I saw this idea a long time ago on Tumblr, what to do with your broken crayons...
I thought "hey that's a cute way to recycle old crayons" and had to try it myself! So I went out to Walmart and bought a heart shaped silicone mold (from the Valentines Day section) for only $3.50! You can go to Hobby Lobby or Micheal's for them too, or for different shaped molds. Since its Valentines Day coming up I thought I would make hearts.
All you do it take your broken down crayons, take off the wrapper if it has any, and break the crayons in 1/2 inch size pieces or smaller to fit and melt down faster in the mold. You fill each mold to the top or how ever thick you want your crayons to be, of different colors. The thicker you want them the longer it will take to bake. What I did was took about 8 crayons to make it bigger, I would say for most 4-6 crayons should be plenty. Turn your oven on to 250 degrees, and put your mold with crayons in for 20 minutes, if you used a smaller amount (4-6 crayons) start at 15 minutes and keep checking to see if the crayons are melted. Also use a baking sheet to but the mold on so when you grab it, it wont dump all over or get messy. Once they are melted, take them out of the oven and let them cool on a flat surface. Once they are cool and hard, just flip them out of the silicone mold and THERE YOU HAVE IT!! :)
This is a super easy, fun craft for the kids! Perfect for birthday party favors, school valentines, to keep kids entertained at a wedding, or just something fun they can color with!