would expect it to fold/bend apart. Yet it is easy to have a severe cut from paper, through both the epidermis and the dermis. How is that possible? Certainly the width of the sheet of paper plays a big role: the smaller it is, the sharpest it is, but also the more flexible it becomes and the less it should sustain an applied pressure without folding apart!
I can think of other materials such as thin plastic films and aluminium foils. My intuition tells the plastic foil would not cut through skin but the Al foil would, although I am not sure since I did not try the experiment. If this hold true, what determines whether a material would be able to cut through skin? A hair for example, which is flexible and thiner than a paper sheet, is unable to cut through the skin... What makes paper stand out? What is so different that makes it a good cutter?
Maybe it has to do with its microscopic properties and that it contains many fibers, but I highly doubt it because the Al foil does not contain these and yet would probably cut as well.
everyday-life material-science
edited 2 days ago
Chair
3,40941632
asked 2 days ago
coniferous_smellerULPBG-W8ZgjR
1,56521135
Paper is an extremely flexible material, at least when it is under sheet form. It means it will deform significantly according to the pressure applied and it is easy to fold it.
Therefore, it is extremely counter-intuitive that a sheet of paper could cut through human skin and probably through stiffer/harder materials, since when the skin applies a pressure on the paper, one would expect it to fold/bend apart. Yet it is easy to have a severe cut from paper, through both the epidermis and the dermis. How is that possible? Certainly the width of the sheet of paper plays a big role: the smaller it is, the sharpest it is, but also the more flexible it becomes and the less it should sustain an applied pressure without folding apart!
I can think of other materials such as thin plastic films and aluminium foils. My intuition tells the plastic foil would not cut through skin but the Al foil would, although I am not sure since I did not try the experiment. If this hold true, what determines whether a material would be able to cut through skin? A hair for example, which is flexible and thiner than a paper sheet, is unable to cut through the skin... What makes paper stand out? What is so different that makes it a good cutter?
Maybe it has to do with its microscopic properties and that it contains many fibers, but I highly doubt it because the Al foil does not contain these and yet would probably cut as well.
everyday-life material-science
everyday-life material-science
edited 2 days ago
Chair
3,40941632
asked 2 days ago
coniferous_smellerULPBG-W8ZgjR
1,56521135
edited 2 days ago
Chair
3,40941632
asked 2 days ago
coniferous_smellerULPBG-W8ZgjR
1,56521135
edited 2 days ago
Chair
3,40941632
edited 2 days ago
Chair
3,40941632
edited 2 days ago
Chair
3,40941632
3,40941632
asked 2 days ago
coniferous_smellerULPBG-W8ZgjR
1,56521135
asked 2 days ago
coniferous_smellerULPBG-W8ZgjR
1,56521135
asked 2 days ago
coniferous_smellerULPBG-W8ZgjR
1,56521135
1,56521135
11
Normal Al foil tends to bend rather than cut, but you can get nasty cuts from the super-heavy foil that's used to seal cans, eg of powdered milk.
– PM 2Ring
2 days ago
8
I've had an aluminium foil cut once. It was vicious.
– David Richerby
2 days ago
36
I thought this question was going to be about why it is so easy to cut through paper with scissors. And now I want to know the answer to that question.
– spacetyper
2 days ago
5
Who told you that a hair is unable to cut through skin? I don't recall for sure, but I thought I had experienced that before. However, I do remember that I have been cut by grass, both grass blades (similar to paper), and thin round grassy stalks (when they were firmly rooted and I tried too hard to pull them out).
– Aaron
2 days ago
3
@Aaron I don't know about hair, but Pampas grass in particular is so prone to cutting skin that kids who grew up in parts of Northern California, where it is invasive, call it 'cut-grass.'
– reve_etrange
2 days ago
 |Â
show 10 more comments
11
Normal Al foil tends to bend rather than cut, but you can get nasty cuts from the super-heavy foil that's used to seal cans, eg of powdered milk.
– PM 2Ring
2 days ago
8
I've had an aluminium foil cut once. It was vicious.
– David Richerby
2 days ago
36
I thought this question was going to be about why it is so easy to cut through paper with scissors. And now I want to know the answer to that question.
– spacetyper
2 days ago
5
Who told you that a hair is unable to cut through skin? I don't recall for sure, but I thought I had experienced that before. However, I do remember that I have been cut by grass, both grass blades (similar to paper), and thin round grassy stalks (when they were firmly rooted and I tried too hard to pull them out).
– Aaron
2 days ago
3
@Aaron I don't know about hair, but Pampas grass in particular is so prone to cutting skin that kids who grew up in parts of Northern California, where it is invasive, call it 'cut-grass.'
– reve_etrange
2 days ago
11
11
Normal Al foil tends to bend rather than cut, but you can get nasty cuts from the super-heavy foil that's used to seal cans, eg of powdered milk.
– PM 2Ring
2 days ago
Normal Al foil tends to bend rather than cut, but you can get nasty cuts from the super-heavy foil that's used to seal cans, eg of powdered milk.
– PM 2Ring
2 days ago
8
8
I've had an aluminium foil cut once. It was vicious.
– David Richerby
2 days ago
I've had an aluminium foil cut once. It was vicious.
– David Richerby
2 days ago
36
36
I thought this question was going to be about why it is so easy to cut through paper with scissors. And now I want to know the answer to that question.
– spacetyper
2 days ago
I thought this question was going to be about why it is so easy to cut through paper with scissors. And now I want to know the answer to that question.
– spacetyper
2 days ago
5
5
Who told you that a hair is unable to cut through skin? I don't recall for sure, but I thought I had experienced that before. However, I do remember that I have been cut by grass, both grass blades (similar to paper), and thin round grassy stalks (when they were firmly rooted and I tried too hard to pull them out).
– Aaron
2 days ago
Who told you that a hair is unable to cut through skin? I don't recall for sure, but I thought I had experienced that before. However, I do remember that I have been cut by grass, both grass blades (similar to paper), and thin round grassy stalks (when they were firmly rooted and I tried too hard to pull them out).
– Aaron
2 days ago
3
3
@Aaron I don't know about hair, but Pampas grass in particular is so prone to cutting skin that kids who grew up in parts of Northern California, where it is invasive, call it 'cut-grass.'
– reve_etrange
2 days ago
@Aaron I don't know about hair, but Pampas grass in particular is so prone to cutting skin that kids who grew up in parts of Northern California, where it is invasive, call it 'cut-grass.'
– reve_etrange
2 days ago
 |Â
show 10 more comments
5 Answers
5
active
oldest
votes
up vote
94
down vote
Paper, especially freshly cut pieces, appear to have smooth edges. However, its edges are in fact serrated (i.e. having a jagged edge), making it more like a saw than a smooth blade. This enables the paper to tear through the skin fairly easily. The jagged edges greatly reduce contact area, and causes the pressure applied to be rather high. Thus, the skin can be easily punctured, and as the paper moves in a transverse direction, the jagged edge will tear the skin open.
Paper may bend easily, but it very resistant to lateral compression (along its surface). Try squeezing a few sheets of paper in a direction parallel to its surface (preferably by placing them flat on a table and attempting to "compress" it laterally), and you will see what I mean. This is analogous to cutting skin with a metal saw versus a rubber one. The paper is more like a metal one in this case. Paper is rather stiff in short lengths, such as a single piece of paper jutting out from a stack (which is what causes cuts a lot of the time). Most of the time, holding a single large piece of paper and pressing it against your skin won't do much more than bend the paper, but holding it such that only a small length is exposed will make it much harder to bend. The normal force from your skin and the downward force form what is known as a torque couple. There is a certain threshold torque before the paper gives way and bends instead. A shorter length of paper will have a shorter lever arm, which greatly increases the tolerance of the misalignment of the two forces. Holding the paper at a longer length away decreases this threshold (i.e. you have to press down much more precisely over the contact point for the paper to not bend). This is also an important factor in determining whether the paper presses into your skin or simply bends.
Paper is made of cellulose short fibers/pulp, which are attached to each other through hydrogen bonding and possibly a finishing layer. When paper is bent or folded, fibers at the folding line separate and detach, making the paper much weaker. Even if we unfold the folded paper, those detached fibers do not re-attach to each other as before, so the folding line remains as a mechanically weak region and decreasing its stiffness. This is why freshly made, unfolded paper is also more likely to cause cuts.
Lastly, whether a piece of paper cuts skin easily, of course depends on its stiffness. This is why office paper is much more likely to cut you than toilet paper. The paper's density (mass per unit area), also known as grammage, has a direct influence on its stiffness.
answered 2 days ago
user7777777
1,382115
44
This is indeed a good answer, but leaves several questions unanswered. For example, why can't I read this answer without my face twisting and hands clenching?
– maxathousand
2 days ago
16
@maxathousand Because it mentions paper cuts and toilet paper in the same sentence?
– David Richerby
2 days ago
1
And of course flexible things can cut quite well, for instance wire saws like these: en.wikipedia.org/wiki/Wire_saw or the more common ones used for camping.
– jamesqf
2 days ago
1
I'm not sure the fact that the edges are serrated is enough to ensure that paper cuts well. I think it would be nice if you edited your answer with Floris's information that the edges actually contain extra materials that are "hard" and so makes it easy to understand why paper cuts so well. Both of your answers are thus far complementing well each other's.
– coniferous_smellerULPBG-W8ZgjR
yesterday
3
@coniferous_smellerULPBG-W8ZgjR: What make the edges of paper serrated are the very fibers out of which the paper is made of - it has nothing fundamentally to do with filler particles (although they can enhance the sharpness).
– user7777777
9 hours ago
add a comment |Â
up vote
33
down vote
Paper is an extremely flexible material
This is true, but only in one direction at any given time. When you curve paper across a single axis it adds a massive amount of stiffness to the other axis. See SHUKHOV'S HYPERBOLOIDS and how this uses double curvature strengthening. It is best shown in this picture taken from the article.
My guess is that the majority of paper cuts will happen when there is some amount of curvature on the axis that is normal to the cutting edge of the paper. When the curvature is parallel to the cutting edge, the paper will simply bend more.
When paper is used as a disk cutter, as shown in this video provided by sammy gerbil, it is stiffened by centrifugal force from the very high angular speeds of the disk cutter.
So, in summary, paper is good at cutting because its material properties allow it to act stiff (in a given direction), as well as all of the other answers provided such as jagged edges/sawing effect.
answered 2 days ago
josh
44546
5
Also note blades of grass are often curved in the same way!
– reve_etrange
2 days ago
3
I think another way of putting this is that paper is inelastic (has a high modulus). You can bend a sheet of paper out of it's own plane, but you can't stretch or compress it in the direction of that plane. This is why you get the properties described in the article you cited.
– Dave Tweed
yesterday
@DaveTweed that's a nice info. Feel free to edit josh's answer.
– coniferous_smellerULPBG-W8ZgjR
yesterday
sorry but your guess is wrong. the only thing that matters to the cutting effect is the speed and direction of the paper's motion relative the object it is cutting.
– vulcan_
6 hours ago
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up vote
19
down vote
Paper contains filler particles. These are microscopic “knives†- see for example this picture (Precipitated Calcium Carbonate, from this paper)
When paper is freshly cut, such particles (CaCO3, TiO2, ...) are exposed on the edge. They act like any serrated blade, cutting and removing small amounts of material as you slide the edge along a surface (like your finger...). Many of these together can “eat†enough of your skin to make a cut.
answered 2 days ago
Floris
105k11180313
14
Do you have a citation to show it's indeed these fillers that are responsible for the cutting? I don't know much about paper manufacture, but I'd think applications where appearance isn't as important, such as cardboard boxes, would have less filler. Yet some of the worst paper cuts I've had are from boxes.
– Phil Frost
2 days ago
@PhilFrost - it's a fair point. I recall this from materials science lectures in the '80s - before lecture notes were posted online. If I can find something I will add it. The glue (binder) holding paper together also makes the fibers into an effective knife edge; and cardboard has a lot of binder...
– Floris
2 days ago
1
I like this answer because it's the only one so far that mention these extra materials on the edges of the sheet of paper.
– coniferous_smellerULPBG-W8ZgjR
yesterday
1
The materials your mention on the cut edges are from the clay or plastic used to finish some papers, they will not be present on most (cheaper) papers. The cutting effect of paper is more due to it being an extremely thing edge moving fast enough in the direction of the edge to slice through what it hits.
– vulcan_
6 hours ago
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up vote
13
down vote
It's mostly the movement along the paper edge. It results in a sawing effect on your skin.
You can easily try to push on freshly cut paper (without moving along the edge), and it will be nearly impossible to cut yourself. As soon as you move along the edge(don't try this, or try on your own risk), the sawing effect will quickly cut you.
answered 2 days ago
Aganju
391310
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up vote
2
down vote
There are some good answers here already, but there is also some misinformation.
Paper as a material is essentially a fibre composite material .. compressed, felted, fibres bonded by glue, and possibly surface treated to enhance smoothness. It is a very thin sheet with a microscopic saw edge that when constrained against bending and in motion along the edges direction relative to another object can cut soft materials readily.
old paper will cut as readily as new and folding, curving, or any other structural configuration make no contribution to the paper cutting effect. the only thing that mattes is that the edge is thin and moving, relative to the thing being cut.
the extreme example of the paper cutting effect can be seen in this video
https://www.youtube.com/watch?v=eLXHLRa37_g
Mister Maker takes advantage of the stiffening effect of centrifugal force to use paper to slice and dice a variety of materials
answered 5 hours ago
vulcan_
1214
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vulcan_ is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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5 Answers
5
active
oldest
votes
5 Answers
5
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
94
down vote
Paper, especially freshly cut pieces, appear to have smooth edges. However, its edges are in fact serrated (i.e. having a jagged edge), making it more like a saw than a smooth blade. This enables the paper to tear through the skin fairly easily. The jagged edges greatly reduce contact area, and causes the pressure applied to be rather high. Thus, the skin can be easily punctured, and as the paper moves in a transverse direction, the jagged edge will tear the skin open.
Paper may bend easily, but it very resistant to lateral compression (along its surface). Try squeezing a few sheets of paper in a direction parallel to its surface (preferably by placing them flat on a table and attempting to "compress" it laterally), and you will see what I mean. This is analogous to cutting skin with a metal saw versus a rubber one. The paper is more like a metal one in this case. Paper is rather stiff in short lengths, such as a single piece of paper jutting out from a stack (which is what causes cuts a lot of the time). Most of the time, holding a single large piece of paper and pressing it against your skin won't do much more than bend the paper, but holding it such that only a small length is exposed will make it much harder to bend. The normal force from your skin and the downward force form what is known as a torque couple. There is a certain threshold torque before the paper gives way and bends instead. A shorter length of paper will have a shorter lever arm, which greatly increases the tolerance of the misalignment of the two forces. Holding the paper at a longer length away decreases this threshold (i.e. you have to press down much more precisely over the contact point for the paper to not bend). This is also an important factor in determining whether the paper presses into your skin or simply bends.
Paper is made of cellulose short fibers/pulp, which are attached to each other through hydrogen bonding and possibly a finishing layer. When paper is bent or folded, fibers at the folding line separate and detach, making the paper much weaker. Even if we unfold the folded paper, those detached fibers do not re-attach to each other as before, so the folding line remains as a mechanically weak region and decreasing its stiffness. This is why freshly made, unfolded paper is also more likely to cause cuts.
Lastly, whether a piece of paper cuts skin easily, of course depends on its stiffness. This is why office paper is much more likely to cut you than toilet paper. The paper's density (mass per unit area), also known as grammage, has a direct influence on its stiffness.
answered 2 days ago
user7777777
1,382115
44
This is indeed a good answer, but leaves several questions unanswered. For example, why can't I read this answer without my face twisting and hands clenching?
– maxathousand
2 days ago
16
@maxathousand Because it mentions paper cuts and toilet paper in the same sentence?
– David Richerby
2 days ago
1
And of course flexible things can cut quite well, for instance wire saws like these: en.wikipedia.org/wiki/Wire_saw or the more common ones used for camping.
– jamesqf
2 days ago
1
I'm not sure the fact that the edges are serrated is enough to ensure that paper cuts well. I think it would be nice if you edited your answer with Floris's information that the edges actually contain extra materials that are "hard" and so makes it easy to understand why paper cuts so well. Both of your answers are thus far complementing well each other's.
– coniferous_smellerULPBG-W8ZgjR
yesterday
3
@coniferous_smellerULPBG-W8ZgjR: What make the edges of paper serrated are the very fibers out of which the paper is made of - it has nothing fundamentally to do with filler particles (although they can enhance the sharpness).
– user7777777
9 hours ago
add a comment |Â
up vote
94
down vote
Paper, especially freshly cut pieces, appear to have smooth edges. However, its edges are in fact serrated (i.e. having a jagged edge), making it more like a saw than a smooth blade. This enables the paper to tear through the skin fairly easily. The jagged edges greatly reduce contact area, and causes the pressure applied to be rather high. Thus, the skin can be easily punctured, and as the paper moves in a transverse direction, the jagged edge will tear the skin open.
Paper may bend easily, but it very resistant to lateral compression (along its surface). Try squeezing a few sheets of paper in a direction parallel to its surface (preferably by placing them flat on a table and attempting to "compress" it laterally), and you will see what I mean. This is analogous to cutting skin with a metal saw versus a rubber one. The paper is more like a metal one in this case. Paper is rather stiff in short lengths, such as a single piece of paper jutting out from a stack (which is what causes cuts a lot of the time). Most of the time, holding a single large piece of paper and pressing it against your skin won't do much more than bend the paper, but holding it such that only a small length is exposed will make it much harder to bend. The normal force from your skin and the downward force form what is known as a torque couple. There is a certain threshold torque before the paper gives way and bends instead. A shorter length of paper will have a shorter lever arm, which greatly increases the tolerance of the misalignment of the two forces. Holding the paper at a longer length away decreases this threshold (i.e. you have to press down much more precisely over the contact point for the paper to not bend). This is also an important factor in determining whether the paper presses into your skin or simply bends.
Paper is made of cellulose short fibers/pulp, which are attached to each other through hydrogen bonding and possibly a finishing layer. When paper is bent or folded, fibers at the folding line separate and detach, making the paper much weaker. Even if we unfold the folded paper, those detached fibers do not re-attach to each other as before, so the folding line remains as a mechanically weak region and decreasing its stiffness. This is why freshly made, unfolded paper is also more likely to cause cuts.
Lastly, whether a piece of paper cuts skin easily, of course depends on its stiffness. This is why office paper is much more likely to cut you than toilet paper. The paper's density (mass per unit area), also known as grammage, has a direct influence on its stiffness.
answered 2 days ago
user7777777
1,382115
44
This is indeed a good answer, but leaves several questions unanswered. For example, why can't I read this answer without my face twisting and hands clenching?
– maxathousand
2 days ago
16
@maxathousand Because it mentions paper cuts and toilet paper in the same sentence?
– David Richerby
2 days ago
1
And of course flexible things can cut quite well, for instance wire saws like these: en.wikipedia.org/wiki/Wire_saw or the more common ones used for camping.
– jamesqf
2 days ago
1
I'm not sure the fact that the edges are serrated is enough to ensure that paper cuts well. I think it would be nice if you edited your answer with Floris's information that the edges actually contain extra materials that are "hard" and so makes it easy to understand why paper cuts so well. Both of your answers are thus far complementing well each other's.
– coniferous_smellerULPBG-W8ZgjR
yesterday
3
@coniferous_smellerULPBG-W8ZgjR: What make the edges of paper serrated are the very fibers out of which the paper is made of - it has nothing fundamentally to do with filler particles (although they can enhance the sharpness).
– user7777777
9 hours ago
add a comment |Â
up vote
94
down vote
up vote
94
down vote
Paper, especially freshly cut pieces, appear to have smooth edges. However, its edges are in fact serrated (i.e. having a jagged edge), making it more like a saw than a smooth blade. This enables the paper to tear through the skin fairly easily. The jagged edges greatly reduce contact area, and causes the pressure applied to be rather high. Thus, the skin can be easily punctured, and as the paper moves in a transverse direction, the jagged edge will tear the skin open.
Paper may bend easily, but it very resistant to lateral compression (along its surface). Try squeezing a few sheets of paper in a direction parallel to its surface (preferably by placing them flat on a table and attempting to "compress" it laterally), and you will see what I mean. This is analogous to cutting skin with a metal saw versus a rubber one. The paper is more like a metal one in this case. Paper is rather stiff in short lengths, such as a single piece of paper jutting out from a stack (which is what causes cuts a lot of the time). Most of the time, holding a single large piece of paper and pressing it against your skin won't do much more than bend the paper, but holding it such that only a small length is exposed will make it much harder to bend. The normal force from your skin and the downward force form what is known as a torque couple. There is a certain threshold torque before the paper gives way and bends instead. A shorter length of paper will have a shorter lever arm, which greatly increases the tolerance of the misalignment of the two forces. Holding the paper at a longer length away decreases this threshold (i.e. you have to press down much more precisely over the contact point for the paper to not bend). This is also an important factor in determining whether the paper presses into your skin or simply bends.
Paper is made of cellulose short fibers/pulp, which are attached to each other through hydrogen bonding and possibly a finishing layer. When paper is bent or folded, fibers at the folding line separate and detach, making the paper much weaker. Even if we unfold the folded paper, those detached fibers do not re-attach to each other as before, so the folding line remains as a mechanically weak region and decreasing its stiffness. This is why freshly made, unfolded paper is also more likely to cause cuts.
Lastly, whether a piece of paper cuts skin easily, of course depends on its stiffness. This is why office paper is much more likely to cut you than toilet paper. The paper's density (mass per unit area), also known as grammage, has a direct influence on its stiffness.
answered 2 days ago
user7777777
1,382115
Paper, especially freshly cut pieces, appear to have smooth edges. However, its edges are in fact serrated (i.e. having a jagged edge), making it more like a saw than a smooth blade. This enables the paper to tear through the skin fairly easily. The jagged edges greatly reduce contact area, and causes the pressure applied to be rather high. Thus, the skin can be easily punctured, and as the paper moves in a transverse direction, the jagged edge will tear the skin open.
Paper may bend easily, but it very resistant to lateral compression (along its surface). Try squeezing a few sheets of paper in a direction parallel to its surface (preferably by placing them flat on a table and attempting to "compress" it laterally), and you will see what I mean. This is analogous to cutting skin with a metal saw versus a rubber one. The paper is more like a metal one in this case. Paper is rather stiff in short lengths, such as a single piece of paper jutting out from a stack (which is what causes cuts a lot of the time). Most of the time, holding a single large piece of paper and pressing it against your skin won't do much more than bend the paper, but holding it such that only a small length is exposed will make it much harder to bend. The normal force from your skin and the downward force form what is known as a torque couple. There is a certain threshold torque before the paper gives way and bends instead. A shorter length of paper will have a shorter lever arm, which greatly increases the tolerance of the misalignment of the two forces. Holding the paper at a longer length away decreases this threshold (i.e. you have to press down much more precisely over the contact point for the paper to not bend). This is also an important factor in determining whether the paper presses into your skin or simply bends.
Paper is made of cellulose short fibers/pulp, which are attached to each other through hydrogen bonding and possibly a finishing layer. When paper is bent or folded, fibers at the folding line separate and detach, making the paper much weaker. Even if we unfold the folded paper, those detached fibers do not re-attach to each other as before, so the folding line remains as a mechanically weak region and decreasing its stiffness. This is why freshly made, unfolded paper is also more likely to cause cuts.
Lastly, whether a piece of paper cuts skin easily, of course depends on its stiffness. This is why office paper is much more likely to cut you than toilet paper. The paper's density (mass per unit area), also known as grammage, has a direct influence on its stiffness.
answered 2 days ago
user7777777
1,382115
edited 2 days ago
answered 2 days ago
user7777777
1,382115
answered 2 days ago
user7777777
1,382115
answered 2 days ago
user7777777
1,382115
1,382115
44
This is indeed a good answer, but leaves several questions unanswered. For example, why can't I read this answer without my face twisting and hands clenching?
– maxathousand
2 days ago
16
@maxathousand Because it mentions paper cuts and toilet paper in the same sentence?
– David Richerby
2 days ago
1
And of course flexible things can cut quite well, for instance wire saws like these: en.wikipedia.org/wiki/Wire_saw or the more common ones used for camping.
– jamesqf
2 days ago
1
I'm not sure the fact that the edges are serrated is enough to ensure that paper cuts well. I think it would be nice if you edited your answer with Floris's information that the edges actually contain extra materials that are "hard" and so makes it easy to understand why paper cuts so well. Both of your answers are thus far complementing well each other's.
– coniferous_smellerULPBG-W8ZgjR
yesterday
3
@coniferous_smellerULPBG-W8ZgjR: What make the edges of paper serrated are the very fibers out of which the paper is made of - it has nothing fundamentally to do with filler particles (although they can enhance the sharpness).
– user7777777
9 hours ago
add a comment |Â
44
This is indeed a good answer, but leaves several questions unanswered. For example, why can't I read this answer without my face twisting and hands clenching?
– maxathousand
2 days ago
16
@maxathousand Because it mentions paper cuts and toilet paper in the same sentence?
– David Richerby
2 days ago
1
And of course flexible things can cut quite well, for instance wire saws like these: en.wikipedia.org/wiki/Wire_saw or the more common ones used for camping.
– jamesqf
2 days ago
1
I'm not sure the fact that the edges are serrated is enough to ensure that paper cuts well. I think it would be nice if you edited your answer with Floris's information that the edges actually contain extra materials that are "hard" and so makes it easy to understand why paper cuts so well. Both of your answers are thus far complementing well each other's.
– coniferous_smellerULPBG-W8ZgjR
yesterday
3
@coniferous_smellerULPBG-W8ZgjR: What make the edges of paper serrated are the very fibers out of which the paper is made of - it has nothing fundamentally to do with filler particles (although they can enhance the sharpness).
– user7777777
9 hours ago
44
44
This is indeed a good answer, but leaves several questions unanswered. For example, why can't I read this answer without my face twisting and hands clenching?
– maxathousand
2 days ago
This is indeed a good answer, but leaves several questions unanswered. For example, why can't I read this answer without my face twisting and hands clenching?
– maxathousand
2 days ago
16
16
@maxathousand Because it mentions paper cuts and toilet paper in the same sentence?
– David Richerby
2 days ago
@maxathousand Because it mentions paper cuts and toilet paper in the same sentence?
– David Richerby
2 days ago
1
1
And of course flexible things can cut quite well, for instance wire saws like these: en.wikipedia.org/wiki/Wire_saw or the more common ones used for camping.
– jamesqf
2 days ago
And of course flexible things can cut quite well, for instance wire saws like these: en.wikipedia.org/wiki/Wire_saw or the more common ones used for camping.
– jamesqf
2 days ago
1
1
I'm not sure the fact that the edges are serrated is enough to ensure that paper cuts well. I think it would be nice if you edited your answer with Floris's information that the edges actually contain extra materials that are "hard" and so makes it easy to understand why paper cuts so well. Both of your answers are thus far complementing well each other's.
– coniferous_smellerULPBG-W8ZgjR
yesterday
I'm not sure the fact that the edges are serrated is enough to ensure that paper cuts well. I think it would be nice if you edited your answer with Floris's information that the edges actually contain extra materials that are "hard" and so makes it easy to understand why paper cuts so well. Both of your answers are thus far complementing well each other's.
– coniferous_smellerULPBG-W8ZgjR
yesterday
3
3
@coniferous_smellerULPBG-W8ZgjR: What make the edges of paper serrated are the very fibers out of which the paper is made of - it has nothing fundamentally to do with filler particles (although they can enhance the sharpness).
– user7777777
9 hours ago
@coniferous_smellerULPBG-W8ZgjR: What make the edges of paper serrated are the very fibers out of which the paper is made of - it has nothing fundamentally to do with filler particles (although they can enhance the sharpness).
– user7777777
9 hours ago
add a comment |Â
up vote
33
down vote
Paper is an extremely flexible material
This is true, but only in one direction at any given time. When you curve paper across a single axis it adds a massive amount of stiffness to the other axis. See SHUKHOV'S HYPERBOLOIDS and how this uses double curvature strengthening. It is best shown in this picture taken from the article.
My guess is that the majority of paper cuts will happen when there is some amount of curvature on the axis that is normal to the cutting edge of the paper. When the curvature is parallel to the cutting edge, the paper will simply bend more.
When paper is used as a disk cutter, as shown in this video provided by sammy gerbil, it is stiffened by centrifugal force from the very high angular speeds of the disk cutter.
So, in summary, paper is good at cutting because its material properties allow it to act stiff (in a given direction), as well as all of the other answers provided such as jagged edges/sawing effect.
answered 2 days ago
josh
44546
5
Also note blades of grass are often curved in the same way!
– reve_etrange
2 days ago
3
I think another way of putting this is that paper is inelastic (has a high modulus). You can bend a sheet of paper out of it's own plane, but you can't stretch or compress it in the direction of that plane. This is why you get the properties described in the article you cited.
– Dave Tweed
yesterday
@DaveTweed that's a nice info. Feel free to edit josh's answer.
– coniferous_smellerULPBG-W8ZgjR
yesterday
sorry but your guess is wrong. the only thing that matters to the cutting effect is the speed and direction of the paper's motion relative the object it is cutting.
– vulcan_
6 hours ago
add a comment |Â
up vote
33
down vote
Paper is an extremely flexible material
This is true, but only in one direction at any given time. When you curve paper across a single axis it adds a massive amount of stiffness to the other axis. See SHUKHOV'S HYPERBOLOIDS and how this uses double curvature strengthening. It is best shown in this picture taken from the article.
My guess is that the majority of paper cuts will happen when there is some amount of curvature on the axis that is normal to the cutting edge of the paper. When the curvature is parallel to the cutting edge, the paper will simply bend more.
When paper is used as a disk cutter, as shown in this video provided by sammy gerbil, it is stiffened by centrifugal force from the very high angular speeds of the disk cutter.
So, in summary, paper is good at cutting because its material properties allow it to act stiff (in a given direction), as well as all of the other answers provided such as jagged edges/sawing effect.
answered 2 days ago
josh
44546
5
Also note blades of grass are often curved in the same way!
– reve_etrange
2 days ago
3
I think another way of putting this is that paper is inelastic (has a high modulus). You can bend a sheet of paper out of it's own plane, but you can't stretch or compress it in the direction of that plane. This is why you get the properties described in the article you cited.
– Dave Tweed
yesterday
@DaveTweed that's a nice info. Feel free to edit josh's answer.
– coniferous_smellerULPBG-W8ZgjR
yesterday
sorry but your guess is wrong. the only thing that matters to the cutting effect is the speed and direction of the paper's motion relative the object it is cutting.
– vulcan_
6 hours ago
add a comment |Â
up vote
33
down vote
up vote
33
down vote
Paper is an extremely flexible material
This is true, but only in one direction at any given time. When you curve paper across a single axis it adds a massive amount of stiffness to the other axis. See SHUKHOV'S HYPERBOLOIDS and how this uses double curvature strengthening. It is best shown in this picture taken from the article.
My guess is that the majority of paper cuts will happen when there is some amount of curvature on the axis that is normal to the cutting edge of the paper. When the curvature is parallel to the cutting edge, the paper will simply bend more.
When paper is used as a disk cutter, as shown in this video provided by sammy gerbil, it is stiffened by centrifugal force from the very high angular speeds of the disk cutter.
So, in summary, paper is good at cutting because its material properties allow it to act stiff (in a given direction), as well as all of the other answers provided such as jagged edges/sawing effect.
answered 2 days ago
josh
44546
Paper is an extremely flexible material
This is true, but only in one direction at any given time. When you curve paper across a single axis it adds a massive amount of stiffness to the other axis. See SHUKHOV'S HYPERBOLOIDS and how this uses double curvature strengthening. It is best shown in this picture taken from the article.
My guess is that the majority of paper cuts will happen when there is some amount of curvature on the axis that is normal to the cutting edge of the paper. When the curvature is parallel to the cutting edge, the paper will simply bend more.
When paper is used as a disk cutter, as shown in this video provided by sammy gerbil, it is stiffened by centrifugal force from the very high angular speeds of the disk cutter.
So, in summary, paper is good at cutting because its material properties allow it to act stiff (in a given direction), as well as all of the other answers provided such as jagged edges/sawing effect.
answered 2 days ago
josh
44546
answered 2 days ago
josh
44546
answered 2 days ago
josh
44546
answered 2 days ago
josh
44546
44546
5
Also note blades of grass are often curved in the same way!
– reve_etrange
2 days ago
3
I think another way of putting this is that paper is inelastic (has a high modulus). You can bend a sheet of paper out of it's own plane, but you can't stretch or compress it in the direction of that plane. This is why you get the properties described in the article you cited.
– Dave Tweed
yesterday
@DaveTweed that's a nice info. Feel free to edit josh's answer.
– coniferous_smellerULPBG-W8ZgjR
yesterday
sorry but your guess is wrong. the only thing that matters to the cutting effect is the speed and direction of the paper's motion relative the object it is cutting.
– vulcan_
6 hours ago
add a comment |Â
5
Also note blades of grass are often curved in the same way!
– reve_etrange
2 days ago
3
I think another way of putting this is that paper is inelastic (has a high modulus). You can bend a sheet of paper out of it's own plane, but you can't stretch or compress it in the direction of that plane. This is why you get the properties described in the article you cited.
– Dave Tweed
yesterday
@DaveTweed that's a nice info. Feel free to edit josh's answer.
– coniferous_smellerULPBG-W8ZgjR
yesterday
sorry but your guess is wrong. the only thing that matters to the cutting effect is the speed and direction of the paper's motion relative the object it is cutting.
– vulcan_
6 hours ago
5
5
Also note blades of grass are often curved in the same way!
– reve_etrange
2 days ago
Also note blades of grass are often curved in the same way!
– reve_etrange
2 days ago
3
3
I think another way of putting this is that paper is inelastic (has a high modulus). You can bend a sheet of paper out of it's own plane, but you can't stretch or compress it in the direction of that plane. This is why you get the properties described in the article you cited.
– Dave Tweed
yesterday
I think another way of putting this is that paper is inelastic (has a high modulus). You can bend a sheet of paper out of it's own plane, but you can't stretch or compress it in the direction of that plane. This is why you get the properties described in the article you cited.
– Dave Tweed
yesterday
@DaveTweed that's a nice info. Feel free to edit josh's answer.
– coniferous_smellerULPBG-W8ZgjR
yesterday
@DaveTweed that's a nice info. Feel free to edit josh's answer.
– coniferous_smellerULPBG-W8ZgjR
yesterday
sorry but your guess is wrong. the only thing that matters to the cutting effect is the speed and direction of the paper's motion relative the object it is cutting.
– vulcan_
6 hours ago
sorry but your guess is wrong. the only thing that matters to the cutting effect is the speed and direction of the paper's motion relative the object it is cutting.
– vulcan_
6 hours ago
add a comment |Â
up vote
19
down vote
Paper contains filler particles. These are microscopic “knives†- see for example this picture (Precipitated Calcium Carbonate, from this paper)
When paper is freshly cut, such particles (CaCO3, TiO2, ...) are exposed on the edge. They act like any serrated blade, cutting and removing small amounts of material as you slide the edge along a surface (like your finger...). Many of these together can “eat†enough of your skin to make a cut.
answered 2 days ago
Floris
105k11180313
14
Do you have a citation to show it's indeed these fillers that are responsible for the cutting? I don't know much about paper manufacture, but I'd think applications where appearance isn't as important, such as cardboard boxes, would have less filler. Yet some of the worst paper cuts I've had are from boxes.
– Phil Frost
2 days ago
@PhilFrost - it's a fair point. I recall this from materials science lectures in the '80s - before lecture notes were posted online. If I can find something I will add it. The glue (binder) holding paper together also makes the fibers into an effective knife edge; and cardboard has a lot of binder...
– Floris
2 days ago
1
I like this answer because it's the only one so far that mention these extra materials on the edges of the sheet of paper.
– coniferous_smellerULPBG-W8ZgjR
yesterday
1
The materials your mention on the cut edges are from the clay or plastic used to finish some papers, they will not be present on most (cheaper) papers. The cutting effect of paper is more due to it being an extremely thing edge moving fast enough in the direction of the edge to slice through what it hits.
– vulcan_
6 hours ago
add a comment |Â
up vote
19
down vote
Paper contains filler particles. These are microscopic “knives†- see for example this picture (Precipitated Calcium Carbonate, from this paper)
When paper is freshly cut, such particles (CaCO3, TiO2, ...) are exposed on the edge. They act like any serrated blade, cutting and removing small amounts of material as you slide the edge along a surface (like your finger...). Many of these together can “eat†enough of your skin to make a cut.
answered 2 days ago
Floris
105k11180313
14
Do you have a citation to show it's indeed these fillers that are responsible for the cutting? I don't know much about paper manufacture, but I'd think applications where appearance isn't as important, such as cardboard boxes, would have less filler. Yet some of the worst paper cuts I've had are from boxes.
– Phil Frost
2 days ago
@PhilFrost - it's a fair point. I recall this from materials science lectures in the '80s - before lecture notes were posted online. If I can find something I will add it. The glue (binder) holding paper together also makes the fibers into an effective knife edge; and cardboard has a lot of binder...
– Floris
2 days ago
1
I like this answer because it's the only one so far that mention these extra materials on the edges of the sheet of paper.
– coniferous_smellerULPBG-W8ZgjR
yesterday
1
The materials your mention on the cut edges are from the clay or plastic used to finish some papers, they will not be present on most (cheaper) papers. The cutting effect of paper is more due to it being an extremely thing edge moving fast enough in the direction of the edge to slice through what it hits.
– vulcan_
6 hours ago
add a comment |Â
up vote
19
down vote
up vote
19
down vote
Paper contains filler particles. These are microscopic “knives†- see for example this picture (Precipitated Calcium Carbonate, from this paper)
When paper is freshly cut, such particles (CaCO3, TiO2, ...) are exposed on the edge. They act like any serrated blade, cutting and removing small amounts of material as you slide the edge along a surface (like your finger...). Many of these together can “eat†enough of your skin to make a cut.
answered 2 days ago
Floris
105k11180313
Paper contains filler particles. These are microscopic “knives†- see for example this picture (Precipitated Calcium Carbonate, from this paper)
When paper is freshly cut, such particles (CaCO3, TiO2, ...) are exposed on the edge. They act like any serrated blade, cutting and removing small amounts of material as you slide the edge along a surface (like your finger...). Many of these together can “eat†enough of your skin to make a cut.
answered 2 days ago
Floris
105k11180313
answered 2 days ago
Floris
105k11180313
answered 2 days ago
Floris
105k11180313
answered 2 days ago
Floris
105k11180313
105k11180313
14
Do you have a citation to show it's indeed these fillers that are responsible for the cutting? I don't know much about paper manufacture, but I'd think applications where appearance isn't as important, such as cardboard boxes, would have less filler. Yet some of the worst paper cuts I've had are from boxes.
– Phil Frost
2 days ago
@PhilFrost - it's a fair point. I recall this from materials science lectures in the '80s - before lecture notes were posted online. If I can find something I will add it. The glue (binder) holding paper together also makes the fibers into an effective knife edge; and cardboard has a lot of binder...
– Floris
2 days ago
1
I like this answer because it's the only one so far that mention these extra materials on the edges of the sheet of paper.
– coniferous_smellerULPBG-W8ZgjR
yesterday
1
The materials your mention on the cut edges are from the clay or plastic used to finish some papers, they will not be present on most (cheaper) papers. The cutting effect of paper is more due to it being an extremely thing edge moving fast enough in the direction of the edge to slice through what it hits.
– vulcan_
6 hours ago
add a comment |Â
14
Do you have a citation to show it's indeed these fillers that are responsible for the cutting? I don't know much about paper manufacture, but I'd think applications where appearance isn't as important, such as cardboard boxes, would have less filler. Yet some of the worst paper cuts I've had are from boxes.
– Phil Frost
2 days ago
@PhilFrost - it's a fair point. I recall this from materials science lectures in the '80s - before lecture notes were posted online. If I can find something I will add it. The glue (binder) holding paper together also makes the fibers into an effective knife edge; and cardboard has a lot of binder...
– Floris
2 days ago
1
I like this answer because it's the only one so far that mention these extra materials on the edges of the sheet of paper.
– coniferous_smellerULPBG-W8ZgjR
yesterday
1
The materials your mention on the cut edges are from the clay or plastic used to finish some papers, they will not be present on most (cheaper) papers. The cutting effect of paper is more due to it being an extremely thing edge moving fast enough in the direction of the edge to slice through what it hits.
– vulcan_
6 hours ago
14
14
Do you have a citation to show it's indeed these fillers that are responsible for the cutting? I don't know much about paper manufacture, but I'd think applications where appearance isn't as important, such as cardboard boxes, would have less filler. Yet some of the worst paper cuts I've had are from boxes.
– Phil Frost
2 days ago
Do you have a citation to show it's indeed these fillers that are responsible for the cutting? I don't know much about paper manufacture, but I'd think applications where appearance isn't as important, such as cardboard boxes, would have less filler. Yet some of the worst paper cuts I've had are from boxes.
– Phil Frost
2 days ago
@PhilFrost - it's a fair point. I recall this from materials science lectures in the '80s - before lecture notes were posted online. If I can find something I will add it. The glue (binder) holding paper together also makes the fibers into an effective knife edge; and cardboard has a lot of binder...
– Floris
2 days ago
@PhilFrost - it's a fair point. I recall this from materials science lectures in the '80s - before lecture notes were posted online. If I can find something I will add it. The glue (binder) holding paper together also makes the fibers into an effective knife edge; and cardboard has a lot of binder...
– Floris
2 days ago
1
1
I like this answer because it's the only one so far that mention these extra materials on the edges of the sheet of paper.
– coniferous_smellerULPBG-W8ZgjR
yesterday
I like this answer because it's the only one so far that mention these extra materials on the edges of the sheet of paper.
– coniferous_smellerULPBG-W8ZgjR
yesterday
1
1
The materials your mention on the cut edges are from the clay or plastic used to finish some papers, they will not be present on most (cheaper) papers. The cutting effect of paper is more due to it being an extremely thing edge moving fast enough in the direction of the edge to slice through what it hits.
– vulcan_
6 hours ago
The materials your mention on the cut edges are from the clay or plastic used to finish some papers, they will not be present on most (cheaper) papers. The cutting effect of paper is more due to it being an extremely thing edge moving fast enough in the direction of the edge to slice through what it hits.
– vulcan_
6 hours ago
add a comment |Â
up vote
13
down vote
It's mostly the movement along the paper edge. It results in a sawing effect on your skin.
You can easily try to push on freshly cut paper (without moving along the edge), and it will be nearly impossible to cut yourself. As soon as you move along the edge(don't try this, or try on your own risk), the sawing effect will quickly cut you.
answered 2 days ago
Aganju
391310
add a comment |Â
up vote
13
down vote
It's mostly the movement along the paper edge. It results in a sawing effect on your skin.
You can easily try to push on freshly cut paper (without moving along the edge), and it will be nearly impossible to cut yourself. As soon as you move along the edge(don't try this, or try on your own risk), the sawing effect will quickly cut you.
answered 2 days ago
Aganju
391310
add a comment |Â
up vote
13
down vote
up vote
13
down vote
It's mostly the movement along the paper edge. It results in a sawing effect on your skin.
You can easily try to push on freshly cut paper (without moving along the edge), and it will be nearly impossible to cut yourself. As soon as you move along the edge(don't try this, or try on your own risk), the sawing effect will quickly cut you.
answered 2 days ago
Aganju
391310
It's mostly the movement along the paper edge. It results in a sawing effect on your skin.
You can easily try to push on freshly cut paper (without moving along the edge), and it will be nearly impossible to cut yourself. As soon as you move along the edge(don't try this, or try on your own risk), the sawing effect will quickly cut you.
answered 2 days ago
Aganju
391310
answered 2 days ago
Aganju
391310
answered 2 days ago
Aganju
391310
answered 2 days ago
Aganju
391310
391310
add a comment |Â
add a comment |Â
up vote
2
down vote
There are some good answers here already, but there is also some misinformation.
Paper as a material is essentially a fibre composite material .. compressed, felted, fibres bonded by glue, and possibly surface treated to enhance smoothness. It is a very thin sheet with a microscopic saw edge that when constrained against bending and in motion along the edges direction relative to another object can cut soft materials readily.
old paper will cut as readily as new and folding, curving, or any other structural configuration make no contribution to the paper cutting effect. the only thing that mattes is that the edge is thin and moving, relative to the thing being cut.
the extreme example of the paper cutting effect can be seen in this video
https://www.youtube.com/watch?v=eLXHLRa37_g
Mister Maker takes advantage of the stiffening effect of centrifugal force to use paper to slice and dice a variety of materials
answered 5 hours ago
vulcan_
1214
New contributor
vulcan_ is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |Â
up vote
2
down vote
There are some good answers here already, but there is also some misinformation.
Paper as a material is essentially a fibre composite material .. compressed, felted, fibres bonded by glue, and possibly surface treated to enhance smoothness. It is a very thin sheet with a microscopic saw edge that when constrained against bending and in motion along the edges direction relative to another object can cut soft materials readily.
old paper will cut as readily as new and folding, curving, or any other structural configuration make no contribution to the paper cutting effect. the only thing that mattes is that the edge is thin and moving, relative to the thing being cut.
the extreme example of the paper cutting effect can be seen in this video
https://www.youtube.com/watch?v=eLXHLRa37_g
Mister Maker takes advantage of the stiffening effect of centrifugal force to use paper to slice and dice a variety of materials
answered 5 hours ago
vulcan_
1214
New contributor
vulcan_ is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |Â
up vote
2
down vote
up vote
2
down vote
There are some good answers here already, but there is also some misinformation.
Paper as a material is essentially a fibre composite material .. compressed, felted, fibres bonded by glue, and possibly surface treated to enhance smoothness. It is a very thin sheet with a microscopic saw edge that when constrained against bending and in motion along the edges direction relative to another object can cut soft materials readily.
old paper will cut as readily as new and folding, curving, or any other structural configuration make no contribution to the paper cutting effect. the only thing that mattes is that the edge is thin and moving, relative to the thing being cut.
the extreme example of the paper cutting effect can be seen in this video
https://www.youtube.com/watch?v=eLXHLRa37_g
Mister Maker takes advantage of the stiffening effect of centrifugal force to use paper to slice and dice a variety of materials
answered 5 hours ago
vulcan_
1214
New contributor
vulcan_ is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
There are some good answers here already, but there is also some misinformation.
Paper as a material is essentially a fibre composite material .. compressed, felted, fibres bonded by glue, and possibly surface treated to enhance smoothness. It is a very thin sheet with a microscopic saw edge that when constrained against bending and in motion along the edges direction relative to another object can cut soft materials readily.
old paper will cut as readily as new and folding, curving, or any other structural configuration make no contribution to the paper cutting effect. the only thing that mattes is that the edge is thin and moving, relative to the thing being cut.
the extreme example of the paper cutting effect can be seen in this video
https://www.youtube.com/watch?v=eLXHLRa37_g
Mister Maker takes advantage of the stiffening effect of centrifugal force to use paper to slice and dice a variety of materials
answered 5 hours ago
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answered 5 hours ago
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11
Normal Al foil tends to bend rather than cut, but you can get nasty cuts from the super-heavy foil that's used to seal cans, eg of powdered milk.
– PM 2Ring
2 days ago
8
I've had an aluminium foil cut once. It was vicious.
– David Richerby
2 days ago
36
I thought this question was going to be about why it is so easy to cut through paper with scissors. And now I want to know the answer to that question.
– spacetyper
2 days ago
5
Who told you that a hair is unable to cut through skin? I don't recall for sure, but I thought I had experienced that before. However, I do remember that I have been cut by grass, both grass blades (similar to paper), and thin round grassy stalks (when they were firmly rooted and I tried too hard to pull them out).
– Aaron
2 days ago
3
@Aaron I don't know about hair, but Pampas grass in particular is so prone to cutting skin that kids who grew up in parts of Northern California, where it is invasive, call it 'cut-grass.'
– reve_etrange
2 days ago