Differences Between Acid and Alkaline Perm, Which one should you choose for your hair?

first days

Do you want to know what kind of perm suits your hair? An acid perm or alkaline?


You’re not the only one.

Now that perms are once again at the crest of the new wave of popular hairstyles, my clients are bursting with questions.

What curl suits me best? How long will my curls last? Should I use a blow dryer to dry my curlers?


  • To keep things short, alkaline perms are ideal for people with thick hair. Later on I’ll explain why.
  • Now, what happens if you have fine or very damaged hair? In this case the best perm for you is an acid perm.


Even though this isn’t one of the most frequently asked questions-because ultimately it’s the hair stylist who decides what kind of perm to do-I must admit I was surprised when one of my clients, Raquel, came in with this question.

One day she asked me, “Karina, what’s the difference between an acid and an alkaline perm?


Maybe she has a toddler, or was thinking of studying to be a hairdresser, or maybe she was just one of those information junkies roaming the internet.

Knowing her how I know her, I’m inclined to believe that she’s just a cautious person who feels the need to have all the information before deciding on putting her hair through any process such as getting a perm.


I understood her concern. Because after all, with any kind of perm, strong chemical products are used in order to modify the natural pattern and form of the hair.


Because of this, if you’re thinking about getting a perm, and you want to know every last detail about what happens to your hair, keep reading and I’ll tell you:

  • What kind of hair are alkaline perms suited for
  • In what cases is it best to apply an acid perm


Afterwards you’ll almost be an expert…almost.

But don’t be fooled. It’s always better to have a professional perm your hair. Because it’s not just about using the correct products.

It’s also very important to choose the appropriate curler and place it correctly to achieve the shape of curl you want to show off.


Now let’s take a look at the differences between alkaline and acid perms.


Tabla de Contenidos


What kinds of hair are alkaline perms suited for

Experience tells me that it’s always better to explain with examples. After all even Jesus used parables to be understood by the masses.

I’m not trying to put myself on his level, not by any means, though I will follow his example.


Going back to my client Raquel. She has very, very thick hair. The kind of hair that appears double the volume due to its thickness.

Generally, thick hair is the most envied, because it’s the most resistant to any kind of processing.

But when it comes to getting a perm, this can be a disadvantage.

Can you imagine why?


Because thick hair is heavier. This doesn’t mean that when you hop on the scale all the extra pounds are you hair’s fault.

No, that would be the extra sweets and carbohydrates.

 So, in undertaking perming Raquel’s hair, she would run the risk of her curls losing shape over time due to their weight. 


To be sure that wouldn’t happen, I decided to give her an alkaline perm.

For this kind of perm ammonium thioglycolate is used, which, besides being a powerful chemical, also has quite a nasty smell.

Though truth be told, not nearly as nasty as in the 80’s.


Furthermore, alkaline perms contain a low level of acidity, between 9.0 and 9.6 pH, and the process is much quicker than for acid perms.

It only takes about 20 minutes to take effect. They’re “cold” perms and don’t require the application of additional heat.

That’s why I decided to give Raquel’s hair an alkaline perm.

And I wasn’t wrong.


The result was incredible, even though for the first few moments of the application of the perm solution, Raquel complained about the unpleasant smell.

As my grandmother would say, “If you want to make an omelet, you have to break some eggs…”


Regardless, when it was all said and done, Raquel jumped with glee. Her hair, thick and motionless, was flaunting some curls in the shape of spirals that gave it an almost wild look.

Which is exactly what she was looking for.


In Mercedes’ case things were different.

Want to know why? Keep reading.


In what cases is it best to apply an acid perm

Mercedes came in with the thought of getting a perm, and no one was going to convince her otherwise.

After carefully examining her hair, I decided I could go through with the process.

But that I would give her an acid perm.

Can you guess why?


If you were paying any attention to what I explained at the beginning, I bet you can.

 Mercedes’ hair was very fine, but furthermore, it was considerably neglected. Not to the point of drying out, but still neglected. 

On the other hand, if her hair had been completely ruined, I never would have been able to give her a perm.


Acid perms contain glyceryl monothioglycolate, a “milder” formula.

Another difference is that, being milder, they require heat to activate the perm solution.


 Now, acid perms have a big disadvantage to alkaline perms, and it’s that the curls can last less time because the formula is milder. 

While an alkaline perm lasts around 6 months, an acid perm, given the care it deserves, can last between 3 to 4 months.


This could be discouraging if you have fine hair and you want to get a perm, but consider the following.

What would you prefer? A perm that lasts a long time but ruins your hair or a perm that lasts less time, but gives you healthy curls?


When I finished Mercedes’ acid perm, we were both ecstatic.

I was because I knew I had made the right decision. Her hair wouldn’t have been able to handle an alkaline perm.

And she was because she now had so much more volume and movement in her hair that had truly looked sad when she first came in.


Now you know the differences between an alkaline and an acid perm.

So which one do you think is right for your kind of hair?


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