you have to heat set the colors into the blocks---we use brown paper (like a brown paper sack) place the block on the ironing board- you can put paper towels down first if you are worried about the wax seeping through)
then you put the brown paper on top and heat set with a hot iron- the brown paper will absorb the excess wax while the hot iron will set the colors.
then they need to be set aside to *cure*
they should not be washed for at least 24 hours-
then wash in cold water
we have always used regular crayons-
the preschool makes one every year- the ones that are now 10 years old have faded a bit- but they just re-color them to make them vibrant again.