New Invisible Ink
C. Wideman communicates a new method of making an
invisible ink to Die Natur. To make the writing or drawing appear
which has been made upon paper it is sufficient to dip it in water. On
drying the traces disappear again, and reappear again at each
succeeding immersion. The ink is made by intimately mixing Linseed Oil
one part. Water of Ammonia twenty parts, Water 100 parts. The mixture
must be agitated each time before the pen is dipped into it, as a
little of the oil may separate and float on top, which would, of
course, leave an oily stain upon the paper.