Encourage children to think of someone they should forgive.
Talk about how we feel when we are hurt and angry. It hurts us, but we can ask God to help us give up those feelings.
Put the tablets in the water and ask the children to imagine asking God to help them forgive. As the bubbles begin to detach from the tablets, imagine that you give the hurt feelings to God. The tablets take a while to dissolve, which also illustrates that sometimes it takes time to forgive. The water may also have changed colour, which illustrates that it is not as if the thing that hurt you had never happened, it was just changed by God.
Remind the children that Joseph chose to forgive his brothers. Despite the harm they had done to him, Joseph was able to see the fulfillment of his dream.