# Why does saran wrap erase the print from thermal paper?

**URL:** <https://boards.straightdope.com/t/why-does-saran-wrap-erase-the-print-from-thermal-paper/514377>\
**Category:** Factual Questions\
**Created:** [October 19, 2009, 7:12pm UTC](https://boards.straightdope.com/t/why-does-saran-wrap-erase-the-print-from-thermal-paper/514377 "2009-10-19T19:12:26Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\
**Post date:** [October 19, 2009, 7:12pm UTC](https://boards.straightdope.com/t/why-does-saran-wrap-erase-the-print-from-thermal-paper/514377/1 "2009-10-19T19:12:26Z")

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So here at work I have a lot stuff on thermal paper (invoices from vendors, certain customer receipts etc). Some of these, just due to the sheer amount of them, I bundle up by the month and wrap saran wrap\* around them a few times to hold them together so I can toss them in a bin for storage.  
The odd thing I’ve noticed is that after about a week any of the the thermal print that is in contact with the saran wrap disappears. Why? Anyone have any idea about that?  
\*It’s not saran wrap per se, it’s the type of wrap you’d see in a grocery store on cut produce or a thinner version of what you’d see wrapped around meat or fish.

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**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\
**Post date:** [October 19, 2009, 7:32pm UTC](https://boards.straightdope.com/t/why-does-saran-wrap-erase-the-print-from-thermal-paper/514377/2 "2009-10-19T19:32:03Z")

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> [@Joey\_P](#):
>
> So here at work I have a lot stuff on thermal paper (invoices from vendors, certain customer receipts etc). Some of these, just due to the sheer amount of them, I bundle up by the month and wrap saran wrap\* around them a few times to hold them together so I can toss them in a bin for storage.  
> The odd thing I’ve noticed is that after about a week any of the the thermal print that is in contact with the saran wrap disappears. Why? Anyone have any idea about that?  
> \*It’s not saran wrap per se, it’s the type of wrap you’d see in a grocery store on cut produce or a thinner version of what you’d see wrapped around meat or fish.

Plastic wraps are usually loaded with plasticizers. These may react with the thermal phase change dye.

> **[Leuco dye](https://en.wikipedia.org/wiki/Leuco_dye)**
>
> A leuco dye (from the Greek λευκό leuko: white ) is a dye which can switch between two chemical forms, one of which is colorless. Reversible transformations can be caused by heat, light or pH, resulting in examples of thermochromism, photochromism and halochromism, respectively. Irreversible transformations typically involve reduction or oxidation. The colorless form is sometimes referred to as the leuco form.
> Leuco dyes form the basis of thermal printer papers and certain pH indicators.
> The mo...