Rinse excess dye from the fabric using cool water, either in a sink or in a washing machine set to delicate.
Bring several gallons of water to a simmer in a large pot. Add a squirt of liquid castile soap when the water begins to simmer.
Submerge the Batik painting in the pot of water, using a wooden spoon to push the fabric down into the water. Allow to simmer until a large amount of wax has floated to the surface of the pot.
Lift a portion of the fabric from the pot with a wooden spoon and inspect for wax residue. Continue checking until it appears that all the wax has been removed from the fabric and then resubmerge and allow to simmer for another minute.
Turn off the heat under the pot and allow it to cool completely until the wax floating on the top of the water has hardened. Lift the wax from the top of the pot and discard.
Remove the fabric from the pot and rinse with cool water, either in a sink or a washing machine set to delicate. Smooth the fabric out on a flat surface and allow to air dry completely.