John Daniels, age 15, of Nashua, N.H., for his question:

HOW IS LITMUS PAPER MADE?

Litmus paper is a material that can be used to tell whether a solution is either acid or alkaline. Litmus paper, manufactured primarily in Holland, is made by dipping unglazed paper in a litmus solution and then letting the paper dry. Litmus is a blue coloring matter that is obtained from the juices of certain lichens. Lichens are fungus growths.

Either red or blue litmus paper can be made by proper treatment.

The lichens are mashed in a trough. The pulp produced is then mixed with ammonia and other substances and allowed to ferment. It forms into blue powdery lumps, which are made into tablets. The tables then can be redissolved in water to turn litmus back into solution form.

If you dip a piece of blue litmus paper into vinegar, lemon juice or a solution of boric acid, the color of the paper will change from blue to red because these substances are all acids. If a piece of red litmus paper is dipped into ammonia water, solutions of borax or washing soda, the color will change from red to blue because these substances are alkaline.