Why did bleach turn these white pants pink?
August 2, 2015 3:39 PM Subscribe
My girlfriend recently dunked white pants in bleach water and before our very eyes some previously light yellow stains turned bright pink. What caused that?
Here's the long version of the story: she ran a load of whites with some chlorine bleach in the water. When it was done one pair of her pants had pink stains in weird places - some behind the knee, a little bit on the waistband. We couldn't figure out why it happened. She tried soaking them in a light bleach solution, did no good. She went out and bought some OxiClean and soaked them in that. The formerly pink stains turned yellow. After a few rinses and re-soaks (over a couple of days) the stains more or less disappeared.
Today we were looking at the pants in sunlight and incandescent to see if the stains were light enough to ignore, or if she needed to put them through another OxiClean bath. She said, "Maybe they show up more when wet" and dunked her pants in a bucket with water and just a little bit of bleach (which she had put together in anticipation of having to bleach them further anyway). Immediately all the yellow stains reverted to pink and our minds melted.
The only thing I've been able to find on the internet is some guy claiming yellow stains from "a new brand of sunscreen (P20 - an alcohol based apply-once-a-day)" turned pink when exposed to bleach. She maintains she's never worn sunscreen while wearing these pants, and hasn't even worn them the day after wearing sunscreen, didn't set them on top of sunscreen'd clothing in the hamper, etc.
We're at a loss, at this point. The pants are back in an Oxi bath for another day or two and then shall never see bleach again, apparently. But now she's worried (and I'm morbidly curious, I guess) about what might have triggered this so she can avoid getting it anywhere near her whites ever again.
Here's the long version of the story: she ran a load of whites with some chlorine bleach in the water. When it was done one pair of her pants had pink stains in weird places - some behind the knee, a little bit on the waistband. We couldn't figure out why it happened. She tried soaking them in a light bleach solution, did no good. She went out and bought some OxiClean and soaked them in that. The formerly pink stains turned yellow. After a few rinses and re-soaks (over a couple of days) the stains more or less disappeared.
Today we were looking at the pants in sunlight and incandescent to see if the stains were light enough to ignore, or if she needed to put them through another OxiClean bath. She said, "Maybe they show up more when wet" and dunked her pants in a bucket with water and just a little bit of bleach (which she had put together in anticipation of having to bleach them further anyway). Immediately all the yellow stains reverted to pink and our minds melted.
The only thing I've been able to find on the internet is some guy claiming yellow stains from "a new brand of sunscreen (P20 - an alcohol based apply-once-a-day)" turned pink when exposed to bleach. She maintains she's never worn sunscreen while wearing these pants, and hasn't even worn them the day after wearing sunscreen, didn't set them on top of sunscreen'd clothing in the hamper, etc.
We're at a loss, at this point. The pants are back in an Oxi bath for another day or two and then shall never see bleach again, apparently. But now she's worried (and I'm morbidly curious, I guess) about what might have triggered this so she can avoid getting it anywhere near her whites ever again.
Okay, I don't have an explanation, just another curious anecdote that maybe some smarter person will be able to do something with. I usually clean my toilet with Sal Suds (if you're not familiar, it's just plain liquid detergent) and a toilet brush. Last week the toilet seemed a little smelly to me, so I put some bleach in the water. Uneventful so far. Then I put the toilet brush in, and immediately all the water and the brush turned pink. THEN it all went back to normal. ???
posted by HotToddy at 4:33 PM on August 2, 2015
posted by HotToddy at 4:33 PM on August 2, 2015
I've had this happen with white towels! IME a lot of white fabrics have been dyed white and when you expose them to bleach or hydrogen peroxide they expose their original colors.
posted by Hermione Granger at 5:03 PM on August 2, 2015 [3 favorites]
posted by Hermione Granger at 5:03 PM on August 2, 2015 [3 favorites]
This happens to me when I need to put more salt in the water softener (to combat our super iron-y well water).
posted by cecic at 6:29 PM on August 2, 2015 [1 favorite]
posted by cecic at 6:29 PM on August 2, 2015 [1 favorite]
Sunscreen makes some weird colored stains when mixed with bleach.
posted by KMoney at 7:56 PM on August 2, 2015
posted by KMoney at 7:56 PM on August 2, 2015
> Then I put the toilet brush in, and immediately all the water and the brush turned pink.
This might support andrewcooke's iron theory, as the wire in your brush (assuming a standard brush which is a loop of twisted wire to which the bristles are attached) is probably unloading surface rust into the water.
posted by Sunburnt at 8:02 PM on August 2, 2015 [2 favorites]
This might support andrewcooke's iron theory, as the wire in your brush (assuming a standard brush which is a loop of twisted wire to which the bristles are attached) is probably unloading surface rust into the water.
posted by Sunburnt at 8:02 PM on August 2, 2015 [2 favorites]
This sounds like the behavior of a pH indicator to me. Both bleach and OxiClean are pretty alkaline, but that doesn't rule out the possibility that your diluted bleach and OxiClean solutions were substantially different in pH. A list of naturally occurring indicators. Turmeric, which is a key ingredient in curry powder, is a red-yellow indicator, but would probably change color at a substantially lower (closer to neutral/acid) pH than I would have expected either of your cleaning solutions to be.
posted by gingerest at 10:40 PM on August 2, 2015
posted by gingerest at 10:40 PM on August 2, 2015
Best answer: Manganese in your stain would explain the disappearing/reappearing bright pink. Like many other transition metals, its color can change when its oxidation state changes, and is bright pink when in its highest oxidation state.
Bleach (sodium hypochlorite) will oxidize manganese to permanganate (+7 oxidation), which is a characteristic purply-pink color. So if you use Clorox (NaClO) bleach again, if you've manganese stuck to the cloth fibers, you'll end up with the pinky sodium permanganate (pink!)
While Oxiclean (peroxide) is typically an oxidizing agent, in its reaction with permanganate it gets oxidized, and the permanganate gets reduced to Mn+2, which can be an pale orangey-brown color (see also pic here). Here's a video in action of hydrogen peroxide with permanganate: pink to colorless! It probably wasn't as dramz as that on your pants, but you probably saw some bubbling action (the O2 formed in the reaction).
(If you have iron in your water, that would be the Lewis acid needed for the reaction above to take place--see Fenton's reagent.)
As far as how it got on the pants in the first place: Manganese is in dirt, if that's what the original stain was. It's also in hard water. If you've got hard water, you're better off sticking to peroxide bleaches like Oxiclean instead of hypochlorite bleach anyways. Martha Stewart agrees!--she knows that chlorine bleach, the stronger oxidizer, will get more iron to the ferric oxidation state (+3), leading to worse orangey-yellow spots on your clothes.
posted by neda at 1:58 AM on August 3, 2015 [9 favorites]
Bleach (sodium hypochlorite) will oxidize manganese to permanganate (+7 oxidation), which is a characteristic purply-pink color. So if you use Clorox (NaClO) bleach again, if you've manganese stuck to the cloth fibers, you'll end up with the pinky sodium permanganate (pink!)
While Oxiclean (peroxide) is typically an oxidizing agent, in its reaction with permanganate it gets oxidized, and the permanganate gets reduced to Mn+2, which can be an pale orangey-brown color (see also pic here). Here's a video in action of hydrogen peroxide with permanganate: pink to colorless! It probably wasn't as dramz as that on your pants, but you probably saw some bubbling action (the O2 formed in the reaction).
(If you have iron in your water, that would be the Lewis acid needed for the reaction above to take place--see Fenton's reagent.)
As far as how it got on the pants in the first place: Manganese is in dirt, if that's what the original stain was. It's also in hard water. If you've got hard water, you're better off sticking to peroxide bleaches like Oxiclean instead of hypochlorite bleach anyways. Martha Stewart agrees!--she knows that chlorine bleach, the stronger oxidizer, will get more iron to the ferric oxidation state (+3), leading to worse orangey-yellow spots on your clothes.
posted by neda at 1:58 AM on August 3, 2015 [9 favorites]
(Disclaimer: I swear I'm not trying to hijack your ask! It just seems that additional data might be helpful.) In support of Neda's suggestion, I know for sure that my water is very high in manganese. Regarding the toilet brush/iron suggestion, I checked the brush and it's only plastic bristles in a plastic wand, no wire.
posted by HotToddy at 3:41 PM on August 3, 2015
posted by HotToddy at 3:41 PM on August 3, 2015
(I think Neda's hypothesis is more plausible than mine.)
posted by gingerest at 7:37 PM on August 3, 2015
posted by gingerest at 7:37 PM on August 3, 2015
This thread is closed to new comments.
posted by andrewcooke at 4:15 PM on August 2, 2015 [1 favorite]