There's an organisation in the Netherlands called Stichting Haarwensen. They make wigs for people who need them, mostly kids who lose their hair because of a medical condition (like cancer or alopecia). All this is possible because of people who cut their hair off when it's long enough and donate their braid to this organisation. I can't imagine a better way to switch hairstyles!
My hair is very thick and healthy, I've never bleached or dyed it or used any products other than shampoo and some curl defining cream. Ofcourse you can donate if you have used products, the only way you can't donate is if you have grey hair. My hair is just really perfect for making wigs apparently, they were very happy with my donation. My hair is so thick, that only two braids of my hair will be needed to make one wig, where usually about 4 or 5 wigs would be required.
The hairdresser started cutting, and kept cutting, and her hand started hurting. My braid was so thick! It's amazing, and I produced this without any effort. It just grows magically out of my head!
When my hair was finished and the braid was packed up, there was still a lot of hair on the ground. My new hairdo is way easier to manage. It dries a lot faster now and I don't get stuck under the strap of my bag. Or between the car door. Or in my coat zipper. Or with rats hanging off it. Actually, that last one still happens!