Paper and Printing Recipes / A Handy Volume of Practical Recipes, Concerning the Every-Day Business of Stationers, Printers, Binders, and the Kindred Trades

by John Sawtelle Ford

To Make Invisible Writing.

To make secret or invisible writing, procure some very thin starch, with which write with a quill pen (which should be a soft one) anything that fancy may dictate. Suffer it to dry perfectly; examine the paper upon which you have written, and not one letter can be distinguished by the naked eye. Procure a little iodine, which is an elementary body, dissolve it in water, and with a camel’s hair pencil, a quill, or any other convenient article, dipped in the solution, slightly rub the paper on the side which has been written upon; the writing will instantly appear as distinctly visible as if written with the finest ink ever invented.