Polymer Clay is such a fun medium to work with, always learning new things and having a better understanding of every aspect of the art.  People always tell you to use an oven thermometer and to preheat your oven but no one tells you WHY!  Well I finally figured that out, when I put my convection oven on and watch the oven thermometer after a short time the heat spikes, I had it on 250 and it was 350!  No wonder my clay would darken and smell like burned plastic, now everything looks great, no smell.  Cindy Lietz suggest to bake it for 60 minutes to make it stronger, I thought that was too much but I would test my pieces and know Cindy is right, and I was worried about it darkening but I see that's not happening.  Another thing Cindy advises to putting card stock over to cover, I use cardboard from food packaging, making sure no printing touching my clay, my pieces have never looked better, thanks Cindy!  Here are Hello Kitty Pendants I made for my great nieces.