As per usual with these projects, I used Sculpey polymer clay.
I also used a temporary tattoo. I got mine from one of my favorite authors, who my friend met. I also understand that you can get similarly cool ones as free handouts from cons, comic-cons, and dentists offices. Anywhere you get it, if you like it enough to want to be able to wear it more than just a day or a week, read on.
I rolled a ball of it to smush. The trick to this is that, unlike usually where you just go with however big you want it to be to look good, with this you also need it the right size to fit your entire temp tattoo on it, so make sure you do that.
Because I wanted this to me pretty uniform in shape, and to definitely be clean-ish, I rolled my ball out with a round marker. If you're super advanced, or just like crafty toys, a pasta machine would also work for this (MAKE SURE you do NOT use the same one for your clay and your actual pasta/food).
I like my pendants being about 1/8" thick. However, as I will discuss in a bit, you may want your thicker for structural reasons.
I placed my oval-shaped pendant into the tine that it would be baking in. Note that I punched its hole before putting it in there.
As you can see, this is the correct size for the temp tattoo that I chose.
I applied the tattoo to the clay as per the instructions for application to skin.
Remember not to get hasty or impatient with this part- leave the wet cloth on the correct amount of time, and peel off the paper carefully. If you do, then it should come out just about perfectly, like so.
Because this is polymer clay, the water shouldn't be there while it's baking, or it could inhibit the proper curing of the clay, so try to dry it off/out as much as possible. DO NOT try to dry off the surface of your clay with a cloth, as the tattoo will stick to your cloth at this point, messing up your currently-awesome design.
Honestly, don't be too worried about the water. Get out what you can, leave the rest. Let it sit in the sun if you're worried about it a lot.
Bake it according to the baking directions. I baked mine about 8 minutes.
As you can see, the tattoo is now cracked, but it has cured along with the clay, and shouldn't come off unless you really scrape at it.
Your pendant is now finished, but keep reading for more tips and etc.
Fingernail polish... such a benignly evil little thing. Those of you who may or may not work with Polymer clay a lot probably know what is coming...
Becuase I wanted to protect the pendant that I had made (understandably, I think), I coated it in this stuff...
It created a really cool effect, and I let it dry and coated it again. However, here is the issue with this: fingernail polish, unless it explicitly says "acrylic" on it, is solvent based. This means that it will stay tacky OR it will dry, but it will eventually eat at your clay piece, OR it will dry, but get tacky 6 months later.
So, long story short, while the rest of this tut is a good thing, DO NOT use fingernail polish on it, unless you only want it for a year or two.
Use Varathane or Future Floor Polish. This is not an endorsement, and they are hard to find, but really your pendant is/should be fine without it anyway.
In any case, I think it turned out looking really nice. I just added a jump ring to the top, and put it on a leather cord from a different necklace that I had lying around.
A note on structural stability: polymer clay is very ahrdy, and can/will hold up to a lot of abuse. However, it may feel/seem odd to you to find that large, flat objects still remain somewhat flexible after baking. I myself thought it was odd that my pendant was still somewhat 'bendy', even after I put it back in the oven to harden some more, and let it cool a bunch.
The fact of the matter is, this elasticity makes it last longer and better, because it can handle abuse like being dropped much better than hard clay. However, if you want your pendant not to be able to bend, construct it differently- make it thicker, but mesh/screens/wooden pieces/coins (maybe a quarter?) in there, and it will help with the structural integrity. Ultimately, though, you just need to remember that you are working with an elastic clay, and it will bend some.