CAN YOU REALLY DYE YOUR HAIR WITH TEA?: THE SCIENCE BEHIND THIS KITCHEN HAIR DYE
When I first heard about dyeing your hair with tea I had an immediate flashback to my junior high days. Back then, my young and somewhat experimental friends used to dye their hair using another pantry supply, Kool Aid, in hopes of getting the vibrant hues they’d seek out later in a bottle of Manic Panic. It never looked particularly becoming, because it didn’t dye evenly and the hair usually looked pretty dried out.
So when a friend mentioned tea hair dye, it gave me pause. On the one hand, home hair dyeing is a zone I don’t like to venture into, because it so often turns out poorly. On the other hand, tea extracts are phenomenal — they’re antioxidant-packed and help protect against UV damage — and are found in all sort of skin and hair products.
This 2009 article in Nylon Magazine describes famed master stylist and salon owner Philip Pelusi’s tips for at home tea dyeing. Of course, the article doesn’t mention exactly how much color you can expect, but I’d guess it wouldn’t be nearly as saturated as a dedicated hair dye. Though the article mentions that doing it frequently will result in darker and darker staining.
How exactly tea imparts color and whether it will stick is complicated, to say the least.
Where Does the Color in Tea Come from?
The color in tea comes from tannin, but not the ones you might think. The term “tannin” often gets used as a catchall terms for plant polyphenols, and because tannic acid can be an irritant that is dangerous when swallow or inhaled, it often makes people hesitant about the term “tannin.” But the tannin is tea is chemically different from other tannin, and tea does not contain tannic acid (Journal of Pharmaceutical Science and Research). In tea it is a reference to the complex of oxidized polyphenols found in tea, including epigallocatechin-3-gallate (EGCG), which contains catechin.
The color in tea comes from the tannins, or the complex of polyphenols.
How does it Color Hair? Option 1: Fixer
In the case of henna, tannic acid serves as a fixer.
Here is where things get a little tricky. In order to dye your hair for more than one wash, at least one of two things must happen. Either the polyphenols in the tea enter the hair shaft, undergo a process of oxidation, and color your hair or you must use a mordant or “fixer.” Otherwise, the dye sits on top of the cuticle layer and will be washed out the next time you shower.
Traditionally in dyeing textiles, catechin has been used with tannic acid, though it can also be used alone (Agricultural Ledger, Journal of the Society of the Chemical Industry). In this case, tannic acid serves as the fixer, also known as the mordants, which increases uptake and “stick-ability” of the dye. Mordants can also include heavy metals such as tin or copper (Fibers and Polymers). Because henna contains both catechins and tannic acid, it has both the dye component and the fixer to make hair dye last (Protein Textile Dyes).
Remember, the tannins in tea aren’t the same as those in henna and don’t contain this tannic acid. That might be why several natural fabric dyeing how-to’s recommend using a mordant for tea dyeing, as the color won’t stick or be as saturated without it. But this doesn’t necessarily mean that tea won’t color your hair at all (after all, you may have noticed that it colors your mug after a time).
How does it Color? Option 2: Oxidation
One report explained that while catechin and tannic acid created the deepest hues, similar color could be achieved by dyeing something several times with catechin. If this is a case, part of the coloring might be the result of oxidation. (Though as the article suggests, this likely won’t color your hair as much as it would if you used a fixer).
The brown color comes when phenols are oxidized to create o-quinones. An example you might have seen is when a freshly cut apple begins to brown quickly after exposure to air. Oxidation doesn’t necessarily happen in oxygen alone, however. Traditional permanent dyes work by means of oxidation and in that case the hydrogen peroxide serves as the oxidizer (Chemical Reviews).
Because there’s advice to use different teas for different colors, I’ll differentiate between the lighter teas and darker teas.
Green and Yellow Teas
Different teas provide different levels of colors because of how oxidation of tea works. First, let’s look at green tea.
One study found that it was possible for green tea to oxidize when the brew sat for an hour at a pH of 7.5 or when set under severe conditions of 90°C (194°F) for 15 minutes (Journal of Agricultural and Food Chemistry). So what happens when these polyphenols oxidizes?
A 2008 study found that catechins in green tea oxidized by polyphenol oxidase/O2 or peroxidase/H2O2 creates o-quinones and semiquinones (Journal of Agricultural and Food Chemistry). Quinones are the natural pigments found in plants that can be used for dyes (Chemgaroo). One of the quinones, lawsone, is the one found in henna.
When companies prepare green and yellow teas, they carefully avoid the oxidation process.
Black and Oolong Tea
In black and oolong teas, the oxidation process occurs when companies prepare them.
Black tea undergoes the same conversion of catechins to quinones, but it happens before you even brew your cup, or buy the tea bags, for that matter. Again, to use the mug as an illustration: Your green tea doesn’t seem to permanent dye your mug, but your black tea will.
In the case of black tea and oolong teas, oxidation of the leaf (and catechins) is part of the preparation process before you even buy it (Heiss). That means these come along with tea when you buy it, making this kind of tea more equipped for dyeing right away.
Interestingly, researchers found that milk helped stop this process, which explains why tea sans milk in a mug will leaves stains, while tea with milk does not.
Penetration and Longevity of Tea Hair Dye
How long tea dye works in your hair is dependent on whether it would be categorized as a semi-permanent or temporary dye. The different between the two is whether the molecules that create the color are small enough to penetrate the cuticle layer or whether they remain sitting on top of the cuticle layer.
I wasn’t able to find a molecular size that best penetrates hair, but the rule of thumb for skin is the 500 Dalton Rule, which states that anything under 500 dalton can penetrate the skin. Most oxidative dyes are around 300 dalton (Hair in Toxicology). Even if we safely assumed that molecules penetrating hair must be smaller than 500 dalton, at 458 dalton for EGCG and 290.27 for catechin, it seems possible that the catechin could penetrate through the cuticle and dye the hair semi-permanently.
Since black tea comes with quinones right away and many lighter teas are persevered from the enzymatic oxidation that produces these, darker teas will likely have more of an effect on hair than lighter teas. And much like the report of catechin dyes for textiles above, it may take several dyes (allowing the tea to soak in your hair) to get a good color.
It’s possible that tea could penetrate through the cuticular layer and change hair color semi-permanently.
While you won’t go from having black hair to platinum blonde hair, there’s a chance you can change you hair color slightly with tea. You’ll probably have better luck with darker teas because they’ve already undergone some of the necessary oxidation process to impart dark color on your hair. Tea dyeing also won’t last as long if you just let your hair soak it up as it would if you used a mordant or fixer. Overall, if you’re looking for a dye that won’t have ill effects on your hair, doesn’t have a profound effect, and won’t necessarily last a long time, tea can be a great way to color hair. In fact, researchers are already figuring out ways to optimize the oxidation process of catechin in order to use it in hair dyes in the future (JCDSA).
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