Melting wax crayons

At the start of last year, we made some new chunky crayons by recycling broken bits of smaller crayons and melting them into moulds.  I wasn't sure if my eldest remembered that, but I was very sure the little one didn't, so I thought we could try something different but with the same science behind it - using heat to change crayons from solids to liquids. 

This time we peeled the paper off some cheap wax crayons, lined them up on a small canvas (you could use thick cardboard) and put cotton string (note, don't use the sort of string that melts with a bit of heat!) around them to secure in place.

Crayons strung around a canvas

We talked about how the crayons stayed the same shape (aside from when you draw with them and rub a bit off!) because they are solid.  I asked how we could make them drip to make a picture and my eldest thought we should heat them.  I gave him a hairdryer to give it a go, with the canvas propped at an angle against a wall so the drips would run down it, and put a wad of paper underneath so any drips wouldn't run into the radiator underneath!  I quickly realised that a 4 year old and hair dryer was a recipe for wax being splattered all over the wall, so put a big sheet of paper behind the canvas - I'd suggest starting with something similar (cardboard better as it doesn't blow) in place!

Melting the wax

The little one watched on as the big one heated the crayons and we saw them turn into a liquid that changed shape into droplets and ran down the canvas.  He kept going until we had a rainbow (well, we didn't start at red, so it's not really in wavelength order) of wax running down the paper.  Then we stopped and let it solidify - the drips no longer ran once it cooled down.  We talked about how water can change state too, at zero degrees Celsius, from solid to liquid and vice versa, but that wax melts or turns into a solid at a higher temperature.

Wax melted and then solidified

Once solid, we carefully removed the remains of the crayons, and then turned the canvas upside down and I gave the boys the hairdryer to turn the lumpy remnants of crayons into drips going the other way, leaving a lovely colourful bit of science-based art for our wall!  As there was less wax to splatter, this was a better time for my 2.5 year old to take control of the hairdryer! 

We're going to melt the remaining pieces of crayon into moulds to make some chunky rainbow crayons, which change colour as you draw and wear away different bits of the wax, like we did before.