Place peeled and broken crayon pieces in molds. Overfill the molds (especially if they are smaller hearts). The crayons melt to fill every empty space.
Put silicone mold on a cookie sheet before putting it in the oven.
Place in oven and cook for 8-12 minutes. Time may vary.
Once you see that the crayons have fully melted, pull them out of the oven immediately.
The wax will be very hot and liquid. How long your newly formed crayons need to cool will depend on the size of your molds.
Once one is completely cool to the touch, you can carefully push them out of the silicone mold.
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Notes
Adult supervision is required! Don't leave young children unattended with hot wax.
Pull out crayons as soon as you see the wax fully melted.
The hot wax will take around 20-30 minutes to harden and cool.
Cook time will vary depending on the size of your broken pieces and your oven settings.
If there is one stubborn crayon with the melted wax, you can use a toothpick to stir the wax in the mold.