The Science of Curly Hair Typing

Is there any science to hair typing? Can it help you find the right products for your hair? We break down the history and science of hair typing.

March 8, 2025

The Science of Hair Typing

Hair typing is a mainstay of the curly hair community. The typing system created by Oprah's hair stylist Andre Walker in 1999 is the most popular system with types like 1a, 2b, 3c, and 4c. But is hair typing just marketing made up to sell more products? Or is it an actually useful system that can help you find the right techniques and products for your hair?

The history of hair typing and role of race

The idea of there being different hair types didn't start in 1999 with Walker's system. Scientific research on hair in the past hundred years typically classified hair based on race with only three types: Caucasian, Asian, and African. Unfortunately these classifications failed to capture much of the diversity within populations.

That's not to say that your ancestry doesn't matter. Large scale surveys of hair suggest that there are patterns of hair types based on recent ancestry, but there is also a lot of overlap and diversity within those groups ^[1]. The genetics of curly hair are extremely complicated, which makes the ability to classify hair important for discovering the genes behind it ^[2] ^[3].

Biological anthropologist Dr. Tina Lasisi is interested in understanding how hair evolved and has theorized that the tightly coiled hair type may be an adaptation to hot climates. This type of hair is only present in people with recent African ancestry as it likely evolved after other populations left the continent. She outlines her research in her graduate thesis which is a really good read if you are interested in the subject ^[4] and she has an episode of her show Why Am I Like This? Why Do We Have Different Hair Types? available online.

One part that's really interesting is where she talks about a rare condition of coiled hair in people with European ancestry called "Uncombable hair syndrome" where she points out the name and the idea of it being a "syndrome" are rooted in Eurocentric ideas about hair

the language used to describe [uncombable hair syndrome] hair aligns with pejorative racialized descriptions of what is commonly stereotyped as “African” hair.. the combing of hair hardly seems like a criterion for determining health. If styling potential were indeed a medical concern, there is an apparent lack of an equivalent “unbraidable hair syndrome” for individuals whose hair is too limp to hold a braid. But holding hair’s ability to be “combed flat” in higher esteem than its ability to be braided can be explained by the regard for criteria of “whiteness” and associated beauty standards

As someone who is not Black, I have to appreciate that there is a lot of context I may not have about hair, racism, and culture. I'm grateful for the new generation of Black women who are researching hair.

Racism regarding hair has real consequences for people, including but not limited to discrimination at work, which has been well studied and documented ^[5].The idea that hair texture is a spectrum is true, but I don't want it to take away from the unique Black history and cultural context here.

Scientific approaches to hair typing

There are many criticisms of Andre Walker's system ^[6], but in a way he was far ahead of science. Even recent scientific papers still used the old racial hair typing system.

Walker's system is the most popular hair typing system because it is targeted at consumers with the the idea they could compare their own hair to illustrations on a chart.

Walker's system has 4 types: straight (1), wavy (2), curly (3), and kinky (4). Within those types there were subcategories for different patterns from a-c. Originally only types 1 and 2 had a-c, with 3 and 4 only having a and b, but these days many charts have a-c for all types. It's a simple system but has received criticism for oversimplifying the diversity in types 3-4 and reinforcing hierarchies that focus on 3 being the desired type.

But it wasn't until around 2007 that scientific researchers really tried to make their own attempt at hair typing. There are many factors that make hair typing a challenge scientifically. Hair texture can vary between different hairs on one person's head, it can be affected by hair care, humidity, and other factors. What measurements do you use? Scientists have attempted many measurements ranging from curve diameter to number of twists. How do you measure the hair? Since as hair gets curlier it gets more and more complicated, you can't just tape it to a piece of paper and measure it. Scientists have resorted to everything from suspending it in resin to 3d scanning in order to take accurate measurements.

This first major attempt is usually called the STAM system, named after Segmentation Tree Analysis, the statistical technique that the researchers used ^[7]. Researchers took a large (1442 people) geographically diverse sample and utilized curve diameter, number of waves, and number of twists as measurements. Once they had the measurements they used Segmentation Tree Analysis to reveal clusters and each cluster became a type in their system. They ended up with 8 types and became the standard for researchers moving away from the racial system.

The L'Oréal System built on the STAM system with slightly different measurements and with product development in mind ^[8]. It used curve diameter and number of waves, but instead of number of twists it used a "curl meter" measurement involving placing a curl in a circle and seeing how much fit inside of it.

The very recent Gaines-Page system was developed by materials scientist Dr. Michelle K. Gaines and her research assistant Imani Page at Spelman College, a HBCU (Historically Black College/University) ^[9].

The Gaines team utilized techniques from materials science and engineering such as bright field and scanning electron microscopy. They didn't want to utilize the same hair diameter measurements used by L'Oreal and others because hair diameter can vary from root to tip and between different hairs on the same person. Instead they decided on a system using contour length, number of contours in a fixed distance (3 cm), pitch, and contour to length ratio.

Measurements used in the Gaines-Page hair typing system

Interestingly, their system lines up very well with Walker's. But that's likely because they used nine local samples from the Atlanta area. It will be interesting to see what happens when the technique is applied to a more geographically diverse sample.

Gaines-page hair typing compared to Walker hair typing

Dr. Tina Lasisi reevaluated the L'Oreal system using samples from an ethnically mixed (African/European) population and found that there was way more diversity within the tightly curled variation of the spectrum. This suggests that a larger sample size might reveal there are actually more different types of tightly curled hair ^[10].

our terminology for describing skin color variation and hair curvature variation overemphasize the relatively small range of variation shown in European populations while minimizing the considerable range of variation shown in African and African-descendant populations.

Her sample size was small (140), but suggests the possibility that a truly diverse hair typing system might have over 75% the types just devoted to diversity in very curly and tightly coiled hair.

Lasisi statistical analysis of hair types

Lasisi's data also seems to show that people are not very good at typing their own hair, unless they have straight hair.

A promising new typing system is the Irizarry Hair Texture Scale from quantitative sociologist, race scholar, and survey methodologist Dr. Yasmiyn Irizarry ^[5]. It is notable for being both academic and also accessible for the average person, as well as considering socio-cultural dimensions when typing.

It also puts coils at the starting end of the scale and straight at the end, challenging the Eurocentric notions that may have put straight hair at the starting point of other scales.

The Irizarry scale also incorporates shrinkage, which is a concept that other scales miss and can be really important for understanding and caring for hair. Shrinkage is usually defined as the degree of length change between wet and dry hair, but it also is how much the hair can be stretched out from its resting state.

How to tell your hair type in the new systems

Many of the systems discussed here require special equipment for classification.

However, Gaines says that anyone can get the idea of what hair Gaines-Page type may be using the system her team developed ^[11] ^[12]:

Pluck out a strand of your hair and place it unstretched on a ruler. Then, by simply counting the number of contours that repeat within a certain length, you can say “my hair fits into this type and this shape” and give it a number

The length in the paper is 3cm.

The Irizarry typing involves a survey you can find in the paper. First a question on your primary texture: coily(1), curly, wavy, or straight(6). One thing that's unique is it gives you the option to select that you're between these textures. Like it's possible to be between wavy and straight (5).

Then based on your answer it gives you two choices that have information about shape, shrinkage, and how it hair behaves when styling.

What hair typing means for your hair care

So this all seems very interesting for science but I bet you're wondering what it means for your own haircare. Unfortunately as a lot of this research is new and more research is needed, it can be hard to tease out real recommendations especially as it relates to types that are similar or hair that is between/multiple types. But here is what we know now:

Dry detangling is less damaging for straighter hair and more damaging for curlier hair

In straighter hair, dry styling is less damaging than wet styling, but in curlier hair it's the opposite. The wetting decreases curvature, which decreases resistance to forces like combing ^[13].

Combing forces on different types of hair

This also means that products that help reduce that resistance even more when wet are crucial such as rich slippery conditioners.

The verdict: So if your hair experiences a lot of shrinkage (hair is much longer wet than dry) avoid dry detangling and instead opt for wet detangling, ideally with a product that enhances slip such as a conditioner or a detangling product.

If your hair is in between straight and curly you'll need to pay attention to how water affects your curl. If your hair is less curly when wet, you should opt for wet detangling.

Curlier hair has more trouble distributing sebum and may need products that substitute for it

Sebum is our natural scalp oils, which can provide natural lubrication between strands, prevent moisture loss, and natural shine. Straighter hair some sebum naturally travels down the shaft to the rest of the hair, but that's physically harder for curlier hair ^[14]. This phenomenon might account for why some studies show that curlier hair has less shine ^[3].

Additionally, straighter hair can brush the sebum down the shaft to distribute it without as much resistance. For curlier hair, dry brushing is just going to cause more damage than it's worth because of the resistance from the curls.

The distribution of oils being different may also affect products. Oils applied to the scalp in tightly curled/coiled hair may be more likely to buildup and cause fungal growth ^[15].

The verdict: If your hair is curlier, your might want to look into oils on the ends (squalane and jojoba are thought to be particularly similar to sebum) and products that provide the same qualities without feeding bacteria/fungi closer to the scalp such as cationic conditioners, silicones and fatty alcohols ^[16].

If your hair is straighter you can dry brush to help distribute sebum but be mindful of how your hair resists it. For curlier hair, avoid dry brushing. Dry brushing is just going to cause more damage than it's worth because of the resistance from the curls.

Since I have the infamous "Irish curls" (mixed loose curls,waves, and straight sections) I sometimes use a boar bristle brush on stringy straight/lightly wavy sections but I avoid using it on curly sections.

Curlier hair is more likely to need special products for low or mixed porosity

Gaines and her team found that curlier hair tends to be lower porosity ^[11] ^[16]. They believe this is because the cuticle layers are smaller and more tightly packed, potentially making it harder for moisture to stay locked in.

Cuticle layers in wavy (left) vs. curly (right) hair(Gaines)

Wavy and straight hair retains moisture longer, likely due to larger, more widely spaced cuticle layers that allow for smoother moisture retention.

Other researchers have found that weathering from grooming actions can cause curlier hair to have more severe cracks than straighter because the cuticle cells get compressed into one another ^[13].

This suggests that longer curlier hair might be even more prone to be mixed porosity, with low porosity towards the scalp and more damaged ends, especially if it is not protected.

The verdict: Deep conditioning and regular moisturizing are especially crucial for curly and coily hair to prevent excessive dryness.

Curlier hair needs more protection from knots and breakage

For example Gaines' team subjected different types of hair to stress and found that curlier hair can be stretched out longer than straight hair before breaking, but that stretching can cause the hair to weaken and deform from stress. Protection against these forces is key for curlier hair ^[3].

Coiled hair also forms a type of knot that doesn't seem to occur in straighter hair. So things that protect against these knots are crucial, from protective hairstyles, to products that decrease friction to silk pillowcases and bonnets ^[3] ^[2] ^[13].

The verdict: The curlier your hair is, the more important it is to protect it using products that decrease friction. Use silk pillowcases, bonnets, and products that decrease friction.

Unfortunately one of the best things to decrease friction is silicones and many people avoid those. You might want to rethink silicones or look for substitutes like Lexfeel Wow-A (Triheptanoin and C13-16 Isoalkane).

For straighter hair, protective things can be useful but aren't as critical. I like my silk pillowcase but if I forget it while traveling it's more of an annoyance than a serious threat to my hair's health.

There are also certain protective styles that aren't possible or more difficult for straighter hair such as locs. When people with straighter hair try those styles it's more for style than protection.

It is interesting to think about what Gaines' research might mean for styling type 3 and 4 hair. If you have any thoughts on that, please let me know!

Straighter hair gets can loose volume from oil and other heavy ingredients

We covered how curlier hair might benefit from oils and conditioning ingredients that add shine. Tighter curls can resist the weight from these ingredients without loosing volume.The looser your curl pattern the more you have to worry about these ingredients weighing your hair down, clumping it, and making it limp and greasy ^[13]

Shrinkage may be a good measurement of this, because it often correlates with the strength of the curl pattern. Hair that experiences a lot of shrinkage is going to be less weighed down by products.

The verdict: If you have hair that's closer to straighter/wavier you'll want to be careful with oils and other heavy ingredients and aware that they can weigh your hair down. In addition, washing out these things well (and also sebum)plays a bigger role in volume.

Wavy hair may be closer to straight hair for care needs

This one is the most controversial/theoretical and would be a practical application of Lasisi's research showing that the the spectrum of hair curliness would have more types for curlier hair than the conventional systems.

Theoretical hair type chart based on Lasisi's research

It's almost a rite of passage for people with hair closer to wavy to try to our products formulated for coily/curlier hair and practices like cowashing and finding that they don't work very well for us.

There is a lot of overlap though. Products with a lot of conditioners are good for both lubrication and protectin of coily/very curly hair AND preventing static in wavy/straight hair. The main divide seems to be heavier oils/butters, which weigh down wavy/straight hair.

Also someone closer to wavy than curly, I've also been experimenting with serums meant to be applied on dry hair for dry brushing and smoothing (including silicone serums), which are usually formulated for straighter hair. The main difference from a straight hair routine now would be I use some products with hold, such as a light-weight foam, to prevent frizz and hold my wave/curl pattern better.

It's also possible that wavy hair would receive different (perhaps more?) benefits from volumizing products containing protein.

The verdict: If you have wavy hair, you may be able to use products formulated for straighter hair with good results.

Conclusion

It's exciting to know that scientists are delving into different curl types and in the future we may get even better recommendations in the future.

Yes, marketing is part of it, companies do want to develop more targeted product lines, but that doesn't mean it's not real and it doesn't mean it's not useful.