Jump to main content

Watt’s Up? Why the Effect Isn’t the Most Important Thing About Your Blow-Dryer

Is one of the first things you ask while purchasing a new blow-dryer how many watts it has? You’re not alone.

But did you know that for hairdressers, it doesn’t actually matter? Read on for more information on hair drying, watt, and what’s really important.

The Optimal Drying Effect

Many believe that in order to dry the hair quickly, blow-dryers need a certain amount of effect, where a higher number of watts is considered better. This is not the case. According to scientific studies, there is an optimal level for drying hair. Here is the explanation:

The drying speed is influenced by two factors:

  • The air humidity
  • The speed of the air

These two factors have a threshold that there is no need to exceed. For example, the humidity of the air that leaves the blow-dryer is under 4 percent if the temperature is 80°C, even in a humid bathroom.

Increasing the temperature above 80°C has no effect on the time the hair takes to dry.

Did you know that it’s important that the hair is a little damp when you start blow drying? It’s the only way you can make the hair keep its shape until the next wash.

Don’t Let the Hair "Faint"

It’s not unlikely that you have over-dried a section of the hair and felt that the hair has “fainted”. No matter how hard you try to revive it, the hair remains lifeless and without elasticity.

This can be explained:

When the hair already is dry, its temperature rises when it’s continually exposed to the hot air. Its natural bounce gets “burnt out” if it’s blow dried over and over again.

Relative Humidity

What happens, and I’m sorry for having to get a bit technical here, is that the air in the salon gets warmer and pushed in the direction the nozzle is pointing. The air in the room has a given temperature, for example 22°C, and a given humidity (which is the amount of water in grams per cubic metre of air). The absolute humidity isn’t very important in this context.

The important thing is, is the relative humidity, which is the air’s ability to absorb water molecules. The relative humidity is dependent on the temperature of the air. In other words, by warming the air through the blow-dryer, you also increase the air’s ability to absorb moisture.

The lower the humidity in the air, the more “drying power” it has. Understand?

Yes, it’s like saying that the beer gets cold quicker in the freezer than in the fridge, because the freezer has more “freezing power”. And the other way around as well: You have likely seen the dew that appears on a cold glass of beer on a warm summer day? What happens is that the temperature of the air close to the glass decreases, and that way its ability to hold humidity. And bam! Your glass has condensation.

Hot, But Not Too Hot

To get the water in the wet hair to transition into a gas form, a lot of energy is needed. What happens in the hair when is transformed from a liquid to a gas is that the water collects evaporation energy from the hair (in addition to the air).

Are you cold after you get out of the sea? It’s the same thing. The temperature in the hair is kept lower than the temperature of the drying air. And as long as the hair is wet, the temperature in the hair will be at what we call the wet sphere temperature. But when the free water has evaporated, the temperature in the hair will increase until it reaches the same temperature as the drying air.

Charged Ions

The hair doesn’t benefit from being heated up to high temperatures like this. The heating element inside of the blow-dryer is very warm, and dust and pollution in the air can split and create charged ions. These will also impact proteins, oil, and other desirable components of the hair. It creates discoloration and smell.

Water and hair are also charged with positive ions, and that’s why most good blow-dryers have ionizers that add negative ions. It loosens “charged” water from the hair easier and cuts down the drying time.

Do you want to know more about drying techniques? Check out this post!

Fast, but not too fast

The same goes for the speed of the airflow. What’s important is removing water molecules that lie closest to the airspace around the strands of hair. You can do this by creating turbulence in the air around each strand. A sufficient airflow from the blow-dryer makes the hair blow, and this creates enough turbulence to remove the water.

Increasing the power further doesn’t help. Not even the strengths of a hurricane would matter for the drying speed.

Conclusion: Increasing the airflow and the heat do not reduce the time it takes for hair to dry. It’s about getting the right combination of the two that gives the optimal effect for drying. The perfect combination of airflow and heat leaves the hair naturally bouncy and will leave it looking shiny for days.

Are you on the lookout for a blow-dryer that dries the hair optimally, completely without overheating the hair? Learn more about the Dual Air T1™