Materials Needed: White painting paper, watercolor paint, baking soda, paintbrushes, and painting T-shirts.
Instructions: Before the children paint with the watercolor paint, you must first make the mystery picture. You can have the children watch you make the mystery picture. Tell them they will see their mystery picture after they paint the picture with watercolor paint. To make the mystery picture, dissolve four tablespoons of baking soda with four tablespoons of water in a cup. Use a cotton swab or paintbrush and dip it in the mixture. Paint a pumpkin design on each sheet of white paper. Make sure the mystery picture is completely dry before giving it to the children.
Once the mystery picture is dry, give each child the paper. Have the children put on their painting T-shirt. Tell the children there is a mystery picture on the paper. In order for them to see it, they must paint the paper with watercolor paint. Give each child a paint brush and have them paint their paper with orange or yellow paint. As they paint, the water and baking soda mixture will resist the watercolor paint, and the mystery picture will be revealed.