Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: Raftrommelmans on 13/11/2018 10:53:40

Title: Why would beetroot juice cause a slowly growing stain on a touchscreen?
Post by: Raftrommelmans on 13/11/2018 10:53:40

A month or so ago my colleague placed a beetroot juice stained thumb on his Samsung smartphone touchscreen leaving a stain. He was unable to clean it off entirely as it had seemingly seeped into the very screen itself. The stain has since then spread slowly but steadily and taking over more screen real estate every week.
I've added two photographs of the screen, one taken on oktober 26th, which was about 2 weeks after "the incident". And now one taken today, november 13th. There is nothing "on" the screen, the juice was also wiped off almost immediatly after contact and taking screenshots of itself shows a perfectly clear picture.

20181026s.jpg (326.34 kB . 797x1611 - viewed 4521 times)

20181113s.jpg (496.43 kB . 1224x1632 - viewed 4452 times)

What does beetroot juice contain that causes this slow but steady creeping screen-infestation?

Title: Re: Why would beetroot juice cause a slowly growing stain on a touchscreen?
Post by: chris on 13/11/2018 13:36:50

Wow! Beetroot has got a lot of complex molecules in the dye, including the dark red anthocyanins that give it its colour, and a host of other antioxidants organic molecules; but what's happening to the phone looks a bit too dramatic to be just down to the beetroot; and the dye should not be able to penetrate the screen in the first place. I wonder if something else is going on?

Title: Re: Why would beetroot juice cause a slowly growing stain on a touchscreen?
Post by: chiralSPO on 13/11/2018 13:47:48

It looks to me like the beet juice has gotten between the screen protector and the actual phone screen, and then is effectively seeping by capillary action. I am surprised that the rate is on the order of several mm per day--I would have expected it to be either much faster or much slower--but it is what it is.

I think the major takeaway is that the compounds responsible for the color are so intensely colored that even a very, very thin layer is showing up to be extremely dark. It also looks like there may even be some separation of the different compounds, akin to thin-layer chromatography (https://en.wikipedia.org/wiki/Thin-layer_chromatography)

Very cool, and very unfortunate at the same time. (though I suspect that if the screen protector is removed, a damp kimwipe should be able to remove the offending stain.)

Title: Re: Why would beetroot juice cause a slowly growing stain on a touchscreen?
Post by: Raftrommelmans on 13/11/2018 15:59:13

That does sound plausible, allthough I can add that there is no screen protector on the phone. It's underneath the actual glass of the phone. It could of course have seeped in on that side of the phone, but as it was explained to me, there was no prolonged period of submersion, just a dab with a moist and tinted thumb.

Title: Re: Why would beetroot juice cause a slowly growing stain on a touchscreen?
Post by: RD on 13/11/2018 19:51:01

Abandon the beetroot-hypothesis ...

(https://forums.androidcentral.com/attachments/samsung-galaxy-s3-canada-bell-telus-rogers/182769d1434868883t-phone-fell-purple-ooze-slowly-growing-across-screen-image.jpg)

https://forums.androidcentral.com  phone-fell-purple-ooze-slowly-growing-across-screen.html (https://forums.androidcentral.com/samsung-galaxy-s3-canada-bell-telus-rogers/332892-phone-fell-purple-ooze-slowly-growing-across-screen.html)

Title: Re: Why would beetroot juice cause a slowly growing stain on a touchscreen?
Post by: Bored chemist on 13/11/2018 20:43:08

Quote from: chris on 13/11/2018 13:36:50

Beetroot has got a lot of complex molecules in the dye, including the dark red anthocyanins that give it its colour,

Not that it matters much but beetroot is unusual in that the red colour isn't from anthocyanin.

https://en.wikipedia.org/wiki/Betanin

Title: Re: Why would beetroot juice cause a slowly growing stain on a touchscreen?
Post by: RD on 14/11/2018 03:08:25

.
https://forums.att.com/t5/Android/ (https://forums.att.com/t5/Android/Why-is-this-not-covered-under-warranty/td-p/4337187)

Another Samsung phone gone over to the dark-side.png (319.47 kB . 508x613 - viewed 3584 times)

Title: Re: Why would beetroot juice cause a slowly growing stain on a touchscreen?
Post by: chris on 15/11/2018 18:09:30

Quote from: Bored chemist on 13/11/2018 20:43:08

Quote from: chris on 13/11/2018 13:36:50

Beetroot has got a lot of complex molecules in the dye, including the dark red anthocyanins that give it its colour,

Not that it matters much but beetroot is unusual in that the red colour isn't from anthocyanin.

https://en.wikipedia.org/wiki/Betanin

Whoops! Thanks for putting me right!