Remove false hairpieces, bobby pins, elastics and any other items that are in your hair, and loosen the bun with your fingers. Put on a waterproof smock, and hang your head over a sink that has a water spray attachment.
Pour pineapple juice or vinegar on your scalp, and saturate your hair with it as much as possible.
Dig your fingers into the solid gelatin to reach your hair's roots. Massage the pineapple juice or vinegar into your hair, starting at the roots and working your fingers down to the ends of your hair, for about two minutes.
Kneel slightly in front of the sink with your head forward, and let your friend soak your scalp and hair with hot water. Pull your fingers through your hair while your friend rinses out the pineapple juice or vinegar your poured in it, along with the pieces of gelatin. Rinse your hair until all of the pineapple juice or vinegar is gone. Have your friend inspect your hair to see how much gelatin remains.
Repeat Steps 2, 3 and 4 as needed until all of the gelatin is gone.
Shampoo and condition your hair as usual.