The length of your haircuts are not guided by your scissors alone. The manner in which you hold the hair between your fingers is just as important. Tension is what controls the amount of pressure you place on the hair when you lift the head to cut it and this decides how straight the hair hangs before you cut it. An even tension allows the hair to hang naturally and the shape will hang smooth and even. A tension that is not consistent from one head section to the next will cause your hair shape to hang unevenly even though your cutting line may have looked even when you cut it. Start by simply observing how the hair reacts to your tension.
Comb a small section of hair straight down and then place your fingers at the end of the hair and lift it straight out from the head. Now notice how the hair will stretch when you apply a bit more pressure and then will hang more naturally when you ease up on it. Now cut a tiny bit of hair off the end of one section using a light amount of tension and then cut another section using a bit more tension. When you allow the hair to hang back down you will notice that the section you used more tension on will appear to be shorter because you stretched the hair when you cut it.
One of the most common mistakes you can make with tension is to inadvertently change your tension as you cut the hair. You may cut the front sections with a firmer tension because you are concentrating on what you are doing and then loosen up a bit as you cut the back sections because you have become more comfortable. This will cause your hair length to become uneven and will be a bit more difficult to fix later. To prevent this from happening, stop and readjust your fingers as you cut around the head.
Comb the section of hair and then place your fingers back down at the same distance from the head that you did the last time. This will help you keep your tension consistent and prevent you from allowing your tension to fluctuate as you cut your hair shape. You can practice your tension control in short intervals. Take a fifteen minute period of time and just work on one small section of hair. If you have a mannequin head, just work on the back panel. Comb the hair straight down and then lift it up to the same height. Now simply place your fingers in it without cutting.
Then let it down and just repeat this action several times, paying close attention to how hard you are pulling on the hair. Once you feel like you have a consistent tension, just trim a couple of millimeters of hair off and observe how the length hangs back down naturally. You are not concerned with taking the length of the hair down at this point. You are only concerned with control. If you practice in short intervals like this on a regular basis, your hands will eventually learn what the right amount of tension is and the hair will begin to hang more evenly from each cut.
The outline of your shape will become more distinct and you will begin to see a more professional looking haircut develop. So even though your tension seems like a minor detail compared to actually cutting the hair with your scissors, it has a major effect on the outcome of your haircut. Once you have mastered your tension, you can develop a consistency with your haircuts that will make the difference for you between hacking at someone’s hair and being able to craft a good haircut.