Thermal Hair is made from polypropylene fiber that changes color in reaction to changes in temperature.
Thermal Hair has a higher resistance to heat than kanekalon, but can still be sealed with a steamer and will melt under high, dry heat like a straightener/flat iron. It will not shrink when sealed, but will hold its shape once set.
If the ambient temperature of the room you're in is close to the point where the color changes, sometimes it will appear to get "stuck." For example, your hair might be purple in the bag, turn teal from the warmth of your hands when you remove it, then stay teal after you've set it down. You can get it to go back to purple by exposing it to a much colder temperature, like an ice pack.
Thermal Hair cannot "burn out" - the fiber will never stop being able to change colors.
Length: 19" (48 cm) folded, 38" (96 cm) unfolded.
Weight: 0.63 oz (18 g). Thermal hair comes in small packs that contain enough for a few braids, or for highlights/accents.
Color: Baby Pale Blue.
The color change for this one is subtle; it changes from pale blue to a lighter blue that's almost white.
This color needs to get quite hot before it will change; you'll most likely only see the lighter blue if you're out in the hot sun for an extended period of time. We were able to change the color from the darker blue to the lighter one in the second photo by using a hair dryer (from about a foot away and on the "low" setting to prevent melting).