Wax Rubbed on Paper: Why Paper Becomes Translucent

  • Thread starter khil_phys
  • Start date
  • Tags
    Paper Wax
In summary: I think the difficulty in explaining it comes down to a couple of things. One is that its an everyday experience and we take it for granted, and secondly, its a biochemical process that we don't really understand very well.
  • #1
khil_phys
93
0
Why does paper become translucent when wax, butter or oil is rubbed on it?
 
Physics news on Phys.org
  • #2
I have always assumed that it is because the wax (or oil or whatever) more closely approximates the refractive index of the paper than the air that would otherwise separate the fibers in the dense mat that we call "paper".

The amount of reflection and the amount of refraction taking place at an interface is going to depend in large part on the difference in the refractive indexes of the materials on each side of the interface.
 
  • #3
Interesting question and I'm surprised this forum isn't full of variiations on it.
I, also would think it's to do with refractive index but it could do with Total Internal Reflection. When light arrives at dry paper, there is no internal reflection (air having a low refractive index) so tends to get absorbed by the fibres. When there is water or grease, the light could be totally reflected at the interfaces and find itself penetrating much greater depth of the material by a series of reflections. I imagine there will be some fibrous substances that would show this effect less and some would show it more.
I did have another idea and that is to do with the surface, when it's wet. It's much flatter and would not scatter the light so much, possibly allowing more light to cross the interface (on the way in and out) - more specular.
 
  • #4
^^^^^^^

Exactly what I was thinking about the scattering and a lens effect when the oil gets in between all the fibres that hold little oil "window panes". So you have essentially made a smoother product that allows light to penetrate.

On a biochemical level lots of paper products are extraordinarily good (paper towels) at holding oil which one might not expect based on the fact that they are mostly carbohydrates which are polar. But processed cellulose (and unprocessed cellulose as well) take on some extremely hydrophobic characteristics as well so it can sop up oil and water. Kind like a solid soap in one sense. Its an amphipathic product.
 
  • #5
Why isn't there a theory on this? I mean, I was "taught" this 7 years ago in primary school, and took it as a fact. This is most certainly an everyday experience. What might be the hurdles in explaining this phenomenon?
 
  • #6
khil_phys said:
Why isn't there a theory on this? I mean, I was "taught" this 7 years ago in primary school, and took it as a fact. This is most certainly an everyday experience. What might be the hurdles in explaining this phenomenon?

You'll have to do some research of your own and make a name for yourself as an expert!
 
  • #7
I think the idea is that the fibre/air refractive index ratio is very high so light is highly refracted, and scattered, when it hits the dry paper. The wax replaces the air in the paper, and the fibre/wax refractive index ratio is far closer to unity so the incident light tends not to undergo so much refraction, and can be transmitted through the material without being significantly scattered.
 
  • #8
khil_phys said:
Why isn't there a theory on this? I mean, I was "taught" this 7 years ago in primary school, and took it as a fact. This is most certainly an everyday experience. What might be the hurdles in explaining this phenomenon?

Took what as fact?
 
  • #9
pgardn said:
Took what as fact?
This very phenomenon.
 
  • #10
Well I imagine quite a few people have noticed the same phenomena.

But your question was why does oil cause paper to appear translucent. People are discussing the why, not the apparent fact that the paper does appear translucent.

Its a very good question. Its one of those types of questions that lots of people notice but never contemplate the why part of the observation.
 

Related to Wax Rubbed on Paper: Why Paper Becomes Translucent

1. How does wax make paper translucent?

Wax is an opaque substance that has a low refractive index, meaning it does not bend or scatter light. When wax is rubbed onto paper, it fills in the small pores and crevices on the paper's surface, creating a smooth and even layer. This layer of wax allows light to pass through without being scattered, making the paper appear translucent.

2. What types of wax can be used to make paper translucent?

Any type of wax can be used to make paper translucent, however, some are more effective than others. Beeswax and paraffin wax are commonly used due to their low melting points and ability to spread easily on paper. Candle wax, soy wax, and even crayons can also be used, but may require more effort to achieve a consistent and smooth layer.

3. Does the amount of wax applied affect the level of translucency?

Yes, the amount of wax applied to paper directly affects the level of translucency. A thin layer of wax will make the paper slightly translucent, while a thicker layer will make it more opaque. It is important to find the right balance to achieve the desired level of translucency without making the paper too fragile or difficult to handle.

4. Why does wax make paper more durable?

Wax has a protective and waterproofing effect on paper. When wax is applied to paper, it creates a barrier that prevents water or other liquids from being absorbed, making the paper less likely to tear or wrinkle. This is why waxed paper is commonly used for food packaging and other applications that require durability.

5. Can waxed paper be recycled?

It depends on the type of wax used. Beeswax and soy wax are biodegradable and can be recycled with paper. However, paraffin wax and other synthetic waxes are not biodegradable and cannot be recycled. It is best to check with your local recycling center to see if they accept waxed paper for recycling.

Similar threads

B Increase in radiation from radium pocket watch hands
    • High Energy, Nuclear, Particle Physics
Replies
6
Views
1K
3D subsurface laser engraving for translucent minerals?
    • Optics
Replies
5
Views
2K
Why and How Ethanol + Water + Raw Material contain Essential Oil
    • Materials and Chemical Engineering
Replies
7
Views
2K
Study on ruled vs unruled paper?
    • STEM Academic Advising
2
Replies
52
Views
4K
We Bought a House (A materials question)
    • General Discussion
Replies
8
Views
1K
Why paper contracts when burnt?
    • Other Physics Topics
Replies
5
Views
1K
B Why is Maldacena's paper published in two journals?
    • Beyond the Standard Models
Replies
12
Views
2K
Other Becoming anxious since my paper was submitted to journals
    • STEM Academic Advising
Replies
8
Views
3K
Why does stainless steel float when coated with wax?
    • Other Physics Topics
Replies
4
Views
5K
B Do Materials' Elastic Properties Influence Motion and Force Equilibrium?
    • Other Physics Topics
Replies
18
Views
2K

Hot Threads

Recent Insights

Back
Top