The Science of Household Tips: Does vinegar actually set dye in jeans?

[terriko]

When I bought my latest pair of jeans, the nice lady who helped me find them advised me to wash them with a cup of vinegar the first time, to better set the dye. I didn't think much of it, until I wore the jeans before washing them and ended up with mildly blue thighs. So clearly pre-washing would have been a good idea, but.. does vinegar actually set dye?

Googling this mostly turned up a bunch of people parroting the same tip. Which would be reassuring if I didn't know that the internet is a sucker for feasible-sounding tips regardless of they make sense or work. (Witness: Pinterest vs Pinstrosity)

My research turned up the following claims, from the ever-reputable source of "people on the internet"

1. Vinegar totally helps set dye in jeans
2. Vinegar totally helps set dye... but not in cotton, so you're wasting your time with jeans.
3. For jeans, you should really use salt, not vinegar
4. Actually, you shouldn't wash jeans at all
5. It doesn't matter, but for the love of all that is blue, wash your jeans in cold water
6. You need to wash your jeans inside-out
7. Mine totally leaked dye so I gave them away and bought new ones!

But 0% of these came with sources that gave me any indication if these were really legit or just old wives tales. I don't need scientific journal papers, but you'd think there'd at least be a science fair project or tests from some sort of cross between consumer reports and good housekeeping.

So where do you go for figuring out if there's actually any proof behind household tips like this?

Comments

[(Anonymous)]

Blue Jeans use "Indigo Dye" - C16H10N2O2, also called "indigotin" for colour. It's a readily available synthetic compound based on a pigment found in a Japanese plant.
http://en.wikipedia.org/wiki/Indigo_dye

The blue dye is only soluble in water of it's exposed to an acid (which has the side-effect of turning it green - indigo/carmine). So theoretically it'd be useful to add vinegar to remove excess dye. (and keep your legs from staining) I don't buy the setting thing, though.

A similar pigment compound, Prussian Blue, reacts and sets in the presence of other acids, but that's hardly ever used in fabric dyes anymore since it tends to break down into cyanide. So maybe it's a really old wives' tale from before indigo dye was popular?

-Jay

[frith]

I couldn't find it on Snopes.

Home Comforts

[(Anonymous)]

The book Home Comforts by Cheryl Mendelson is my go to for matters of home economics. It says the colorfastness is really a matter from the factory and not much can be done after the fact.

Re: Home Comforts

[terriko]

I've also had Hints from Heloise recommended as a source of tried and true tips.

But what I really want to see is a collection of experiments to see what actually happens. Mythbusters for home ec, only with better science, I guess?

[ivy]

I would probably buy a couple pairs of jeans and run the experiment myself, but that's nothing like statistical significance. I might also ask my fabric arts friends who do their own dyeing and might know. I sympathize with your frustration over bad information, though.

[maco]

If the dye used was an acid-based dye, it could make sense. Certainly vinegar is used to set plenty of dyes overall (think Easter eggs), but that doesn't necessarily translate to all dyes on all materials. If you want to get excess overdye out of them so they stop turning things blue, get Synthrapol. It's used both to prepare fabric for dyeing and remove overdye.

Blue Dye

[(Anonymous)]

I just found blue jeans that finally really fit, but my hands, couch, body, etc turn blue when I wear them. I have washed them several times now. I still have it rubbing off.
I will try the vinegar next time to see if it works.

[kimiko]

Found your blog post while looking for an article to your very question. I found it, and thought you might want to read it. It is just the summary article, not super in depth, but based on actual scientific research which is cited in the article, and that full research can also be found online it seems.
NF91-44 Ineffectiveness of Home Remedy Dye Setting Treatments
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2440&context=extensionhist

thank you

[(Anonymous)]

I'm puzzled after that definitive disproval there was no acknowledgement. Anyway it answers my friend's question perfectly, thanks. :)

Re: thank you

[terriko]

Yeah, a belated thank you from me as well. The response came so late after the original post that I wasn't really paying attention to response, but I do appreciate the data!

Use 1 cup of salt in washer to set and keep your colors bright

[(Anonymous)]

I found this on a diy site and wanted to pass on the info. I think I can offer a bit of help with the fading. Your very first step should be to pre-wash the shirt according to the manufacturers directions. You'll find the washing instructions on the little tag on the inside of the shirt. Manufacturers add chemicals to the dying process so if you wash your shirt first it will be chemical free and less likely to fade since you're not adding the ink over a layer of treated fabric. After completing the shirt you will want to do a second washing, but this time you will need to add one cup of ordinary table salt to the washer along with your detergent.I have used this salt trick for years and it really helps keep fading to a minimum. Being a bit of a skeptic, I did my own experiment before ever using salt in all my new washable clothing I bought several new yellow bath towels and kept one of them in the closet not used. After a dozen or more washings I compared the laundered towels to the brand new unused towel. It worked!!! The laundered towels were just as bright as the one stashed in my closet. I keep the big box of salt on the shelf above my machine so I don't forget to use it. I hope this helps you. Great instructable!

Re: Use 1 cup of salt in washer to set and keep your colors bright

[terriko]

While I'm glad this worked for you, this doesn't really help for what I wanted, which was some sort of scientific-ish study of the efficacy of vinegar. I found lots of posts with anecdotal suggestions, but not so much in the way of science!