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Aside

Unit 29 – The Science of Towels

Difficulty: Medium

Time: 6 minutes

One of the questions here is slightly Section Three-esque, however, knowledge of chemistry should not be required to answer the question. The main challenge with this unit will be getting it all done in under 6 minutes, as the questions themselves are not too difficult. 

 

The passages below have been adapted from a series of articles from Why Can’t Elephants Jump, published by New Scientist and edited by Mick O’ Hare.

 

Passage 1
Some garments made of 100 per cent cotton will hang-dry on the washing line without creases, while other pure cotton items end up covered with stubborn creases that only a steam iron will shift. Why is this? Is it the quality of the cotton, or perhaps the species of cotton plant it comes from? And while we’re on the subject, some cotton towels never really absorb the moisture from your body, however many times they are washed, while others – initially resistant while new – age into the job perfectly well after visiting the washing machine. What’s going on?

 

1. In Passage 1, the distinction made between ‘100 per cent cotton’ and ‘pure cotton’ is:

  • A      Explicit
  • B      Inquisitive
  • C      For literary effect
  • D      Convoluted

 

Passage 2
One of the reasons for a difference in crease retention is that cotton varies in its fineness. Fine cotton tends to form fewer creases than coarse fibre cotton. Also, a tight weave will tend to crease more than a loose weave, and woven fabrics will crease more than knitted fabrics.
Washing is responsible for most creases found in the fabric. When cellulose, an essential component of all plants, including cotton, gets wet, the hydrogen bonds holding it in shape are broken. If the fabric is dried in a creased state, new bonds form that hold these creases in place, where they stay, sometimes even after vigorous ironing.
Many cotton fabrics today receive chemical crease-resistant treatments. The presence, type or quality of this treatment is the likely reason you are experiencing major differences in the crease retention of cotton garments. Regarding towels, one made with pile yarns consisting of fine fibres will dry you much better than a towel made with yarns consisting of coarse fibres. This is because fine fibres form a greater number of finer capillaries that wick the water away from the body more efficiently.
Years ago, all towels were made with loops of fibre, or terry, on both sides of the towel. Today, many are sold with looped terry on one side and a cut pile of single fibres on the other. The fibres on the side of the towel that has the cut-pile tend to separate, which reduces their water-attracting capillary action and by consequence their ability to dry your skin.

 

2. Based on evidence from Passage 2, the crease-resistant chemical treatments applied to cotton fabrics could work by:

  • A      Refining the fibres
  • B      Preventing hydrogen from bonding with water.
  • C      Un-looping the fibres
  • D      Preventing the fabric from getting wet

 

Passage 3
A very high percentage of what is labelled 100 per cent cotton has been chemically treated to enhance the properties of the garment or linen. Much of this treatment is focused on modifying the surface of the fibre.
In the 1950s cotton fabric was treated with epichlorohydrin, which very effectively prevented wrinkling by keeping the individual fibres straight and a little springy. Unfortunately the compound weakened the fabric, so it was replaced by new treatments, including resin coatings. Many of these coatings are still in use today.
If you have ever visited a fabric shop, you may recall a pungent odour. This comes from the formaldehyde that is used to treat cotton fabrics and is present in a type of phenolic formaldehyde resin. The latest fabric surface treatments include Teflon resins to provide wrinkle resistance and prevent staining.
Some towels and bed sheets are treated with heavier coatings of polymers to give a very soft feel which, while pleasing, has the unintended consequence of repelling water. I personally discard any towels with this permanent softener treatment because they remind me of trying to dry myself with a plastic bag.
Incidentally, it would be prudent to thoroughly wash any new garment before wearing it and allowing it into contact with the skin. Many of the cotton treatments described above can be hazardous for those working with them during manufacture – for example, some fabric softeners can trigger allergic reactions.

 

3. Based on evidence from Passages 2 & 3, which of the following towels would be the most prone to creasing?

  • A      A looped-fibre towel treated with phenolic formaldehyde
  • B      A fine fibre, knitted towel treated with Teflon
  • C      An untreated, woven fine-fibre towel
  • D      A coarse fibre towel coated heavily in polymers

 

4. Based on evidence from Passages 2 & 3, which of the following towels would be the best at absorbing moisture?

  • A      A heavily polymer-coated, looped-fibre towel
  • B      A coarse fibre towel treated with epichlorohydrin
  • C      A fine fibre towel lightly coated with polymers
  • D      A fine fibre, looped-terry towel
  • Answers:
    Q1: C
    “Some garments made of 100 per cent cotton will hang-dry on the washing line without creases, while other pure cotton items end up covered with stubborn creases that only a steam iron will shift.”
    The inclusion of the word ‘other’ suggests that the writer does not mean to make a physical distinction between 100 per cent cotton and pure cotton.

    Q2: B
    How it happens:
    “When cellulose, an essential component of all plants, including cotton, gets wet, the hydrogen bonds holding it in shape are broken.”
    The crease-resistant chemical treatments therefore work by preventing these bonds from breaking. The bonds are broken when the Hydrogen bonds with the water, so by preventing this from happening the bonds will not be broken.

    Q3: D
    When it comes to creasing, coarse fibre towels are more likely to crease than fine fibre towels. “Also, a tight weave will tend to crease more than a loose weave, and woven fabrics will crease more than knitted fabrics.”
    Polymer coatings do not effect the creasing, they just make the towel soft.
    This leaves us with D: a coarse fibre towel (1 point for creasing)
    and C: A towel which is woven ( + 1 creasing point) but also fine-fibre (-1 creasing point). We lack any additional information about towel D, so all things equal this is the most likely to crease.

    Q4: D
    “Some towels and bed sheets are treated with heavier coatings of polymers to give a very soft feel which, while pleasing, has the unintended consequence of repelling water.” This rules out A and C.
    Whether the fibre is fine or coarse effects the creasing, not the water absorption, and looped terry fibres > epichlorohydrin (which is an anti-creasing agent)

    Gamsat Sample Questions

    June 9, 2012

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