In this picture you see quite a pile that I have collected from a variety of places. The small one on the upper left is one of the first headband's that I made for Blythe. I will be using it as an example of size for Blythe. But I made that one without anything to go from, and it was not too difficult to approximate the size. The bluegreen headband on the lower left was my first attempt for an example project, but it turned out to be too thin to demonstrate with. I learned that these very thin headbands (while they may look great on Blythe) are very difficult to shrink, so it is best to wait until you have some experience to tackle these types.
As far as tools go, you will need some picture wire or other medium weight wire to bind to size and handle for suspension in boiling water, dikes for cutting down to size after shrinking, a file for finishing the ends after diking, and a pot to boil the headbands. I do not use my good cooking pots for this just in case some nasty plastic type chemicals are released during the boiling process. Here are my tools:
So that's the preparation. Down to task: get the pot of water boiling. It needs to be deep enough that you can put the headband in for a few (2) minutes without touching the side or bottom of the pan.
Select your first headband. You may want to choose one that is not your favorite for your first trial.
Bend it so that the headband ends cross each other quite a bit and the band looks close to the right size for Blythe. I show that step here with an already shrunken headband for clarity, but you really will be able to estimate that size. I did for the gold example one.
Bind the headband together to retain that size. It's a little easier said than done, but mainly, you just need to wrap the wire around enough times to secure it.
So, your water should be boiling by now. Using the wire for a handle, you need to immerse the headband in boiling water for about 2 minutes. No cheating on the time. If the headband is very thin, then use simmering water for less time. And if the headband is very thick, then extend the time by half a minute or so. Generally, I always do it for exactly 2 minutes. Time goes very slowly standing there waiting for the 2 minutes to pass, just like on the Stairmaster. Make sure not to let the headband touch the sides or bottom of the pan or it will melt and mar in that place.
After two minutes, take the headband out and while it is still warm and pliable, gently press in down on the top to flatten it a little, because Blythe's head is a little flatter on top and not quite round.
Next, dike of the ends of the headband to the desired length.
Finally, I file the end to smooth it out so that it doesn't scratch my girl's head. Sometimes after filing, I dip the ends back in the boiling water and then touch up the ends again with the file. That just makes it extra smooth. All done.
Here is a template to download. I made this as a suggestion from someone on Blythe Kingdom. I guess that you could hold up your work in progress to the template to check for size and shape. I hope this helps you have success in the beginning. But you should play around a little with the length. I make some of them 1/4 to 1/2 inch longer depending on how much hair I want it to hold back or even based on the type of original headband.
This size of headband is a very good fit for American Girl dolls, too. I suppose that you could rework or repeat the steps to make them smaller for other dolls, like SD size BJDs, though I haven't tried that myself, yet.
And if this all seems like too much work for you, then most of the head bands pictured are for sale in my Etsy shop, along with the outfits pictured. There are Halloween themed outfits, too! Boo!