General Question

Magnus's avatar

How come fat makes paper transparent?

Asked by Magnus (2871points) August 3rd, 2008

I have this paperbag of nachos, and parts of it are pretty transparent. Now this didn’t surprise me much, but the fact that it stays transparent even when its perfectly dry surprised me. Please explain this.

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5 Answers

Indy318's avatar

It had to do with refraction of light and how the fat molecules fill in the air between the paper fibers.
http://www.paperonweb.com/A1047.htm

—I tried linking it but it goes back to the original question (probably because I’m on my iPod).

marinelife's avatar

Magnus Great Question! I have always wondered this. From paperonweb:

“Normally when we look at paper the surrounding medium is air, with an index of refraction only slightly greater than 1.0. The paper fibers have a much higher index of refraction—probably much greater than 1.5.

The fat also has a high index of refraction so that it nearly matches the index of refraction of the paper fibers and it reduces the scattering significantly. The fat adhering to the cellulose fibers lowers the index of refraction of the cellulose and also fills in air voids, so that visible light passes through the bag with significantly less scattering. Now we only see the light that is reflected from the paper and much of the light that was formerly scattered back to our eyes is now transmitted through the paper.

The fat connects the fibers in the paper with a liquid which can transmit by refraction (rather than scatter) light that falls upon it. As a result, the paper (if thin enough) seems almost transparent. ”

Indy318's avatar

never mind it seems to be working fine now.

Btw, nice link Marina. :)

kapuerajam's avatar

BWA-ha-ha-ha I can finaly make a fake “El latigo tm ” signal and lure him into my trap!!!!

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