For this instructable you will need:
A canvas (Cardboard or similar will work as well)
Crayons, lots of them!
A glue gun
Cardboard and paper
A printer or drawing equipment
A heatgun or hairdryer
Step 1: Step 1: Skin Those Crayons!
Make sure you have enough crayons to cover the top side of you canvas. Remove the paper casing from the crayons.
Step 2: Step 2: Stick 'em Down
Stick the skinned crayons along the top of your canvas. I found it is easiest to put down a little bit of glue where you plan to stick the crayon and press it into it instead of applying the glue to the crayon first.
Warning - Glue guns are hot, be careful!
Step 3: Step 3: Prepare the Picture
There are a couple of ways of going about this. You can draw a picture onto a piece of paper or print one off. Once you have a picture (it doesn't have to be silhouetted, that's just a personal preference), stick it onto a piece of cardboard with pritt stick glue or something similar. Carefully cut around the picture. Depending on how thick your cardboard is, you may need to stick the cut out onto another piece, you double the thickness.
Now, stick the picture onto the canvas with the glue gun. Make sure you glue around the whole of the picture, leaving no gaps, especially along the top side. This creates a seal between the picture and the canvas, so no wax can drip through.
Another tip is to cover the top side of the cardboard cut-out with tape, perpendicular to the picture itself. This will stop wax dripping through the holes in the cardboard.
Step 4: Step Four: the Melting
This is the best part of the process, the melting. Put your heat gun/hair dryer on a high heat setting (and low-blow if you an). Heat the crayons until the wax starts to drip. You can guide the wax down the canvas to a certain extent, causing it to go in particular places or just allow it to flow freely, it's up to you.
When you are happy with the dripping patterns, gently remove the tape and give the area a quick heat to settle the wax into place.
Ta-da, your wax art is complete!