In July 1905, Madam C. J. Walker moved to Denver and began building her own system for scalp and hair: a Wonderful Hair Grower with shampoo, pomade, brushing and iron combs. By 1908 she had a parlor in Pittsburgh and Lelia College, and by 1910 an Indianapolis factory and laboratory. She built it as a routine, not a single jar, which is a useful lesson for anyone with hair that resists everything you give it.

Low porosity hair is the kind that resists water. A board-certified dermatologist, Shani Francis, told Allure that it is resistant to absorbing and losing water because of its tighter structure. In practice, low porosity hair products tend to sit on the surface and feel greasy, and the fix is lighter formulas, warmer conditions and a bit of patience. I think it is more about less product than more, which is a hard message in a category that sells the opposite.

The trick is to start light. Experts quoted by Allure and L'Oréal Paris point to water-based products, humectants first and lipids second, applied to wet hair. Bounce Curl's Thermal Guard Weightless Leave-In Conditioner Spray and Living Proof's Leave-In Conditioner & Detangler Spray are the airiest options here. Moroccanoil's Detangling All in One Leave-In works across hair types. Bumble and bumble's Curl Reactivator is a hydrating mist, and Ouidad's VitalCurl Gel-Cream, Redken's Hydrating Curl Cream, Moroccanoil's Curl Defining Cream and OUAI's Anti-Frizz Curl Styling Cream cover the curl-defining side.

One rule for low porosity hair: clarify regularly. Products pile up because they cannot get in, and L'Oréal Paris recommends clarifying as a routine step. If your hair feels coated one day after a wash, or your leave-in seems to do nothing, that's the sign.

Hard water makes it worse. Act+Acre's Clarifying Hard Water Shampoo is built for exactly that, and Living Proof's Clarifying Detox Shampoo and K18's Peptide Prep Clarifying Detox Shampoo are the modern, salon-shelf ones. Dae's Desert Detox Clarifying Shampoo is a good one to keep in the shower for a monthly reset.

Bumble and bumble's Sunday Clarifying Shampoo is named for the day I would use it. Drybar's On The Rocks Clarifying Charcoal Shampoo is for the heavy stylers, and adwoa beauty's Blue Tansy Clarifying Gel Shampoo is the gel-textured one. Mizani's Moisture Fusion Gentle Clarifying Shampoo is the one to try if harsh clarifiers leave you tight.

A note on the internet's favourite test: the float test, where a strand is dropped in a glass of water. L'Oréal itself warns that leftover conditioner and hard water can skew the result, so clarify first, then test. The spray test, where water beads on your hair for 30 seconds or more, is another quick check.

What I would skip: clarifying and heavy oiling in the same wash. Pick one job at a time.

Here is how I would choose: look for something that cleans without leaving hair tight, because tight hair is a sign the shampoo is too strong. The best shampoo for curly hair depends on what else is going on. If your scalp is oily but your curls are dry, you want a gentle wash with good slip.

Odele's Curl Defining No-Lather Shampoo is for anyone who prefers a wash that behaves more like a conditioner. Kérastase's Curl Manifesto Sulfate-Free Shampoo and Bounce Curl's Weightless Hydrating Shampoo are the two I would try first for low porosity: one has weightless in the name, and the other is sulfate-free. Living Proof's Curl Enhancing Shampoo is a solid everyday pick.

Olaplex's N°4CURL Bond Shaper is for hair that likes a bit more cushion, and Curlsmith's Curl Reset Detox Shampoo is the monthly clarifying one. SheaMoisture's Coconut & Hibiscus Curl & Shine is made for thick curls, and Not Your Mother's Curl Talk Bond Building is a friendly, easy choice for anyone starting out.

L'Oréal Paris suggests lukewarm rather than very hot water, and I'd take that seriously. Hot water feels good and often leaves curls rougher.

A pairing I like: a light curl shampoo weekly, and a clarifying one once a month. It keeps the slate clean without stripping.

What I would skip: a rich, butter-heavy shampoo on low porosity curls. It will sit there.

Start with heat. The experts in the Allure piece suggest gentle heat and steaming to help conditioner get in, and L'Oréal Paris suggests a steamer for 10 to 15 minutes before a mask, or over it, weekly or every other week. Skip it if your hair goes over-soft.

The Steam Bar's Deep Conditioning Heat Cap is the plainest way to do it at home, and their Scalp & Hair Hydrating Conditioner is the natural partner. Kérastase's Curl Manifesto Nourishing Mask, Curl Queen's Intense Therapy Masque and Olaplex's N°5CURL Bond Shaper are the deep conditioners I would choose for a weekend session.

Virtue's Curl Conditioner and Redken's All Soft Mega Curls are the everyday-friendly ones. Amika's Dream Routine Overnight Hydrating Hair Mask is for people who want to sleep on it, though I would test on a weekend first to see how your hair reacts.

A pairing I like: apply the conditioner to soaking wet hair, put on the cap, read a chapter and rinse with lukewarm water. Ten to fifteen minutes with warmth beats an hour without.

What I would skip: leaving a heavy mask on all night when your hair already resists absorbing anything. Warmth and time on wet hair does more than volume.

I think low porosity hair rewards a lighter hand than most people expect. Wash and clarify well, apply on wet hair, use warmth, and pick water-based products over rich ones. That is not a glamorous message, but it is the one that gets results.

So I would buy one weightless leave-in, one clarifying shampoo and one heat cap, and stop there. Use them for a month before you add anything else, because low porosity hair is easy to overload and slow to tell you so. Madam C. J. Walker built a whole system in Denver. Yours can start with a spray bottle. If you want to keep browsing, I also put together Hair Porosity Explained and Conditioner Moisturizing Enough for Dry Hair.