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. Boiling water generally is not hot enough to seal it. 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." You can get it to go back to the other color by exposing it to heat or cold (depending on what color it is and what you want to change to).
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: 0.78-0.88 oz (22-25 g). Thermal hair comes in small packs that contain enough for a few braids, or for highlights/accents.
Color: Pastel Green/Yellow.
This color needs to get quite hot before it will change; you'll most likely only see the yellow if you're out in the hot sun for an extended period of time. We were able to change the color from green to yellow in the second photo by using a hair dryer (from about a foot away and on the "low" setting to prevent melting).