A great way to up-cycle the thread used in the fabric dyeing process, or any other laying around, is to make Kumihimo out of it. A type of braid that has been used in Japan for centuries and is still seen in things like tea ceremony bags (Shifuku), or the braids to tie the Obi around the Kimono (Obijime).
We tied the indigo dyed thread around the bobbins, then placed them on the Marudai with weights hanging from the middle to stabilize the braiding process. I started off with a 4 string braid, a simple but time consuming process. It took me around two hours to make a 140cm long Kumihimo.
Then I gave it a second try with purple silk thread, a result of dying it with madder and later on with indigo, and blue linen thread dyed with indigo. This time I used 8 threads.
Mine are round and simple, but a Kumihimo can also be flat or braided with intricate patterns with over 40 threads. If you ever go to the Tokyo National Museum, check out the Samurai armors or the sword handles and look closer to find beautiful Kumihimo samples.