Goldenrod paper will turn from yellow to red in the presence of a base such as a bicarbonate or dilute ammonia solution. Bob Becker has designed several ways to write messages for his students using goldenrod paper. He either writes a message with wax or by using clear cellophane tape onto the paper. The wax and cellophane protect the surface of the goldenrod paper so when it is sprayed with ammonia gas all the paper except where the letters exist will change to red and you see yellow print. Bob has also made goldenrod paper red with bicarbonate solution and allowed it to dry. By printing in wax or using cellophane tape onto the red paper he can spray the paper with vinegar and it will turn yellow in the background and the printing will appear yellow.