Have you ever heard the sound of hair literally frying? Take it from me, it’s not pleasant. While I’m sure we’ve all had our fair share of embarrassing beauty mishaps to laugh off, mine didn’t just entail poor blending skills or mismatched foundation shades (though I’m guilty of those, too—I swear I’m a beauty writer, team). Rather, my personal mishap involves long-term damage to my hair that I’m still trying to mend years later.

Though I technically have virgin hair that’s never been color-treated or chemically altered, I used to be a major abuser of heat styling tools, flat-ironing through my sopping wet waves for years on end and failing to use heat protectants while doing so (cringe-worthy, I’m aware). I still have vivid memories of standing in front of my bathroom mirror, ironing my post-shower hair (sizzling sound and all), and cheerfully singing along to a Backstreet Boys tune, completely oblivious of what my hair would inevitably become in the future.

What was once luscious, thick, perfectly-tousled locks has transformed into dry, lackluster, straw-like strands thanks to my poor hair choices as a teen. All that to say, my method of revitalizing my hair thus far has always been trial and error-influenced by over-promised marketing claims, usually to be met with disappointment and, ultimately, shadows of regret.

Recently, though, I had the opportunity to consult with hairstylist Leigh Hardges of Chicago’s Maxine Salon, who let me in on a hair porosity test that costs exactly $0 and can tell you a lot about your hair and how to treat it.

What is hair porosity?

“Hair porosity refers to the state or condition of the hair’s outer layer called the cuticle,” says Hardges. “It determines the hair’s ability to accept and hold onto a foreign substance.” Think of the cuticle like a snake or fish scale. “When the ‘scales’ all lay flat and tightly together, you have a smooth hair strand (aka low porosity hair)—products can’t easily pass through the cuticle layer and end up just sitting on top,” explains Hardges. “Low porosity hair is typically wavy to straight, feels heavy and dense, and takes forever to dry.” That said, though this hair type is prone to build-up and repels moisture, it’s more likely to appear shiny because of the smooth cuticle layer.

Then there’s high porosity hair, which, unlike its low porosity counterpart, features open “scales” of the cuticle. “High porosity hair is typically wavy to coily or kinky. The curl pattern in the hair shaft makes it very difficult for the ‘scales’ to remain closed, thus making it prone to frizz,” says Hedges. “Products absorb easily into the hair strands, but they also escape, so it may feel like products never ‘work.'”

If your hair lives between the two worlds and has partially open “scales,” your hair is medium porosity, which means it’s balanced and requires the least amount of maintenance. Because the “scales” are slightly raised, strands are able to accept moisture more readily (versus low porosity hair), but because they’re not fully open (like high porosity hair), the moisture is retained.

Why should you test your hair’s porosity?

Simply put, porosity is the missing link that most hair enthusiasts aren’t aware of, but Hardges maintains that the opening and closing of the cuticle is the gateway to effective hair color, chemical alteration (by way of relaxers, straighteners, or perms), and styling. “Knowing your hair porosity can help you understand your hair’s boundaries and how far it can be pushed,” she says. It’s knowing the why of your hair, which will help you make educated hair purchases versus impulse buys that you’re just hoping will work.

How should you test your hair’s porosity?

Here are the exact steps that I followed to conduct the porosity test:

1. 1.
   Shampoo the hair squeaky clean and don’t condition (It’s important to avoid conditioning the hair for this test, as hair that’s coated with oil will naturally float to the top, skewing the results.)
2. 2.
   Allow hair to air dry.
3. 3.
   Fill a medium to large bowl half full with water.
4. 4.
   Pluck a strand from your head.
5. 5.
   Place the hair strand into the water.

Determining Your Hair Porosity

My hair immediately floated to the top, which means I have low porosity hair. Hardges says that this hair type is more resistant to styling, so I should be mindful of the amount of heat styling I do (oops). She also recommends avoiding heavy creams, as they can tend to sit on the hair and make it stringy (double oops). Instead, she says to stick with lighter products, such as Paul Labrecque Repair Style Hydrating Hair Lotion, $28, that can rinse out easily.

If the hair remains suspended in the middle, you have medium porosity hair. “Product selection for medium porosity hair can take a little more trial and error,” notes Hardges. “This texture definitely wants to avoid heavy oils and silicones, as they can weigh the hair down and make it difficult to style.” You’re also prone to tangles and knots, so she says to take care while detangling with a product such as Kinky-Curly Knot Today Leave-In Detangler, $12.

Hair that sinks to the bottom means it’s highly porous. “This is the most fragile of all hair types, so it’s important to be gentle and deliberate with your hair care,” advises Hardges. “Minimize how often you shampoo and stick to butters, creams, deep conditioners, masks, and treatments.” We like Briogeo Don’t Despair, Repair! Deep Conditioning Hair Mask ($36). She also calls out acid-based rinses (like lemon or apple cider vinegar) to assist with closing the cuticle for a smoother hair strand.

Hardges recommends giving the water test a whirl whenever you notice a significant change in the feel of your hair, as well as before and after a color or chemical service to see how affected your hair is by the service.