I haven't done a proper Instructable for a while. Here is my attempt to correct that...
Working with resin isn't new and there are loads of tutorials. That being said, one thing that I try to do, is make the complex a bit more simple. Honestly this is really easy...
To begin with you're going to need resin. What I use is a two part expoy resin called West System. There are loads of different types out there, but for me this has worked well. Whatever you get make sure it dries clear
Epoxy Resin (or Casting Resin)
Paint Shaving ( Or you can cast, wires, cotton balls, paper towels, crayons, glitter or whatever.) As long as it is free of moisture
Barrette hardware (I bought mine on Etsy)
Hot Glue Glue
Step 1: Casting the Resin
Mix up some resin, pour it into a mold and add your material you want to cast.
The mold here is a silicone container used for holding glue. Silicone molds are a great choice as the cured resin doesn't stick to them. After you've poured the resin you might find some air bubbles.
Use you heat gun to evenly apply a light heat. This will draw the bubbles to the top and remove them from your casting. It works great, but go slow, as over heating the resin will cause the opposite effect and leave you with a bubbled over mess.
Step 2: Bending Your Casting
One of the really cool properties of wood is that you can bend it. You simply steam wood and it bends.
Why not cured resin? I'd never seen it done, but it sure seemed like it should work. And it did!
I used my heat gun to apply even heat over the cast paint shaving and after a good 5 minutes it was plyable and quite soft.
Ahead of time I had taken a small block up wood and cut a curve in it. Now. I simply sandwiched the cast paint shavings in that block and clamped it in place.
Wait for it to cool for a couple of hours.
Step 3: Shaping, Sanding & Finishing
Once the casting is cool, you're done.
At that point you really have a completed hair clip if your mold was the shape you liked. In my case the mold was a rectangle and I was hoping for more of an oval look.
So I took it to the band saw and shaped it. After that I took it to the belt sander and refinded that shape.
Because of that I had to sand it. If I hadn't needed to do the shaping and sanding, there would have been no reason to sand and polish, because the casting came out of the mold with a very high gloss.
For sanding, I wet sanded from 400 grit to about 12000 grit. I took about an hour, but brought the piece back to it's high gloss.
The last step was simply hot gluing on the hair clip and taking a few pictures. In this case hot glue is a great choice, and it bonds well to the resin.
I've included a video, which adds some details, but glosses over other bits.
Please feel free to ask questions, I'll do my best to answer them.