Why does hair crackle when combed on dry day?

Hair crackles on dry days due to a phenomenon called triboelectric charging. When you comb your hair on a dry day, the comb and your hair rub against each other, creating friction. This friction transfers electrons from the comb to your hair, giving your hair a negative charge while the comb acquires a positive charge.

Opposite charges attract, so your hair strands will be attracted to the comb. However, your hair strands are also negatively charged and repel each other. The combination of these attractive and repulsive forces causes your hair to stand on end and make a crackling sound.

The severity of the hair crackling effect depends on several factors, including the humidity level, the type of comb you are using, and the condition of your hair. On days with very low humidity, there is less water vapor in the air to help dissipate the electric charge, making the crackling effect more pronounced. Plastic combs tend to create more static electricity than metal or wooden combs due to their higher electrical resistivity. Dry and damaged hair is also more prone to static electricity since it has a rougher surface, which increases friction and the buildup of electric charge.

To reduce hair crackling, you can apply a small amount of hair conditioner or anti-static spray to your hair, which helps to reduce the friction between your hair and the comb and neutralizes the electric charge. Humidifying the air using a humidifier also helps in reducing static electricity. Another trick is to use a dryer sheet instead of a comb. The fabric of the dryer sheet creates less friction with your hair and helps mitigate the crackling sound.