Last week we decided to make some melted crayon canvases. There's some great youtube videos showing the process. So, the kids were excited and we picked up some canvases and several boxes of 64 count crayolas. After many days, Thomas finally finished arranging his crayons and we got started.
I glued the crayons on the canvas with a glue gun. After getting about 8 glued down I realized I hadn't payed any attention to which direction the labels were facing. And, if you let your kids help you by placing the crayons on the glue, they won't either. I did try to keep them all lined up, although it wasn't perfect.

Once the canvas was ready to go we got out a large painting tarp to protect the area around the canvas. Don't skip this! The wax will drip off the bottom of the canvas and will easily be blown off either side. You can use cardboard, drop clothes, anything that's thick enough for the wax not to go through.
We did this one inside, but I would recommend melting wax outside. I would guess, similiar to encaustics, you don't want to have fumes lingering in your house.
Next, we tried several sources of heat. Thomas wanted to keep the drips more in lines than splattered all over the place. We first tried a Martha Stewart heat gun. I wasn't really happy with how it started, so we grabbed the hairdryer from upstairs. It blows more air than a heat gun, so your drips will be splatters.
The hairdryer was going kinda slow, so we added my Ranger Heat It heat gun. BINGO! The Ranger gun was the best - hands down - and we soon switched off the hairdryer. I think we melted for about 15 - 20 minutes, including switching tools.

What we discovered:
The area of the crayon you're melting makes a difference. We got the best melting by holding the gun pointed at the middle of the crayon. If you hold it too high, then you loose the nice clean top. Too low and the point drips away.
Also, the direction of the heat. If the heat is applied from below, then the drips don't want to go down. By varying the direction of the heat you can cause the paint to flow straight or splatter to either side.
And here's the finished canvas:
