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The Effects Of Water On Heat-Styling Damage

The Effects Of Water On Heat-Styling Damage

Hi Stylists,

Have you ever wondered whether heat protectant sprays were worth the effort? Here’s the science behind how to protect your hair from heat styling damage!


What damage occurs when you use heat to style hair?

Straighteners and curling irons heat your hair to somewhere between 95 and 170 °C. When your hair heats up above 130 °C (266 °F), a few types of damage occur:

  • The pigments that give your hair its color change (e.g. bleached hair goes brassy)
  • The keratin proteins that give your hair its strength and elasticity break down
  • The outer surface (cuticle) of the hair cracks and frays
  • Moisture evaporates from the inside of the hair (and if your hair is wet, the steam will blast through your hair’s structure, destroying it as it leaves)


Styling hair with straightening irons or curling tongs to achieve smoother, straighter hairstyles, or curls and waves, has grown in popularity. This has created a large market for hair products associated with heat styling, these include heat-protection sprays, straightening balms, curl creams, and heat-protection shampoos and conditioners.

Heat-styling damage from blow drying and hot irons can be both physical and chemical in nature.

Cycles of wetting and blow-drying hair can result in the formation of multiple, “axial” cracks in the cuticles, therefore hair fibers undergo rapid dehydration, a rapid escape of water while drying which can increased hair breakage on combing.

Most heat-protection sprays on the market present to protect the hair, however, they all, at present, are formulated as water or water/ethanol-based products.

In this study, they investigate whether the water in a heat-protection spray can affect the level of damage caused by heat styling. Tryptophan damage from heat styling was measured using fluorescence spectroscopy, and structural damage was investigated using light microscopy and single-fiber tensile testing. Hair samples were heat treated with straightening irons, following treatment with either a water-based, “wet,” heat-protection spray or an ethanol-based, “dry,” spray.

Results showed that, as expected, tryptophan damage was reduced by repeated applications of both the “wet” and “dry” heat-protection sprays. However, no differences were seen between the “wet” versus the “dry” product. Light microscopy studies showed greater structural damage to hair treated with water and the “wet” spray. Tensile tests confirmed that there was greater damage to hair treated with the “wet” spray.

The results of this study suggest that the type of damage caused by heat treatments is different in wet versus dry hair. In dry hair, thermal treatments cause chemical damage and some structural damage. However, in wet hair, thermal treatments cause the same chemical damage, but considerably more structural damage, which causes significant changes in the physical properties of the hair. It is likely that the rapid evaporation of water from the hair is the main causal factor.

Their experiments suggest that the effectiveness of commercial heat-protection sprays can be improved by the removal of water and by the use of volatile ingredients, such as ethanol, as base solvents.

In this picture you can see light microscopic images of hair fibers, illustrating the increased structural damage observed in hair treated with straightening irons for 12 × 5 seconds (×60 magnification). A, C, and E are focused on the cuticle and surface. B, D, and F are focused on the cortex and medulla.

CONCLUSION This study has confirmed that it is best to use straightening irons on dry hair to reduce structural damage. Furthermore, it is best to use a “dry” heat-protection spray to help keep damage to a minimum. They do not recommend to use heat protectant sprays on dry hair and then style with a heated iron.


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