The Naked Scientists

The Naked Scientists Forum

Author Topic: why does ribbon curl up when you run the blade of a knife ove it?  (Read 14463 times)

paul.fr

  • Guest
You know, the sort of ribbon you attach to presents. Why does it curl up when you run the blade of a knife or scissors over it


 

Offline ukmicky

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 3011
    • View Profile
    • http://www.space-talk.com/
Hi Paul

You are probably stretching one side making it longer than the other
 

lyner

  • Guest
Yep. I'd go along with that.
I was well impressed when I first saw a girl in a shop wrapping presents that way. Mind you, she could have been creosoting a fence and I'd still have been impressed.
 [:I]
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
LOL.. One of my favorite things to do is wrap presents and curl ribbons... You can straighten the ribbon back out by putting the ribbon on the opposite side of the curve in the ribbon to reverse the process... If you want a curl you must first place the blade of the scissors behind the curve of the ribbon not on the top side of the arch in it.. Then apply pressure which causes friction all the way down the length of ribbon..  I wonder if heat from the friction adds to making the curl at all?
 

Offline rosalind dna

  • Neilep Level Member
  • ******
  • Posts: 2019
    • View Profile
I wonder if the ribbon curls as it's cut by your scissors that it
might not be shiny side of a ribbon but that the matt side which
receives the most pressure from the person cutting their ribbon(s).

Although I am mostly useless with curling ribbon on a parcel unless I twist around my fingers.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
So molecule layers nearer the scissors will expand from each others more than molecules being on the further side?
And it's have nothing to do with the heat generated then?

Otherwise I thought that as it is a 'plastic' material, ribbon...
But then it should have curled towards the scissor, not away from it:)
And it do curls away from the scissor, doesn't it?
Awh, it's so long ago I did that, curls I mean.
Just call me baldie:)

--

Checking up on it do seems to bend towards the scissor?
(Well it's almost xmas after all:)
And then it must be the molecule layers furthest away from the scissors that get 'expanded' from each other?
And then heat too might have something to do with it, contracting the plastic layers nearest the scissor?
Or?
« Last Edit: 30/11/2008 18:16:41 by yor_on »
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
I thought that the friction of the scissors created heat against the ribbon and it curled,.... as you do have to put good pressure over the edge as you pull it down the ribbon! Is that to much of a reach for a guess.. doesn't friction usually produce heat?
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Hah Karen...
Yess yes yes:)
Now we are two ::))

But according to the sources I've found on the Internet:(
They all talk about molecular layers stretching?

But when you 'draw' that ribbon against your scissors edge you certainly creates some heat.
It should be possible to test that, like creating a 'slow' press while drawing that ribbon over the edge of the scissor as compared to a 'quick hard draw'.
looking at the curling I mean.
Do this make sense at all?
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
I wonder if the molecular layers are stretched due to the heat from the friction..? LOL!
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Maybe heat causes the plastic to stretch thus also leads to the curling??? EH??
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Yep Karen, that's my thought too.
But you know how it is with new unproven theories, no matter how ingenious they might be:(
But history will redeem us:)
 

Offline elmejor

  • Jr. Member
  • **
  • Posts: 18
    • View Profile
i had read about it long back by some harvard professor who had explained it in detail.he had said "ribbon curls as its outer layer stretches and, therefore, expands, more than the inner layer that is pressed against the rod or scissors. Even when you're doing it with a pair of scissors, it's not absolutely flat-you're not pulling it flat"
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Hah, Harward, was it.
Well, that just goes to show you how much 'they' know about ribbons.

I can tell you that I found an absolute expert in my birthday cake last year.
She had ribbons all over, and she my dear man, said nothing, what so ever, about any outer layers?

And she sure knew about stretching too.
So choosing between her and some old moldy prefeser claiming that they're from Hayward...
I will follow the 'practical' experiment.


And according to her, there was a great interest for this kind of experiments.
Shows us that science will conquer.

Yep:)
« Last Edit: 04/12/2008 19:20:50 by yor_on »
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums